Chemistry of Ash and 

Leachates from the 

May 18, 1980 Eruption of 

Mount St. Helens, Washington

A. Chemical and Mineralogic Aspects of 

Observed Fractionation of Ash from the 

May 18, 1980 Eruption of Mount St. Helens

B . Leachate Chemistry of Ash from the

May 18, 1980 Eruption of Mount St. Helens

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1397"
Chemistry of Ash and 

Leachates from the 

May 18, 1980 Eruption of 

Mount St. Helens, Washington

TODD K. HINKLEY, Editor

A. Chemical and Mineralogic Aspects of 

Observed Fractionation of Ash from the 

May 18, 1980 Eruption of Mount St. Helens

By TODD K. HINKLEY, KATHLEEN S. SMITH, 

JOSEPH E. TAGGART, JR., and JULIA T. BROWN

B . Leachate Chemistry of Ash from the

May 18, 1980 Eruption of Mount St. Helens

By TODD K. HINKLEY and KATHLEEN S. SMITH

With a section on LABORATORY METHODS DEVELOPED FOR 

MOUNT ST. HELENS WATER AND ACID LEACHING STUDIES

By STEPHEN A. WILSON and CAROL A. GENT

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1397

Data and interpretation, 

from a large suite of 

well-documented samples 

from the explosive eruption

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1987
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging-in-Publication Data

Main entry under title:

Chemistry of ash and leachates from the May 18, 1980 eruption of Mount St. Helens, Washington.

(U.S. Geological Survey professional paper ; 1397)

Includes bibliographies.

Supt. of Docs, no.: I 19.16:1397

1. Volcanic ash, tuff, etc. Washington (State) Saint Helens, Mount Region Analysis. 2. Saint Helens, 

Mount (Wash.)-Eruption, 1980. I. Hinkley, Todd K. (Todd King) II. Series 

QE461.C426 1986 552'.23 85-600226

For sale by the

Books and Open-File Reports Section

U.S. Geological Survey

Federal Center

Box 25425 

Denver, CO 80225
CONTENTS

[Letters designate the chapters]

Page

(A) Chemical and mineralogic aspects of observed fractionation of ash from the May 18, 

1980 eruption of Mount St. Helens, by Todd K Hinkley, Kathleen S. Smith, Joseph 

E. Taggart, Jr., and Julia T. Brown ................................... V

(B) Leachate chemistry of ash from the May 18, 1980 eruption of Mount St. Helens, by

Todd K. Hinkley and Kathleen S. Smith ............................... 23

ill

Chemical and Mineralogic Aspects of 

Observed Fractionation of Ash from the 

May 18, 1980 Eruption of 

Mount St. Helens

By TODD K. HINKLEY, KATHLEEN S. SMITH, 

JOSEPH E. TAGGART, JR., and JULIA T. BROWN

CHEMISTRY OF ASH AND LEACHATES FROM THE MAY 18, 1980 

ERUPTION OF MOUNT ST. HELENS, WASHINGTON

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1397-A

CONTENTS

Page

Abstract ........................................... 1

introduction ........................................ 1

Acknowledgments ................................... 1

Sample collection .................................... 2

Laboratory methods ................................. 3

Discussion and results ............................... 3

Postdepositional wind winnowing of ash ............. 3

Variation in chemical and mineralogic composition of ash

with distance from source and through time of fall . . 3

Mineral chemistry involved in fractionation .......... 8

Discussion and results Continued

Artificial fractionation of ash samples ...............

Mechanisms of fractionation of ash .................

Summary ..........................................

References cited .....................................

Appendix A. Complete tabulation of analytical results for 

whole ash .....................................

Appendix B. Estimate of analytical error in chemical concentration data for whole ash .......................

Page

10

11

14

14

18

22

ILLUSTRATIONS

Page

FIGURE 1. Sampling localities map ................................................................................. 2

2. Photograph showing postdepositional wind winnowing of ash ................................................. 3

3. Map showing distribution of SiO2/Fe2Og and SiO2/MnO values ................................................ 5

4. Chart showing changes in chemical composition of ash through time of fall at Almira, Wash., and Missoula, Mont. ... 7

5. Photographs showing depositional stratigraphy of ash ....................................................... 11

TABLES

Page

TABLE 1. Major-element composition of dark- and light-colored fractions of ash separated by postdepositional wind winnowing . 4

2. Range in concentration of oxides with distance from source .................................................. 6

3. Major-oxide composition of ash in time-sequence samples, Almira, Wash., and Missoula, Mont., May 18 and 19 ...... 6

4. Comparison of maximum observed chemical fractionation of ash through time of fall at Almira, Wash., and Missoula, Mont.,

	and with distance from the volcano .................................................................. 8

5. Minor- and trace-element composition of ash in time-sequence samples, Almira, Wash., and Missoula, Mont., May 18 and 19 9

6. Major-element and mineralogic composition of Wilfley table ash fractions, Ritzville, Wash. ........................ 12

7. Major-element and mineralogic composition of Wilfley table ash fractions, EUensburg, Wash. ..................... 13

8. Chemical variation with eolian fractionation in ash from eruption of Quizapu in South America, 1932 ............... 14

VII

CHEMISTRY OF ASH AND LEACHATES FROM THE MAY 18, 1980 ERUPTION OF

MOUNT ST. HELENS, WASHINGTON

CHEMICAL AND MINERALOGIC ASPECTS OF OBSERVED FRACTIONATION 

OF ASH FROM THE MAY 18, 1980 ERUPTION OF MOUNT ST. HELENS

By TODD K. HlNKLEY, KATHLEEN S. SMITH, JOSEPH E. TAGGART, JR., and JULIA T. BROWN

ABSTRACT

We present a large body of data on major-, minor-, and trace-element 

compositions of whole-ash samples from the May 18, 1980 eruption 

of Mount St. Helens. Samples were collected from a broad downwind 

area during and shortly after deposition. Their postdepositional history 

and circumstances of collection are thoroughly documented.

The data yield a picture of distinct chemical and mineralogic fractionation within the ash-fall blanket that conforms well to expectations of either atmospheric sorting or changes in ash composition 

during eruption. This fractionation is manifested in the following ways.

1. In most places, the ash blanket consists of two or more strata of 

different density and color.

2. In general, the high-density dark particles are depleted with increasing distance from source.

3. At two sites, samples collected during time of fall in abutting time 

increments show a decrease through time in the concentrations 

of oxides MgO, CaO, Ti02, and Fe2O3. These oxides are 

associated with the high-density particles, such as opaque 

minerals, pyroxene, amphibole, and calcic plagioclase. The samples 

also show an increase through time in the oxides SiO2, K2O, and 

Na2O, associated with the low-density particles, such as sodic 

plagioclase and glass.

The range in the chemical composition of the ash blanket appears 

to be greater as a function of distance from source than as a function 

of time of fall. This suggests that atmospheric sorting processes may 

have caused more variation in composition of samples from the ash 

blanket than was caused by differences in composition of ash erupted 

from the vent.

INTRODUCTION

In one of the most significant geologic events of the 

twentieth century in the United States, the May 18, 

1980 eruption of Mount St. Helens, Wash., beginning 

at 8:32 a.m. PDT, distributed an estimated half billion 

tons of air-fall tephra over a large area of Washington, 

Idaho, and Montana (Sarna-Wojcicki, Meyer, and 

others, 1981). From a geologic viewpoint, the eruption 

was unusual in that it was large, and it was a lateral 

blast (Hoblitt and others, 1981; Mullineaux and

Crandell, 1981). From a social viewpoint, the eruption 

was of interest in that it resulted in the greatest loss 

of life from a volcanic eruption in United States history, 

and in that the ejecta fell on a populated area (Schuster, 

1981; Klein, 1981; McKnight and others, 1981; Gough 

and others, 1981). From the viewpoint of opportunity 

for study, the eruption was unusual in that, in contrast 

to most large eruptions throughout the world, the ejecta 

fell on easily accessible land and not on water. Detailed study of the eruption and its ejecta may help in 

forecasting the nature and effects of future events 

(Decker, 1981).

In this report, we present a large body of data on the 

major-, minor-, and trace-element compositions of 

samples that constitute a large suite of whole-ash 

samples from the May 18 eruption, collected over a 

broad area of deposition and well documented with 

respect to their postdepositional history and circumstances of collection. We also describe some of the 

horizontal and vertical differences in composition of the 

depositional ash blanket from the May 18 eruption, as 

seen from samples collected at varying geographic locations, and from samples collected at two sites during 

time of fall in abutting time increments during the first 

19 hours of deposition. The observed compositional 

variations over distance and through time are consistent with expectations of atmospheric sorting of the ash 

as well as with expected changes in composition of ash 

produced from the vent that may have occurred during the eruption.

ACKNOWLEDGMENTS

We thank Jon J. Connor, Harry A. Tourtelot, and Ray 

E. Wilcox for scientific discussions that affected the 

course of the research. We would like to acknowledge

1
CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

124° 123° 122° 121° 120° 119° 118° 117° 116° 115° 114°

100 MILES 

FIGURE 1. Sampling localities, Washington, Idaho, and western Montana.

Ardith Bartel, J. S. Wahlberg, and James Baker, who 

worked on the X-ray analyses; F. E. Lichte and George 

Riddle, who worked on the inductively coupled plasma 

spectroscopy analyses; D. B. Hatfield, who worked on 

the chemical analyses; and R. E. McGregor, who managed the sample preparation. Samples collected very 

shortly after time of fall were provided by on-site colleagues of the U.S. Geological Survey and other organizations, and by private individuals. These include Mr. 

Burton, Herb Chapman, Ken Cochran, Russ Collett, 

Carol Connor, Robert Curry, Larry Gough, Ellen Hall, 

Paul Hammond, Neil Harrington, Ed Heffern, Willard 

Henning, Mr. Hintze, Thor Kiilsgaard, Steve Luthy, 

Dan Mueller, Janet Peard, Donnie Rambo, Ronald 

Severson, Hansford Shacklette, Wyatt Silker, Anita 

Tarbert, Judith Weiss, Spencer Wood, Joe Zimmer, the 

Montana Air Quality Bureau, and the Randle, Wash., 

Ranger District. Without the help of these individuals 

and organizations this study could not have been

conducted as it was. Special thanks to Mr. and Mrs. 

Homer Evers of Almira, Wash., who collected and 

documented a set of samples in abutting time increments throughout the period of fall, and to Paul Strater 

of Yakima, Wash., who preserved transparent-walled 

cups of fallen ash for observation of contrasting strata.

SAMPLE COLLECTION

Climactic eruptive activity began at 8:32 a.m. PDT 

on May 18, 1980. Injection of large amounts of ash 

material into the atmosphere continued for about 9 

hours (Christiansen and Peterson, 1981). Downwind 

from the volcano, the intense period of ash fall may have 

lasted somewhat longer than 9 hours. Samples of ash 

from the May 18 eruption were collected in Washington, 

Idaho, and western Montana (fig. 1), and Colorado and 

Kentucky, by resident volunteers and on-site colleagues
CHEMICAL AND MINERALOGIC ASPECTS OF FRACTIONATED ASH

during or immediately after deposition, and by us 

several weeks later. Two time-sequence sample suites 

(one consisting of two samples collected at Missoula, 

Mont., by Steve Luthy, and another of five samples collected at Almira, Wash., by Mr. and Mrs. Homer Evers) 

were graciously made available to us. In this report we 

refer to these suites as the time-sequence samples.

A complete tabulation of all chemical data from all 

samples, with a coded explanation of source location, 

exposure history, and other information, is presented 

in Appendix A. Of 59 original samples, 10 were split for 

analysis in duplicate, making a total of 69 samples.

LABORATORY METHODS

Chemical analyses were performed in U.S. Geological 

Survey analytical laboratories using XRF (X-ray 

fluorescence) spectrometry for major elements and ICP 

(inductively coupled plasma) spectroscopy for minor and 

trace elements (Taggart and others, 1981). Anionic 

species were determined by 1C (ion chromatography). 

The samples were analyzed in a partially random order, 

so that any systematic errors, or drift in the instrument 

readings through a long analytical sequence, would be 

effectively converted into random error. Semiquantitative mineralogic analyses were made using X-ray 

powder diffractometry. Appendix B lists the geometric 

errors for reported concentrations with each element.

DISCUSSION AND RESULTS 

POSTDEPOSITIONAL WIND WINNOWING OF ASH

At some sampling localities and at sufficiently long 

times after deposition, wind winnowing of an initially 

homogeneous or distinctively structured ash layer can 

segregate the bulk ash into physically separate fractions 

that are distinct in their appearances and compositions. 

We comment on this process here because it may have 

affected the composition of many samples collected for 

this study and for several other chemical studies of the 

Mount St. Helens ash that we cite. An example of the 

appearance of dark- and light-colored fractions of ash 

separated by wind winnowing on the ground is 

presented in figure 2. In many areas throughout the 

region of ash deposition, appreciable portions of the 

light-colored fine fraction may have been blown away 

before samples were collected for various investigative 

projects, including this one. The size and shape of the 

zones of light-colored, fine-grained fractions, and "saltand-pepper," coarse-grained fractions are determined by 

the fine topography on the ground (vegetation in

FIGURE 2. Postdepositional wind winnowing of ash. Ash is 

segregated by wind into light-colored, fine-grained and salt-andpepper, coarse-grained fractions.

photograph), as it provides zones of higher and lower 

wind intensity. At sites in eastern Washington, windwinnowed fractions were clearly distinct to a field 

observer. The opaque and dark minerals were strongly 

concentrated in the dark fraction. Plagioclase and glass 

were moderately enriched in the dark- and light-colored 

fractions, respectively, but both phases are major constituents in both fractions. Data showing the contrasting compositions of the two wind-separated 

fractions are presented in table 1.

Samples that may have been affected by wind winnowing on the ground have not been incorporated into 

our summary tables that illustrate contrasts in chemical 

composition with varying distance from the volcano or 

through time of fall (tables 2-5). Samples that may have 

been affected by wind winnowing on the ground are 

identified in Appendix A by the letter "L" (indicating 

"late") as the initial character of their eight-character 

sample identifier code. Samples unaffected by wind winnowing are coded beginning with the letter "O" which 

indicates "original."

VARIATION IN CHEMICAL AND MINERALOGIC

COMPOSITION OF ASH WITH DISTANCE FROM

SOURCE AND THROUGH TIME OF FALL

We observed a systematic fractionation of the ash into layers of high-density, dark-colored particles and 

layers of low-density, light-colored particles. This pattern of fractionation conforms well to expectations of 

either atmospheric sorting (by particle density, size, and 

shape) or compositional changes during eruption. In 

general, the ash blanket consists of two or more layers 

of contrasting light and dark appearance. Plagioclase
4 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

TABLE 1. Major-element composition of dark- and light-colored fractions of ash separated by postdepositional wind winnowing

[Fraction data in percent. Ratios for Connell site calculated from average of No. 1 and No. 2 dark-colored fraction values. LOI, loss on ignition]

Connell, Wash.

Components

Si02

Fe 20 3

MgO

CaO

Na 20 

K20 

Ti02

P 2°5 

MnO

LOI

Dark

No. 1

60.1 

18.7

5.6

2.6

6.4

4.4 

1.0 

.79

.20 

.08

.4

fraction

No. 2

58.8 

18.0

7.1

3.1

6.3

4.2 

1.0 

1.00

.20 

.09

.5

Light 

fraction

64.1 

16.7

5.2

2.0

4.7

4.5 

1.4 

.73

.20 

.07

.6

Ellenshurg, Wash.

Dark 

fraction

56.9 

18.7

7.3

3.9

7.1

4.1 

.72 

.90

.20 

.11

.3

Light 

fraction

63.3 

16.9

5.5

2.3

5.0

4.4 

1.34 

.75

.20 

.08

.5

Ratio light: dark

Connell

1.08 

.91

.82

.07

.74

1.05 

1.40 

.81

1 

.82

.75

Ellensburg

1.11

.90

.75

.59

.07

1.07 

1.86 

.83

1

.73

.6

and glass were also fractionated, the heavier plagioclase 

being more abundant than the glass in the dark layers. 

Observations by Hooper and others (1980) indicated 

that the dark ash "is composed predominantly of 

plagioclase crystals * * *, glass which varies from 

colorless to dark brown and which usually included 

abundant microlites, and composite lithic fragments of 

plagioclase and glass. Crystals of titanium-rich magnetite make up to 5 to 10 percent (by volume), and crystals 

of basaltic hornblende form about one percent by 

volume. Occasional crystals of orthopyroxene are present. The pale ash is composed of about 80 percent clear 

glass, * * * plagioclase is the principal crystalline 

phase in this ash as well, but smaller crystals of iron 

oxide and hornblende are present." This fractionation 

is a function of both (1) increasing distance from source, 

as seen within the depositional blanket at each sampling 

locality, and (2) time of fall, as seen between the individual time-sequence samples.

The chemical composition of the ash changed 

systematically with distance from the volcano; particles 

of greater density and more ferromagnesian composition are depleted in the ash with increasing distance 

from the volcano. The relationship between some 

chemical constituents of the ash associated with the 

darkness and density of the particles may be seen in 

figure 3, which shows plots of ratios between SiO2 

(which is low in dark minerals, intermediate in 

plagioclase, and highest in glass) and the metal oxides 

Fe2O3 and MnO (which are abundant in dark and dense 

minerals). Away from the main axis of the plume (SarnaWojcicki, Meyer, and others, 1981), this trend of changing dark-mineral content is less distinct. Very close to

the volcano (the Mount St. Helens and Randle Ranger 

District sites), the dumping of coarse fragments made 

representative sampling difficult, and samples (provided 

by on-site colleagues) were of widely varying appearance 

and composition. Data for 10 major and minor oxides 

in ash at eight sites at increasing distances from the 

volcano are presented in table 2.

Fractionation in chemical composition of the ash with 

distance from the volcano has been reported by others 

(Fruchter and others, 1980; Hooper and others, 1980). 

Both their work and our work demonstrate that the 

change in chemistry with distance from source is irregular. This irregularity could be due to any of the

following.

>

1. Local irregularities in atmospheric transport processes such as wind directional velocity changing 

the trajectory of similar particles, and local winds 

of varying direction winnowing out finer material 

as the plume altitude decreased and it approached 

the level of the ground.

2. Changes with time in the composition of the ash 

plume emanating from the volcano.

3. Sampling error due largely to sampling difficulties 

associated with the layered compositional segregation of the ash blanket, as well as later wind winnowing of the ash as it lay on the ground.

This last consideration may have been significant when 

samples were collected for us by others, with the goal 

of obtaining material as soon as possible after deposition. Taylor and Lichte (1980) acknowledged this potential problem and urged that interpretations be based 

on multiple samples.
124'

CHEMICAL AND MINERALOGIC ASPECTS OF FRACTIONATED ASH

122° 121° 120° 119° 118° 117° 116° 115°

0 100 MILES 

EXPLANATION

SiO2/Total Fe as Fe2

9-<11 

1 1-<14

1 6- < 1 9

O3 SiO2/MnO

590-781 

>781-962 

>962-1,163 

>1, 163-1,350

FIGURE 3. Distribution of values of two chemical ratios that reflect silicic versus ferromagnesian character of the ash. Values in percent. 

Contours apply to values for both ratios and are approximately located; dashed where location increasingly uncertain.

There was also a modest but consistent variation in 

the chemistry of the ash through time of fall, at Almira 

and Missoula (fig. 1), where our time-sequence samples 

were collected. Figure 4 presents the changes in concentration of eight major oxides in the ash of the timesequence samples from Almira and Missoula; the 

equivalent numerical data are presented in table 3. 

Fe2O3, MgO, and CaO decrease through time for each 

of these samples. The magnitudes of the decreases expressed as fractions of the maximum values are 18 percent, 26 percent, and 18 percent, respectively. The 

differences in the behavior of these three oxides, as influenced by atmospheric effects, are due to previously

mentioned points 1 and 2. SiO2 , K2O, and Na2O increase through time of fall, and the magnitudes of their 

increases are 4.8 percent, 21 percent, and 4.4 percent, 

respectively. In general, the degree of chemical fractionation (compositional range) in these constituents is 

greater in the suite of samples collected at increasing 

distance from the volcano (Mount St. Helens to 

Missoula, table 2) than in the time-sequence sample 

suites collected at Almira and Missoula (table 3). This 

variation in degree of fractionation is shown in table 4. 

Only for Na2O and CaO is the observed fractionation 

over distance not clearly larger than the fractionation 

through time of fall.
CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

TABLE 2. Range in concentration of oxides with distance from source 

[Data in weight percent. All samples collected prior to first post-ash-fall rain. Fe2C> 3 is total Fe calculated as Fe2C> 3]

Approximate 

Sampling distance from S±Q M Q p Q M Q CaQ Q 

location Mount St. Helens 2 2 3 2 3 & 2 

(km)

Randle

Randle (split)

Ritzville 

nnup7ui n ____

Spokane 

nrujci> V5 n

Plummer

Emida 

ODIEMC30 

Emida (split) 

ODIEMC3X 

Coeur d'Alene 

ODICAE10 

St. Maries 

ODISMC10 

St. Maries (split) 

ODISMC1X - 

Missoula 

ODMMIL40 -----

48 62.0 16.8 5.19 2.3 5. 

48 62.3 17.0 5.18 2.2 5.

314 66.7 16.2 4.04 1.5 4. 

398 66.5 16.5 4.07 1.5 4. 

426 66.9 16.0 3.78 1.3 3.

441 67.2 16.0 3.70 1.3 3. 

441 67.4 16.0 3.71 1.3 3.

444 66.4 16.1 3.99 1.5 4.

456 67.0 16.0 3.72 1.3 3. 

456 66.7 16.0 3.71 1.3 3.

631 64.6 16.5 4.22 1.6 4.

26 4.4 

23 4.4

09 4.5 

27 4.5 

85 4.6

85 4.7 

86 4.6

09 4.4

92 4.6 

91 4.6

58 4.4

K n T-I n P n rtvl llUo 9 ^

1.34 

1.35

1.63 

1.59 

1.69

1.70 

1.70

1.72

1.69 

1.67

1.53

0.71 0.2 

.71 .2

.58 .2 

.58 .2 

.54 .1

.53 .1 

.53 .1

.58 .2

.54 .1 

.53 .1

.61 .2

MnO

0.07 

.07

.06 

.06 

.05

.05 

.05

.05

.05 

.05

.06

TABLE 3. Major-oxide composition of ash in time-sequence samples, Almira, Wash., and Missoula, Mont, May 18 and 19 

[Data in weight percent. Exact times of beginnings of ash fall not available. Split sample divided for analytical replication. Fe2O3 is total Fe calculated as Fe2O3]

Time of fall

Oxides that increase 

through time of fall

Si0 2 K2 0 Na 2 0 MgO A

Oxides that decrease 

through time of fall

1 2°3 CaO Fe 2 0 3 Ti02

Almira, Wash.

Until 2 p.m. PDT May 18-

2-3 p.m. PDT 

3-4 p.m. PDT ----- 

3-4 p.m. PDT (split) 

4-6 p.m. PDT - - 

6 p.m. PDT May 18, until

8 a.m. PDT May 19 

61.4 1.28 4.3 2.3 

61.3 1.27 4.3 2.3 

61.7 1.36 4.3 2.1 

61.4 1.32 4.3 2.3 

62.4 1.38 4.4 2.1

64.4 1.50 4.5 1.7

17.3 

17.3 

16.7 

17.1 

16.7

16.4

5.57 

5.62 

5.25 

5.41 

5.22

4.61

5.35 

5.33 

5.05 

5.12 

5.04

4.38

0.74 

.74 

.68 

.70 

.68

.60

Missoula, Mont.

Until 9 p.m. PDT May 18- 

After 9 p.m. PDT May 18-

63.6 1.46 4.4 1.9 

67.7 1.72 4.6 1.2

16.7 

16.0

4.92 

3.80

4.52 

3.59

0.66 

.52
CHEMICAL AND MINERALOGIC ASPECTS OF FRACTIONATED ASH

2.5

2.0 -

1.5 -

I 1.0 

(D

0.5

MgO

_._._.r~

-f -

TiO,

Fe203

6.0

5.5

5.0 2

UJ

O 

DC

4.5

SiO,

5.5

5.2

K 2 O

Na2O

4.0

65

61

4.5 

4.3

O

U

1 p.m. 2 p.m. 3 p.m. 4 p.m. 

MAY 18, 1980

5 p.m. 6 p.m. v 8 a.m.

MAY 19, 1980

FIGURE 4. Changes in chemical composition of ash through time of fall at Almira, Wash., and Missoula, Mont. Arrow

at one end of each curve points to the appropriate scale.

Table 5 presents the data for the suite of minor and 

trace elements determined in the Almira and Missoula 

time-sequence samples, grouped by those elements that 

increase and those that decrease during time of ash 

deposition. Published data on minor and trace elements 

in minerals are less abundant than on major elements, 

and trace-element concentrations vary with mineral 

paragenesis. Cobalt, chromium, and nickel are associated with the early-deposited opaque minerals, 

manganese and zinc with pyroxene and amphibole, and 

strontium with plagioclase. Tabulations by SarnaWojcicki, Meyer, and others (1981) of composition of 

glass fraction and bulk ash confirmed that concentrations of barium and uranium are higher, and those of

cobalt, chromium, manganese, nickel, scandium, 

vanadium, and zinc lower, in the glass than in the bulk 

ash.

Fractionation with distance (table 2) is sufficiently irregular that it may be improper to use the high and low 

values to define the range in a sample suite when those 

high and low values do not occur at or near the geographic ends of the line along which the samples were 

collected. Irregular values in table 2 could result from 

unrepresentative sampling of the stratified ash blanket, 

either before or after wind winnowing of ash on the 

ground. No such problems are suspected in the timesequence samples from Almira or Missoula. The expected analytical error of the XRF method used to
8 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

TABLE 4. Comparison of maximum observed chemical fractionation 

of ash through time of fall at Almira, Wash., and Missoula, Mont, 

and with distance from the volcano

[Values are differences, in percent, between highest and lowest values, expressed relative 

to the high value. Fe O. is total Fe calculated as Fe.OJ

Components

Difference through 

time of fall

Almira Missoula

Maximum difference

between any two

sites sampled

Si02

A1 2°3

Fe 2°3

MgO

CaO

Na 20

K2°

Ti0 2

4.8

5.2

18

26

18

4.4

21

19

6.1

4.2

21

37

29

4.3

15

21

7.5

5.9 '

28

43

26

4.3

22

25

determine the major elements reported in table 3 for the 

time-sequence samples is smaller than the differences 

reported between the two split samples from the 

3-4 p.m. PDT Almira ash sample; the differences were 

probably due to inhomogeneities of sample in the containers from which the aliquots were taken. Division of 

samples into aliquots for the XRF and ICP analytical 

procedures was done on the samples in their original 

state, without diminution and homogenization by grinding: this was so in most cases because little sample 

material was available, and because of initial plans for 

use of total sample. Imprecision of a magnitude comparable to that reported between the two splits of the 

3-4 p.m. PDT sample may be inferred to occur in all 

of the major-element data of this report. The precision 

for the ICP method used to determine the minor and 

trace elements reported in table 5 probably is poorer 

than that of the XRF method used for major oxides. 

The differences between the duplicate analyses of the 

3-4 p.m. PDT Almira sample, however, are smaller than 

the changes through the suite.

The Almira site, where five time-sequence samples 

were collected during deposition, is north of the main 

plume axis. As figure 3 illustrates, the ash deposited 

at the margins of the plume tended to be less fractionated than at nearby points on the main axis. SarnaWojcicki, Shipley, and others (1981) reported that dark 

ash (correlating with their unit 1) began to fall considerably before the light-colored ash (unit 3). In 

Pullman, Wash., southeast of Almira and Ritzville, dark 

ash fell from 2:00 p.m. PDT until between 5:15 and 5:30 

p.m. PDT, when observers noted an abrupt change to 

a visibly lighter colored ash (Hooper and others, 1980). 

The known trajectory of the plume of suspended

ejecta, its spatial density and composition, and 

meteorologic conditions during and after the eruption 

are discussed by others (Pollack, 1981; Hobbs and 

others, 1981; Danielsen, 1981; Vossler and others, 1981). 

A bimodality in grain-size distribution and a "secondary 

thickening" in the ash layers on the ground are discussed by Brazier and others (1983). The size and shape 

of the ash particles, the methods of determining these 

parameters, and the implications for atmospheric 

transport fractionation are discussed in detail by Zielinski and Sawyer (1981).

MINERAL CHEMISTRY INVOLVED 

IN FRACTIONATION

Our approach to explain the major-oxide fractionations observed in the time-sequence samples (fig. 4 and 

table 3) and with distance is to discuss each oxide in 

terms of the minerals in which it is abundant. This approach can also explain the artificial fractionations 

made on the Wilfley table (see "Artificial fractionation 

of ash samples" section) and the fractionations observed 

in other eruptions (see discussion of Larsson's work in 

"Mechanisms of fractionation of ash" section).

Fe2O3 The decrease in Fe2O3 concentration through 

time of fall (fig. 4) may be associated with changes in 

the abundance of dense magnetite (FeO Fe2O3 ) and ilmenite (FeO TiO2), and to some extent the pyroxenes 

of the idealized enstatite-ferrosilite series 

(MgO SiO2-FeO SiO2), although the reported composition of the pyroxenes is closer to the magnesian end 

member. A calcium-free pyroxene of composition 0.8 

MgO-SiO2-0.2 FeO-SiO2 has 13.5 percent FeO and 18 

percent MgO.

MgO The decrease in MgO concentration through 

time of fall (fig. 4) may be associated with changes in 

the abundance of the magnesian pyroxenes and of hornblende. The MgO contents of the five hornblendes 

tabulated by Deer and others (1967) are 10, 13, 15, 18, 

and 21 percent, indicating that hornblende, a minor constituent, may be as rich in MgO as any species in the 

ash.

CaO The decrease in CaO concentration through 

time of fall (fig. 4) cannot be explained on the basis of 

changes in abundance of any single phase of extremely 

high CaO concentration, but must be ascribed to the 

net effect of several changes in mineral abundance involving both major and minor phases of the ash. The 

magnitude of the decrease in CaO concentration in the 

samples is slightly less than the decrease of Fe2O3 and 

MgO (17 percent for CaO, versus 18 percent and 26 percent for Fe2O3 and MgO, respectively). The possible 

changes in mineral abundance that could cause the
CHEMICAL AND MINERALOGIC ASPECTS OF FRACTIONATED ASH 9 

TABLE 5. Minor- and trace-element composition of ash in time-sequence samples, Almira, Wash., and Missoula, Mont, May 18, and 19

[Data in ppm. Leaders I I. data Dot available]

Time of fall

Elements that increase 

through time of fall

Elements that decrease 

through time of fall

Ba Li Zr Co Cr Mn Ni Sc Sr Zn

Almira, Wash.

Until 2 p.m. PDT May 18-

2-3 p.m. PDT ----- 

3-4 p.m. PDT - ----- 

3-4 p.m. PDT (split) - 

/i _A TI m onT _ __ _

320 

310 

335 

330 

i^s

23 

22 

24 

24

OA

1.7

16

00

120 

120 

120

120

i Tn

14 

14 

14

15

i /.

21 

18 

21 

21

1 7

730 

715 

675 

715 

7nn

21 

19 

19

20 

on

12 

11 

10 

11 

i i

530 

515 

490 

510 

^r\^

91 

90 

84 

88 

«A

78 

77 

73 

76

7A

8 a.m. PDT May 19----- 365 29 11 140 11 13 620 13 445 70 70

Missoula, Mont.

Until 9 p.m. PDT May 18- 

After 9 p.m. PDT May 18-

360 

380

25 

30

11

20

150 

150

12 

8

21 

8

630 

510

19

7.5

10 

8

470 

365

76 

51

70 

62

observed changes with distance in CaO abundance in 

the ash blanket, and through time of fall, are as follows.

1. The early deposition and (or) early eruption of 

plagioclase relative to glass. Plagioclase and glass 

are much more abundant in the bulk ash than any 

other constituents, therefore fractionation between 

them could produce appreciable differences in CaO 

concentration within the ash blanket, limited by the 

differences in their CaO concentrations and by the 

degree of fractionation. Plagioclase of composition 

50 mole percent anorthite contains about 10 percent CaO, in contrast to about 5 percent CaO in 

average bulk ash from Almira. All dark and opaque 

minerals in the ash (amphibole, pyroxene, 

magnetite, ilmenite) would be removed by precipitation through air in preference to plagioclase. 

However, plagioclase generally crystallizes earlier 

than glass during magmatic differentiation, and 

plagioclase should be preferentially deposited with 

respect to glass, especially pumiceous glass that 

contains about 2.76 percent CaO (Sarna-Wojcicki, 

Shipley, and others, 1981). Most plagioclase grains 

observed in the ash are zoned, with zones ranging 

in composition from 40-60 mole percent anorthite. 

If there is variation in whole-grain calcium content 

of plagioclase grains, there would be a calcium differentiation effect in the ash due to the grains' differing atmospheric settling rates, especially if the 

more calcic grains were larger.

2. Early crystallization or settling from air, or both, of 

hornblende. Hornblende is less dense than 

magnetite or ilmenite. Its density overlaps that of 

pyroxene, and it is more dense than plagioclase and

glass. The five hornblendes tabulated by Deer and 

others (1966) contain 12, 11, 13, 5, and 13 percent 

CaO (order corresponds to list previously given for 

MgO concentrations), contrasting with 5 percent 

in average bulk ash from Almira. Presence of hornblende may affect concentration of CaO in the ash 

that was deposited either close to the volcano or 

moderately early in the ash blanket. 

The early eruption or deposition from suspension in 

air of the CaO-poor minerals magnetite, ilmenite, 

and hypersthene-enstatite. Melson and Hopson 

(1981) gave CaO concentrations in three ilmenites 

from samples of the May 18 eruption as 0.11, 0.22, 

and 0.10 percent, and in magnetites from the same 

samples as 0.09, 0.12, and 0.09, respectively; Deer 

and others (1966) gave the CaO content of three 

pyroxenes of the enstatite-ferrosilite series as 0.23, 

1.4, and 1.4 percent. In figure 4, the first-collected 

time-sequence sample from Almira appears to be 

slightly lower in CaO concentration than the second 

sample (5.57 versus 5.62 percent), whereas the CaO 

concentration decreases strongly through the remainder of the samples (5.33, 5.22, 4.61). This slight 

reversal in trend is due to the dominance of the 

calcium-poor minerals magnetite and ilmenite in the 

first-collected fraction, contrasted with the increased amount of hypersthene and calcic plagioclase in the second-collected fraction. In the 

subsequent fractions, which contain little of any 

opaque or ferromagnesian minerals, the amounts 

of calcic plagioclase decrease regularly. Paralleling 

the initial increase and subsequent steady decrease 

in CaO concentration in the time-sequence samples
10 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

from Almira, the same pattern occurs in the 

samples from both Ritzville and Ellensburg that 

were artificially separated on the Wilfley table 

(tables 6 and 7). The densest fraction of the Wilfley 

table separates from Ritzville (table 6) contained 

1.4 percent CaO and was shown by X-ray diffraction analysis to contain only magnetite, ilmenite, and hypersthene, in order of decreasing 

abundance.

Al2O3 The decrease in A12O3 concentration through 

time of fall (fig. 4) may be associated with the early eruption or deposition of plagioclase relative to glass. 

Plagioclase that is 50 mole percent anorthite has 28 percent A12O3. Sarna-Wojcicki, Meyer, and others (1981) 

reported A^C^ as 15 percent in the glass fraction of the 

ash near Mount St. Helens. The calcic component of 

plagioclase is enriched either close to the volcano or 

early in the time sequence, and sodic plagioclase is more 

abundant farther from the volcano or later in the sequence, as judged from chemistry; but because plagioclase of some type may be well distributed throughout 

the sequence, A12O3 does not change its concentration 

as markedly as other major oxides discussed in the 

following. Sarna-Wojcicki, Meyer, and others (1981, 

table 82) reported aluminum concentrations in glass of 

14.7 and 13.8 percent, when expressed as A12O3. The 

A12O3 concentration of the bulk ash containing the latter glass was given as 16.8 and 16.0 percent, in two 

splits. This is about 22 and 16 percent more aluminum 

in the bulk ash than in the glass, in the two splits, 

respectively.

TiO2 The decrease in TiO2 concentration through 

time of fall (fig. 4) may be associated with the early settling or eruption of ilmenite, FeO TiO2 .

Concentrations of three major oxides increase 

through time of fall in the time-sequence samples 

SiO2, K2O, and Na2O. The magnitude of the increases 

as fractions of the maximum values are 4.7,15, and 4.4 

percent, respectively. The increases in all three oxides 

are consistent with preferential mineral deposition from 

air in the following order: opaques (magnetite and 

ilmenite), ferromagnesian silicates (pyroxene and hornblende), plagioclase, and glass. For SiO2 the concentration would be anticipated to increase at each 

succession in the sequence of phases just listed, and the 

same should be true for Na2O, although the increases 

in Na2O through the mineral series are less even. K2O 

is concentrated in the glass phase and nearly absent 

from all of the others, except for a probable fraction of 

1 percent in hornblende. This known contrast in K2O 

concentration between glass and all other phases is consistent with the greater observed magnitude of fractionation for K2O through time of fall in the 

time-sequence samples than for SiO2 or Na2O.

ARTIFICIAL FRACTIONATION OF ASH SAMPLES

Samples of bulk ash from Ritzville and Ellensburg, 

Wash., were separated by water winnowing on a Wilfley 

table into fractions of different particle density to determine whether a hypothesis of physical winnowing of a 

source ash of uniform composition would be consistent 

with the observed fractionation of the ash over distance 

or through time of fall Separation was not done on the 

time-sequence samples of ash from Almira or Missoula 

because of insufficient sample. Using artificial separation, we wanted to obtain a suite of samples that would 

have a greater compositional range than that of suites 

of natural samples, giving as great a separation by 

mineral grain types as possible, but still differentiated 

by a process analogous to the atmospheric processes 

that may have acted on the ash during deposition. Semiquantitative mineralogic analysis was done on some of 

these fractions and on magnetic and nonmagnetic subfractions of them. Major-oxide composition and 

mineralogy of the Wilfley table separates from the two 

sites are presented in tables 6 and 7.

More fine material was present in ash from the Ritzville area than from the Ellensburg area, and most of 

the fine material from both sites was lost during the 

separation. The Ellensburg sample was subject to 

greater wind winnowing on the ground, and may have 

lost its fine fraction before collection; the Ritzville sample was sheltered by wheat rows. In addition, it is also 

possible that low-level winds caused winnowing as the 

ash fell to the ground. Sarna-Wojcicki, Shipley, and 

others (1981, p. 587 and 588) observed that low-level 

wind vectors were "* * * 10°-90° north of the highlevel wind vectors * * *" and that "Downwind in central Washington, eyewitnesses reported a sharp 

southern boundary to the falling ash, which was coarse 

to medium sand size. The fine ash was winnowed northward toward the axis of the air-fall lobe. Size analysis 

of ash samples confirm eyewitness observations." 

Several centimeters of ash were deposited on both areas. 

No close correspondence in character or composition of 

material is claimed between Ritzville and Ellensburg 

fractions that have the same fraction sequence number 

in tables 6 and 7; however, the expected changes in 

abundance of high- and low-density minerals (and glass) 

are observed through the sets of subsamples that were 

collected in succession from the Wilfley table, for both 

the Ritzville and Ellensburg materials. The analyses 

show that the ash is dominantly plagioclase (40-60 percent anorthite content) and glass, and that it has a suite 

of two heavy opaque minerals, magnetite and ilmenite, 

and two moderately heavy ferromagnesian minerals, orthopyroxene and hornblende. All mineralogic determinations of this study were done on Wilfley table
CHEMICAL AND MINERALOGIC ASPECTS OF FRACTIONATED ASH 11

fractions rather than on any whole-ash samples, in order 

to minimize mineral interference effects.

MECHANISMS OF FRACTIONATION OF ASH

In our work, we have observed two modes of natural 

fractionation (with distance from source, and through 

time of fall) and one kind of artificial fractionation 

(water winnowing on a Wilfley table) of the Mount St. 

Helens ash. Also available to us is a set of photographs 

(fig. 5) showing the appearance of the density stratification in the ash as seen through the transparent walls 

of nearly cylindrical plastic cups into which ash fell at 

Yakima, Wash. These samples were preserved and 

photographed by Paul Strater. The complexity of the 

stratigraphy in these well-preserved samples may indicate that in some localities air-fall deposition was more 

variable than outlined by Sarna-Wojcicki, Meyer, and 

others (1981) and Waitt and Dzurisin (1981). The strong 

visible contrasts between alternating strata indicate 

either that the atmospheric sorting effects during time 

of fall were strong and rather oscillatory, or that there 

were strong (and oscillatory) changes in ash composition from the volcano, or that there was great overhead 

wandering of a plume differentiated into lateral zones 

of contrasting composition.

Hooper and others (1980), Taylor and Lichte (1980), 

Fruchter and others (1980), and Sarna-Wojcicki, Meyer, 

and others (1981) have all discussed aspects of the 

observed differentiation of the ash blanket on the 

ground. In accounting for the differentiation, some 

authors favored changes in the composition of the 

material produced from the volcano and others favored 

atmospheric sorting. Hooper and others (1980) proposed 

that the bimodal nature of the ash implies two separate 

source materials, the dark ash possibly derived from a 

part of the old volcanic cone dispersed in the initial explosive event, and the pale ash representing new 

magma. Taylor and Lichte (1982) said that evidence 

seen by them implies that differentiation of the ash occurred after eruption as the ash travelled eastward 

through the air. Fruchter and others (1980) wrote that 

general compositional trends are evident with increasing distance from the volcano, especially with respect 

to silica, iron, calcium, magnesium, titanium, and 

manganese. They cited a variability in proportions of 

glass and crystalline species in samples from various 

locations. Their main ash composition tables are arranged by increasing distance from the volcano. SarnaWojcicki, Meyer, and others (1981) discussed both possible sorting mechanisms as well as separate compositional stages of the eruption.

FIGURE 5. Depositional stratigraphy of ash in transparent-walled 

collection vessels. Photography by Paul Strater.
12 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON 

TABLE 6. Major-element and mineralogic composition of Wilfley table ash fractions, Ritzville, Wash.

[Data in weight percent. Mineral composition determined by X-ray diffraction. Value for Fe2Og in most dense fraction (in parentheses) is semiquantitative. All mineral data are semiquantitative. Fe2O3 is total Fe calculated as Fe2Og. Leaders ( ), data not available; n.d., mineral not detected; tr, trace amount; P, parameter present in unknown amount; (P), parameter 

probably present; U, undifferentiated fraction; M, magnetic subtraction; N, nonmagnetic subtraction; LOI, loss on ignition]

Components

CiO _

A1 2°3 

Fe 2°3 

Mg0 

MO r\ _

K o 

P n P 2°5 

vfw^n

Percent of total 

recovered -----

Orthopyroxene 

Plagioclase 

U

M 

N

U 

M 

N

U 

M 

N

U

M 

N

U

M 

N

U 

M 

N

U 

M 

N

Most d 

1

13.0 

3.33 

(64.3) 

3.52 

1.44 

.75

.24 

13.6 

.64 

.44

^ 1 QQ

99.38

.17 

50-57

35-47 

8 

n.d. 

n.d. 

n.d. 

n.d.

2345

61.6 67.9 71.2

19.6 16.1 16.2 

4.18 3.32 3.15

1.69 1.10 1.04 

6.33 3.70 3.43

4.57 4.59 4.66

1.10 1.73 1.81 

.61 .47 .44

.15 .15 .15

.05 .05 .04

.48 .67 .60

100.16 99.78 100.72

51.8 28.9 9.3 3.0

2 tr tr n.d. n.d. 

i ^ on L J £. U

tr

2 n.d. n.d. n.d. n.d.

n.d. 

n.d. 

2 20-30 n.d. n.d. n.d. 

n.d. 

n.d. 

2 20-3Q n.d. n.d. n.d. 

n.d. 

n.d.

2tr 14 15 10.5 

17-21 

40

2n.d. 1 1 1.3 

1-2 

5-10

2n.d. P P P 

n.d. 

n.d.

-.east dense fraction 

6 7

69.7 71.6 

15.4 15.9 

3.05 3.03 

.99 1.00 

3.04 2.99 

4.58 4.65

1.92 1.93 

.42 .41 

.13 .13 

.05 .05 

.93 .65

100.21 102.34

2.05 4.84 

(P) n.d.

n.d. n.d. 

n.d. n.d. 

n.d. n.d. 

12 10 

0.7 0.7 

P P

This value represents an increase on ignition and indicates a change in the oxidation state of 

the iron species.

This set of values represents a subfraction with specific gravity greater than 2.85.
CHEMICAL AND MINERALOGIC ASPECTS OF FRACTIONATED ASH

TABLE 7. Major-element and mineralogic composition of Wilfley table ash fractions, Ettensburg, Wash.

13

[Data in weight percent. Due to inadequate sample size, fractions 4 and 5, and 6 and 7, were combined for analyses. Mineral composition determined by X-ray diffraction. All mineral 

data are semiquantitative. Fe2Og is total Fe calculated as Fe2O3. Leaders ( ), data not available; n.d., parameter not detected; tr, trace amount; P, parameter present in unknown 

amount; (P) parameter probably present; U, undifferentiated fraction; M, magnetic subtraction; N, nonmagnetic subtraction; LOI, loss on ignition]

Components

^ r\ _ _

A1 2°3 

T?Q n _ _ Fe 2°3

MgO 

pa fi __ . _ _ _

Na 20 

Kr»_ __ ._ _ _

fi O _ _ ._ _ .

*2°5 

Kfi-i r\

T r»T

Percent of total

i icigiic; u J- u c;

Orthopyroxene 

1 -Ldg-L Ul_ -Lao t.

v^Lld 1. U£f

U

M 

N

U 

M 

N

U 

M

N

U 

M 

N

U 

M

N

U

M 

N

U 

M 

N

1

47.4

6

0

24.4

1 O C.

4

f\ C

1.48

.35

2.72

.64

OQ

102.34

1 C Q

21 

n.d.

(P) 

n.d.

P 

P

n.d. 

19-20

n.d. 

P

n.d. 

n.d.

n.d. 

n.d.

2

CO 0

20.9 

5.41

3.24 

7.64

4.35

.70

.69

.14

riQ

1£

102.21 

7n s

9

n.d.

(P) 

4

67

2-3

3

C.t 1

4.06

i 70

6

00

H . J /

1.11

.55

.17

.06

.45

101.77 

13.2

6

15 

4

n.d. 

n.d.

(P) 

(P) 

(P)

n.d. 

n.d.

32

26 

51

2-3

tr 

2

n.d. 

n.d.

4 and 5 6 and 7

£Q 1

15.1 

4.26

1 . £.7

3.10

4.53

1 HR 

.66

. L.L.

.07

07 _

QQ OR _

0.13 and 0.03 0.11 and 0.01

(P) n.d.

n.d . n.d .

f\f O O

2 0.7

P n.d.
14 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

Larsson (1937) carefully documented compositional 

differences in the ash deposited over a broad region 

after the eruption of the Chilean volcano Quizapu. 

Samples collected from an irregular array of geographic 

points rather than in a strict distance progression from 

the source were arranged in an order yielding a progression of compositional changes attributable to fractionation by either atmospheric winnowing or by changes in 

ash composition during eruption. His data are presented 

in table 8. Larsson attributed the entire observed effect 

to the atmospheric mechanism and seemingly regarded 

it only as a scientific curiosity with some interesting 

implications that the observed fractionation is similar 

to what might be expected of magmatic differentiation. 

He stated (p. 46, provisional translation by Ray E. 

Wilcox): "If the differentiation * * *[of the Quizapu 

ash] is compared with a corresponding magmatic variation diagram, for the normal magma of the calc-alkalic 

suite, it is interesting to find a correlation between 

them, even as to some details. Indeed, the active agent 

of differentiation, gravitation, is the same in both cases. 

That which in the one case is brought about in a short 

time in an especially fluid medium requires a much 

longer time in the second case in a very viscous 

medium." Larsson discussed in some detail the presumed changes in mineralogic abundance that are expected to cause the measured changes in chemical 

composition.

In the present study, our observations of fractionation with distance and through time of fall, the Wilfley 

table water-winnowing data, and the stratigraphic 

record observed in plastic cups are all consistent with

TABLE 8. Chemical variation with eolian fractionation in ash from 

eruption of Quizapu in South America, 1932

[Data in weight percent. Modified from Larsson (1937), by permission; la and Ib are from 

the same site; higher-number sites have smaller depositions! thicknesses on the ground 

(Larsson's identifying codes). Leaders ( ), data not available]

Sites

Components

la Ib

Si02

Ti02

A1 20^

Fe 2°3

FeO

63.79

.78

16.20

2.92

1.40

64.55

.72

15.61

1.77

2.06

67.45

.45

17.28

1.37

.90

69.78

.46

15.44

.75

1.59

70.20

.60

14.86

.96

1.26

MnO

MgO

CaO

Na2 0 

K20

.11

1.06

3.87

5.91 

2.83

.13

1.28

3.06

6.87 

3.37

.09

1.05

3.15

4.76 

3.20

.60

2.12

4.41 

3.91

.06

.54

1.88

4.46 

4.43

fractionation due to either changes in magma composition or atmospheric sorting. If, as would be consistent 

with the simplest conceptual model, we postulate that 

most of the chemical progression in the time-sequence 

samples were due to a compositionally variable source, 

and most of the changing chemistry with distance were 

due to atmospheric sorting, it would follow from the 

magnitude of range in our data for the two types of sample suites that atmospheric sorting processes were of 

greater importance in fractionating the ash.

SUMMARY

1. The air-fall tephra samples of this study are extremely well documented, and represent a favorable 

geographic array. Most samples were collected very 

shortly after time of fall. Whole-rock chemical 

analyses were performed with care and by appropriate and reliable methods. The samples and 

the data derived from them are appropriate for further study of this important eruption and for comparison with other air-fall tephra blankets.

2. In most places, the ash blanket consists of two or 

many more strata of different density and color, 

and in some localities the stratigraphy resulting 

from air-fall deposition may have been more 

variable than reported by others.

3. The dense, dark particles are, in general, depleted 

with increasing distance from source.

4. The range in the chemical composition of the ash 

blanket is greater, although much less regular, as 

a function of distance from source than as a function of time of fall. This suggests that atmospheric 

sorting processes played a stronger role in differentiating the tephra blanket than did change in composition of material ejected from the source.

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p. 115-119.

Christiansen, R. L., and Peterson, D. W., 1981, Chronology of the 1980 

eruptive activity, in Lipman, P. W., and Mullineaux, D. R., eds., 

The 1980 eruptions of Mount St. Helens, Washington: U.S. 

Geological Survey Professional Paper 1250, p. 17-30.

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Geological Survey Professional Paper 1250, p. 815-820.
CHEMICAL AND MINERALOGIC ASPECTS OF FRACTIONATED ASH 15

Deer, W. A., Howie, R. A., and Zussman, J., 1966, An introduction to 

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Hobbs, P. V., Radke, L. F, Eltgroth, M. W, and Hegg, D. A., 1981, 

Airborne studies of the emissions from the volcanic eruptions of 

Mount St. Helens: Science, v. 211, p. 816-818.

Hoblitt, R. P., Miller, C. D, and Vallance, J. W, 1981, Origin and 

stratigraphy of the deposit produced by the May 18 directed blast, 

in Lipman, P. W, and Mullineaux, D. R., eds., The 1980 eruptions 

of Mount St. Helens, Washington: U.S. Geological Survey Professional Paper 1250, p. 401-420.

Hooper, P. R., Herrick, I. W, and Laskowski, E. R., 1980, Composition of the Mount St. Helens ash fall in the Moscow-Pullman area 

on 18 May 1980: Science, v. 209, p. 1125-1126.

Klein, J. M., 1981, Some effects of the May 18 eruption of Mount St. 

Helens on river-water quality, in Lipman, P. W, and Mullineaux, 

D. R., eds., The 1980 eruptions of Mount St. Helens, Washington: 

U.S. Geological Survey Professional Paper 1250, p. 719-732.

Larsson, Walter, 1937, Vulkanische Asche vom Ausbruch des 

Chilenischen Vulkans Quizapu (1932) in Argentina gesamelt Eine 

Studie uber aolische Differentiation: Geological Institute of Upsala, Bulletin 26, p. 27-52.

McKnight, D. M., Feder, G. L., and Stiles, E. A., 1981, Effects on a 

blue-green alga of leachates of ash from the May 18 eruption, in 

Lipman, P. W, and Mullineaux, D. R., eds., The 1980 eruptions 

of Mount St. Helens, Washington: U.S. Geological Survey Professional Paper 1250, p. 733-742.

Melson, W. G., and Hopson, C. A., 1981, Preemption temperatures and 

oxygen fugacities in the 1980 eruptive sequence, in Lipman, P. 

W, and Mullineaux, D. R., eds., The 1980 eruptions of Mount St. 

Helens, Washington: U.S. Geological Survey Professional Paper 

1250, p. 641-648.

Mullineaux, D. R., and Crandell, D. R., 1981, The eruptive history of 

Mount St. Helens, in Lipman, P. W, and Mullineaux, D. R., eds., 

The 1980 eruptions of Mount St. Helens, Washington: U.S. 

Geological Survey Professional Paper 1250, p. 3-16.

Pollack, J. B., 1981, Measurement of the volcanic plumes of Mount 

St. Helens in the stratosphere and troposphere Introduction: 

Science, v. 211, p. 815-816.

Sarna-Wojcicki, A. M., Meyer, C. E., Woodward, M. J., and Lamothe, 

P. J., 1981, Composition of air-fall ash erupted on May 18, May 

25, June 12, July 22, and August 7, in Lipman, P. W., and 

Mullineaux, D. R., eds., The 1980 eruptions of Mount St. Helens, 

Washington: U.S. Geological Survey Professional Paper 1250, 

p. 667-681.

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Daniel, and Wood, S. H., 1981, Areal distribution, thickness, mass, 

volume, and grain size of air-fall ash from the six major eruptions 

of 1980, in Lipman, P. W., and Mullineaux, D. R., eds., The 1980 

eruptions of Mount St. Helens, Washington: U.S. Geological 

Survey Professional Paper 1250, p. 577-600.

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operations in the Pacific Northwest, in Lipman, P. W., and 

Mullineaux, D. R., eds., The 1980 eruptions of Mount St. Helens, 

Washington: U.S. Geological Survey Professional Paper 1250, 

p. 701-718.

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Mullineaux, D. R., eds., The 1980 eruptions of Mount St. Helens, 

Washington: U.S. Geological Survey Professional Paper 1250, 

p. 683-687.

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11, p. 949-952.

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v. 211, p. 827-830.

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from the May 18 eruption Stratigraphy and field sedimentology, 

in Lipman, P. W., and Mullineaux, D. R., eds., The 1980 eruptions of Mount St. Helens, Washington: U.S. Geological Survey 

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81-114, 20 p.

APPENDIXES A AND B
18 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

APPENDIX A. COMPLETE TABULATION OF ANALYTICAL RESULTS FOR WHOLE ASH

[Major and minor elements in whole-ash samples, reported as oxides, were determined by X-ray fluorescence spectrometry after sodium metaborate fusion. Trace elements in whole-ash 

samples were determined by inductively coupled plasma spectroscopy after hydrofluoric acid digestion. These techniques are described by Taggart and others (1981)]

Coding key for eight-character sample identifiers for ash samples analyzed is as follows:

Character 1. O="original," collected by on-site colleagues immediately after deposition 

L="later," collected by authors weeks after deposition

Character 2. D=not rained on before collection ("dry")

R=exposed to rain before collection ("rain")

Character 3. Initial of State in which sample was collected: W=Washington, I=Idaho, C=Colorado, M=Montana, and K=Kentucky

Characters 4 and 5. City or town or other name for locality:

AL=Almira 

CA=Coeur d'Alene 

CO=Connell 

CR=Columbia River

basin

DE=Denver 

EL=Ellensburg 

EM=Emida 

GL=Glasgow 

HA=Harrison

Character 6. Collector of sample: 

B=Mr. Burton 

C=Russ Collett 

E=Ellen Hall 

H=Ed Heffern 

K=Thor Kiilsgaard 

L=Steve Luthy

HE=Helena 

LE=Lewistown 

MC=Miles City 

MI=Missoula 

ML=Moses Lake 

PL=Plummer 

RA=Rest area, 18 

miles east of 

Ellensburg 

RI=Richland

M=Dan Mueller 

P=Paul Hammond 

Q=Air Qual. Bur. 

R=Ken Cochran 

S=Wyatt Silker 

T=Anita Tarbert

RL=Ralston

RR=Randle Ranger District

RZ=Ritzville

SG=Sprague

SH=Mount St. Helens

SM=St. Maries

SP=Spokane

UC=Union City

YK=Yakima

YV=Yakima VaUey

V=Homer Evers 

W=Willard Henning 

X=Hansford Shacklette 

Y=Donnie Rambo 

Z=Kathleen Smith

Character 7. Sample number of sub-location number, if more than one sample was collected by a single collector at the site identified by 

characters 4, 5, and 6.

Character 8. An "x" indicates that sample is one member of a duplicate pair (analytical split). In each duplicate pair one sample is labelled 

"x", the other "o". All samples not split for duplicate analyses are labelled "o".

BULK ANIONS

[Values in ppm]

Sample Cl NO, PO/ SO/ Sample Cl NO, PO; SO/

ODWALV10

ODWALV20

ODWALV30

ODWALV3X

ODWALV40

1,000

1,800

2,200

940

1,000

280

300

350

340

320

<500

<500

<500

<500

<500

2,500

2,500

2,800

2,500

1,800

8,000

8,200

11,000

9,500

10,000

LRWRZZ10

LRWRZZ20

LRWRZZ2X

ODIPLC20

LRIHAZ10

540

460

1,200

1,000

1,300

240

270

250

290

230

<500

<500

<500

<500

<500

2,200

2,100

2,000

2,100

2,100

700

800

800

1,200

400

ODWALV50

ODWRZY10

ODWRZY1X

ODWRZW10

2,000

1,100

1,200

920

280

300

220

310

<500

<500

<500

<500

2,400

2,100

2,200

2,100

5,200 ODICAE10 760

1,600 ODIEMC3X 200

1,500 ODISMC10 1,100

2,300 ODISMC1X 920

250

260

250

280

<500

<500

<500

<500

2,200

2,100

2,100

2,000

2,000

1,300

1,300

1,500
CHEMICAL AND MINERALOGIC ASPECTS OF FRACTIONATED ASH 

BULK OXIDES

[Values in percent. LOI, loss on ignition. Fe£O3 is total Fe calculated as Fe2O3]

19

Sample

LRWSHP10

LRWSHP20

LRWSHP30

LRWSHP40

LRWSHP50

LRWSHP60

LRWSHP70

LRWSHP80

LRWSHP90

LRWSHPOO

ODWRRR10

ODWRRR1X

ODWRRR20

ODWRRR2X

ODWRRR30

ORWRRR40

ORWRRR50

LRWYVZ10

LRWYVZ20

LRWRAZ10

LRWRAZ20

LRWELZ10

LRWYKZ40

I.RWYKZ50

LRWCRZ10

LRWCRZ20

ODWRIS10

LRWMLZ10

LRWMLZ1X

LRWMLZ20

LRWMLZ2X

LRWMLZ30

LRWMLZ40

ODWALV10

ODWALV20

ODWALV30

ODWALV3X

ODWALV40

ODWALV50

LRWCOZ10

LRWCOZ1X

LRWCOZ20

LRWCOZ30

ODWRZY10

ODWRZY1X

ODWRZW10

ODWRZW20

LRWRZZ10

LRWRZZ20

LRWRZZ2X

LRWRLZ10

LRWRLZ20

LRWSGZ10

LRWSGZ20

ORWSPT10

ODWSPK10

ODWSPK20

ODWSPK30

ODIPLC20

LRIHAZ10

ODICAE10

ODIEMC30

ODIEMC3X

ODISMC10

ODISMC1X

ODMMIL10

ODMMIL20

ODMMIL30

ODMMIL40

Latitude

46.20

46.20

46.20

46.20

46.20

46.20

46.20

46.20

46.20

46.20

46.54

46.54

46.54

46.54

46.54

46.54

46.54

46.58

46.58

47.00

47.00

47.00

46.60

46.60

47.00

47.00

46.29

47.13

47.13

47.13

47.13

47.13

47.13

47.71

47.71

47.71

47.71

47.71

47.71

46.66

46.66

46.66

46.66

47.13

47.13

47.13

47.13

47.13

47.13

47.13

46.98

46.98

47.30

47.30

47.66

47.66

47.66

47.66

47.34

47.45

47.68

47.12

47.12

47.31

47.31

46.87

46.87

46.87

46.87

Longitude

122.19

122.19

122.19

122.19

122.19

122.19

122.19

122.19

122.19

122.19

121.96

121.96

121.96

121.96

121.96

121.96

121.96

120.67

120.67

120.67

120.67

120.55

120.50

120.50

120.00

120.00

119.28

119.28

119.28

119.28

119.28

119.28

119.28

118.94

118.94

118.94

118.94

118.94

118.94

118.86

118.86

118.86

118.86

118.38

118.38

118.38

118.38

118.38

118.38

118.38

118.34

118.34

117.97

117.97

117.43

117.43

117.43

117.43

116.89

116.78

116.78

116.60

116.60

116.56

116.56

113.98

113.98

113.98

113.98

Si02

62.8

62.3

62.3

62.9

64.3

63.2

63.8

64.0

59.7

63.2

62.0

61.6

62.0

62.3

63.2

58.4

64.5

59.7

59.0

56.9

63.3

60.5

66.9

66.9

63.8

63.5

60.4

65.7

65.5

65.5

65.4

65.7

65.6

61.4

61.2

61.7

61.4

62.4

64.4

60.1

58.8

64.1

64.7

65.8

66.5

66.7

68.8

66.1

66.8

66.0

65.6

66.1

67.3

66.7

65.9

62.1

66.4

66.5

66.9

66.2

66.4

67.2

67.4

67.0

66.7

63.6

67.7

64.6

64.6

A1 2 0 3

17.4

17.3

17.3

17.5

17.4

17.4

17.4

17.4

17.7

17.5

17.0

17.1

16.8

17.0

16.4

19.7

16.3

18.2

18.1

18.7

16.9

17.9

15.8

15.7

16.7

16.7

17.4

16.2

16.3

16.3

16.1

16.2

16.2

17.3

17.3

16.7

17.1

16.7

16.4

18.7

18.0

16.7

13.3

16.1

16.2

16.2

15.5

16.1

16.4

16.2

16.1

16.3

16.0

16.0

16.7

16.9

16.2

16.5

16.0

15.8

16.1

16.0

16.0

16.0

16.0

16.7

16.0

16.4

16.5

Fe 2 0 3

4.97

4.83

5.10

4.94

4.97

4.99

4.60

4.48

6.28

4.75

5.22

5.27

5.19

5.18

4.74

5.42

4.93

6.16

6.55

7.28

5.47

5.74

3.55

3.88

5.27

5.42

5.96

4.43

4.51

4.45

4.51

4.36

4.37

5.35

5.33

5.05

5.12

5.04

4.38

5.61

7.09

5.21

6.29

4.07

4.09

4.04

3.27

4.14

4.25

4.30

4.34

4.35

3.87

3.83

4.23

4.98

3.94

4.07

3.78

3.65

3.99

3.70

3.71

3.72

3.71

4.52

3.59

4.28

4.22

MgO

2.2

2.2

2.4

2.3

2.2

2.2

2.0

1.9

3.3

2.0

2.3

2.4

2.3

2.2

2.0

2.9

2.1

3.3

3.5

3.9

2.3

2.6

1.3

1.4

2.1

2.1

2.7

1.6

1.6

1.6

1.6

1.5

1.6

2.3

2.3

2.1

2.3

2.1

1.7

2.6

3.1

2.0

1.8

1.5

1.4

1.5

1.1

1.4

1.5

1.5

1.5

1.5

1.3

1.3

1.6

2.1

.4

.5

.3

.2

.5

.3

.3

1.3

1.3

1.9

1.2

1.7

1.6

CaO

5.19

5.17

5.35

5.34

5.15

5.26

5.01

4.97

6.05

5.17

5.33

5.35

5.26

5.23

4.80

7.28

4.43

6.38

6.35

7.07

4.96

5.94

3.74

3.68

4.77

4.86

5.75

4.22

4.27

4.24

4.23

4.15

4.17

5.57

5.62

5.25

5.41

5.22

4.61

6.40

6.33

4.70

3.02

4.08

4.10

4.09

3.29

4.04

4.08

4.15

4.09

4.15

3.91

3.92

4.57

5.27

4.14

it. 21

3.85

3.78

4.09

3.85

3.86

3.92

3.91

4.92

3.80

4.58

4.58

Na 20

4.4

4.4

4.4

4.4

4.4

4.4

4.5

4.5

4.2

4.4

4.3

4.3

4.4

4.4

4.3

4.3

4.5

4.2

4.2

4.1

4.4

4.4

4.5

4.5

4.4

4.4

4.3

4.5

4.5

4.5

4.5

4.5

4.5

4.3

4.3

4.3

4.3

4.4

4.5

4.4

4.2

4.5

2.2

4.5

4.5

4.5

4.6

4.6

4.6

4.5

4.5

4.6

4.6

4.6

4.5

4.4

4.5

4.5

4.6

4.5

4.4

4.7

4.6

4.6

4.6

4.4

4.6

4.5

4.4

K 2 0

1.33

1.32

1.34

.32

.35

.33

.38

.31

.03

.28

1.30

1.31

1.34

1.35

1.47

.78

1.42

.96

.93

.72

1.34

1.15

1.74

1.76

1.42

1.39

1.22

1.59

1.58

1.58

1.58

1.60

1.58

1.28

1.27

1.36

1.32

1.38

1.50

1.03

.99

1.44

2.03

1.62

1.62

1.63

1.84

1.62

1.61

1.59

1.60

1.62

1.69

1.69

1.53

1.36

1.62

1.59

1.69

1.67

1.72

1.70

1.70

1.69

1.67

1.46

1.72

1.55

1.53

Ti02

0.64

.65

.70

.66

.66

.65

.61

.59

.82

.66

.70

.71

.71

.71

.66

.70

.65

.80

.83

.90

.75

.85

.48

.52

.73

.75

.87

.64

.65

.64

.66

.62

.62

.74

.74

.61

.70

.68

.60

.79

1.00

.73

1.07

.58

.58

.58

.45

.60

.61

.62

.62

.63

.56

.55

.59

.68

.56

.58

.54

.53

.58

.53

.53

.54

.53

.66

.52

.61

.61

P 2°5

0.1

.1

.2

.1

.1

.1

.2

.1

.2

.1

.2

.2

.2

.2

.2

.2

.1

.2

.2

.2

.2

.2

.1

.2

.2

.2

.2

.2

.1

.2

.2

.2

.1

.2

.2

.2

.3

.2

.2

.2

.2

.2

.2

.1

.2

.2

.1

.2

.2

.1

.1

.2

.2

.1

.2

.3

.2

.2

.1

.1

.2

.1

.1

.1

.1

.2

.1

.2

.2

MnO

0.07

.07

.07

.07

.07

.07

.06

.06

.10

.06

.07

.07

.07

.07

.06

.08

.07

.09

.10

.11

.08

.08

.05

.06

.07

.07

.08

.06

.06

.06

.06

.06

.06

.07

.08

.07

.07

.07

.06

.08

.09

.07

.11

.05

.06

.06

.05

.06

.06

.06

.06

.06

.05

.05

.05

.07

.05

.06

.05

.05

.05

.05

.05

.05

.05

.06

.05

.06

.06

LOI

0.41

.39

.49

.66

.48

.15

.54

.75

.68

.64

1.04

1.15

1.20

1.26

1.61

.12

.94

.68

.65

.26

.45

.66

1.20

1.89

.66

.65

.71

.71

1.10

.95

.86

.56

.54

1.32

1.20

1.55

1.48

1.46

1.08

.38

.54

.58

4.98

.72

1.00

.68

.92

.76

.70

.52

.75

.50

.65

.64

.91

1.05

.71

1.30

.81

1.82

1.05

.78

.76

.75

.89

1.06

.76

1.06

.99
20 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

BULK CATIONS

[Values in ppm, except those labelled in pet]

Sample

LRWSHP10

LRWSHP20

LRWSHP30

LRWSHP40

LRWSHP50

LRWSHP60

LRWSHP70

LRWSHP80

LRWSHP90

LRWSHPOO

ODWRRR10

ODWRR1X

ODWRRR20

ODWRRR2X

ODWRRR30

ORWRRR40

ORWRRR50

LRWYVZ10

LRWYVZ20

LRWRAZ10

LRWRAZ20

LRWELZ10

LRWYKZ40

LRWYKZ50

LRWCRZ10

LRWCRZ20

ODWRIS10

LRWMLZ10

LRWMLZIX

LRWMLZ20

LRWMLZ2X

LRWMLZ30

LRWMLZ40

ODWALV10

DDWALV20

ODWALV30

ODWALV3X

ODWALV40

ODWALV50

LRWCOZ10

LRWCOZ1X

LRWCOZ20

LRWCOZ30

ODWRZY10

ODWRZY1X

ODWRZW10

ODWRZW20

LRWRZZ10

LRWRZZ20

LRWRZZ2X

LRWRLZ10

LRWRLZ20

LRWSGZ10

LRWSGZ20

OKWSPT10

ODWSPK10

ODWSPK20

ODWSPK30

ODIPLC20

LRIHAZ10

ODICAE10

ODIEMC30

ODIEMC3X

ODISMC10

ODISMC1X

ODMMIL10

ODMMIL20

ODMMIL30

ODMMIL40

Ag

<7.8

<.l

<1.6

<6.2

<3.7

<1.7

<5. 1

<1.9

<5.6

<9.9

3.1

<9.4

<4.2

<9.3

<7.1

<5.6

<.50

<7.4

<7.2

<7.9

<7.3

<6.5

4.9

1.2

<7.9

<8.7

<4.9

<2.8

<5.5

<3.2

<22.1

<.6

<8.6

<7.0

<8.8

<5.7

4.9

<2.4

<7.3

<5.3

<11.2

<3.8

<5.8

<6.2

<6.3

<5.5

<6.7

<5.0

<6.2

<1.6

<7.6

<6.5

1.1

<1.7

1.0

0

<1.3

<6.8

<3.5

<2.8

.9

<4.4

<1.1

<10.9

<7.2

<4.8

<3.4

1.4

<.9

Al 

pet

10.1

9.9

9.9

9.9

9.7

9.7

9.9

9.5

9.9

10.0

9.7

9.5

10.2

9.7

9.3

11.3

9.4

10.4

10.1

10.5

9.5

10.0

8.9

9.0

9.3

9.4

9.9

8.2

9.2

9.2

9.1

9.2

9.5

10.0

9.8

9.7

9.9

10.0

9.6

10.4

10.4

9.5

7.2

9.0

9.7

9.2

8.8

9.2

9.2

9.5

9.3

9.1

7.8

9.1

9.3

9.7

9.6

9.1

8.9

8.7

9.9

9.1

9.3

9.1

9.0

9.9

8.8

9.4

9.0

Au

5.2

3.0

5.1

3.9

4.2

3.4

4.8

4.4

5.6

4.7

3.5

2.9

5.0

5.6

4.4

5.5

3.7

5.0

5.5

5.4

4.6

4.8

2.1

3.7

3.5

3.7

4.5

3.4

4.5

3.6

2.3

3.8

2.6

4.4

4.1

3.4

5.4

5.0

4.2

4.8

5.5

5.2

4.4

2.1

3.7

3.5

2.2

3.5

2.6

4.0

2.8

3.5

2.9

3.5

2.7

6.0

1.3

5.1

1.5

3.1

5.1

2.1

4.0

2.9

3.4

3.5

4.0

3.9

3.0

B

<11.1

<13.8

<3.9

<13.2

<13.2

18.8

1.1

17.1

<19.7

<1.0

91.5

44.8

2.6

<8.6

.7

<13.4

7.6

<4.7

<6.3

269.8

10.9

7.2

<11.5

10.6

<12.3

<14.9

<11.1

<14.0

<10.2

<16.2

3.5

<15.5

6.6

64.3

7.3

39.5

18.6

3.6

<8.7

6.9

101.8

<.l

<16.8

<3.6

<7.6

<.7

<2.3

4.1

<17.5

<13.4

<12.3

<14.9

<13.2

<14.4

<6.9

.1

21.9

<12.7

<7.5

<9.7

<10.8

<8.8

<12.3

<14.5

<11.9

.8

<3.6

13.8

<11.1

Ba

310

310

310

310

310

300

320

290

250

290

320

310

340

320

350

220

550

250

240

320

310

400

410

410

320

320

300

330

360

360

370

370

380

320

310

340

330

350

370

260

360

340

660

360

390

380

410

370

360

380

370

360

330

380

350

330

390

360

370

370

870

390

400

390

380

360

380

360

350

Be

0.85

.87

.86

.89

.88

.85

.85

.80

.72

.84

.89

.92

.95

.85

.94

.62

.86

.66

.65

.50

.85

.82

1.10

1.08

.80

.73

.75

.78

.93

.91

.92

.99

.97

.90

.84

.90

.96

1.02

.99

.74

.69

.92

1.15

.95

1.01

1.02

1.11

1.02

.96

.99

.95

.90

.86

1.03

.96

.94

.98

1.03

1.03

.98

1.28

1.04

1.09

1.01

.98

1.00

1.01

.98

.93

Ca

3.4

<3.4

3.4

3.4

3.3

3.3

3.3

3.2

4.0

3.4

3.4

3.4

3.6

3.4

3.2

4.9

3.0

4.3

4.2

4.6

3.3

3.8

2.6

2.6

3.2

3.2

3.8

2.6

2.9

2.9

2.8

2.8

2.9

3.8

3.6

3.4

3.6

3.6

3.2

4.2

4.3

3.2

2.0

2.8

2.9

2.8

2.3

2.7

2.8

2.9

2.8

2.8

2.3

2.7

3.0

3.4

2.9

2.8

2.6

2.5

3.0

2.6

2.7

2.7

2.6

3.3

2.5

3.1

3.0

ca

<0.32

.14

<.26

<.29

.06

<.08

<.40

<.30

<.26

<.01

<.15

<.34

<.26

<. 18

<.37

<.35

.11

<.30

<.27

<.50

<.02

<.06

<. 20

.31

<.31

<.14

<.25

<.47

<. 14

<.18

<.79

<.34

.01

<.21

<.28

<.02

.18

.06

<.26

<.35

<.41

.14

<.02

<.48

<.32

<.ll

.07

<.29

<.06

<.24

<.39

<.03

<.47

<.07

<.23

<.24

.01

<.24

<. 11

<.19

.16

.06

<.25

<.45

<.31

<.02

<.22

<. 14

<.10

Ce

14

14

15

12

16

13

14

11

13

12

15

13

17

16

18

8

15

12

11

6

15

13

16

18

14

14

13

15

18

15

15

16

15

17

14

15

18

19

18

9

11

16

43

14

16

16

16

15

15

16

16

15

15

16

16

18

14

16

14

16

25

15

18

14

15

17

19

18

17

Co

13

14

14

13

13

13

12

11

19

13

15

14

15

14

12

16

13

19

20

21

14

15

8

9

14

14

16

10

10

10

10

10

11

14

14

14

15

14

11

15

20

14

16

9

10

10

7

10

10

10

10

10

8

8

10

13

9

9

8

8

10

8

9

8

8

12

8

11

11

Cr

10

14

17

14

10

6

4

7

37

8

12

17

12

17

16

21

8

19

20

16

12

24

10

11

12

14

45

8

10

9

10

12

9

21

18

21

21

17

13

18

18

14

41

9

9

9

6

12

21

10

12

10

7

10

11

23

9

9

7

7

12

8

9

9

9

21

8

17

15

Cu

40

43

41

39

39

41

39

31

35

37

46

47

52

47

49

35

42

44

45

40

49

38

54

57

43

45

48

40

48

48

48

45

49

46

46

50

48

53

48

37

48

46

26

46

49

47

45

45

45

45

45

48

40

45

43

49

47

45

45

42

49

45

46

45

42

51

44

48

42

Dy

9

11

11

10

9

11

9

9

12

8

11

8

11

11

9

10

10

11

11

12

12

12

9

12

11

9

11

8

11

8

2

10

9

9

9

10

15

12

8

10

12

12

15

7

9

9

7

10

7

10

8

9

7

10

9

13

9

8

8

9

11

9

10

7

7

10

8

9

8

Er Eu

0.3 <0.5

1.1 <.l

1.2 <1.0

1.0 .2

.7 <.5

.3 <.6

.6 <.8

1.5 <1.1

1.2 <1.9

.4 <.9

.4 <.4

<.4 <.8

1.0 <1.1

.9 <.6

.7 <.7

<.2 <3.0

1.0 <1.5

0 <2.2

.3 <2.7

.2 <3.0

.7 <1.0

1.0 <1.1

1.1 <.7

1.9 <.3

.6 <.9

<.3 <1.6

.4 <1.4

.1 <1.8

1.9 <.7

.7 <.7

<3.3 <3.6

1.4 <.7

.2 <.3

.6 <1.8

<0 <1.1

.5 <1.1

2.4 <.l

1.4 <.4

.4 <.7

.3 <1.9

<.3 <2.4

1.5 <.7

3.0 .8

. 1 <.8

.2 <1.1

.7 <1.2

<. 1 <.6

1.5 <.5

<. 2 <.7

1.2 <.2

.3 <.9

.4 <.7

1.2 <1.0

2.0 <.5

.9 <.9

1.8 <1.5

.9 <.4

.3 <.7

.8 <1.1

.7 <.4

1.8 .6

.7 <.8

1.5 <.4

<1.0 <1.2

1.0 <.4

1.1 <.2

.7 <.8

1.7 <.7

.9 <1.1

Fe 

pet

3.7

3.7

3.6

3.6

3.6

3.5

3.4

3.3

4.5

3.5

3.7

3.7

4.1

3.8

3.4

4.1

3.5

4.6

4.7

5.1

3.8

4.0

2.7

2.9

3.7

3.8

4.3

3.0

3.3

3.3

3.3

3.2

3.4

4.0

3.9

3.7

3.8

3.8

3.4

4.0

5.2

3.7

4.2

3.0

3.2

3.0

2.5

3.0

3.1

3.3

3.2

3.2

2.6

2.9

3.1

3.7

3.1

3.0

2.7

2.6

3.3

2.8

2.9

2.8

2.8

3.4

2.7

3.2

3.1

Ga

23

22

23

20

24

22

24

25

26

23

23

19

24

21

25

24

22

22

25

25

23

23

21

19

23

19

23

18

24

22

20

24

20

27

20

21

26

25

25

22

25

24

18

18

23

20

18

22

20

22

19

23

19

19

22

26

16

19

20

20

28

19

24

20

21

23

23

21

23

Ge

30

27

30

27

29

25

27

26

41

26

30

26

31

31

22

36

26

38

41

44

31

30

17

17

27

23

30

18

19

21

18

22

19

31

25

26

34

30

23

33

35

28

21

18

20

19

15

17

16

21

18

19

13

19

19

28

16

18

13

18

24

17

17

17

16

25

18

24

20

Hf

<11

<1

<8

<7

<4

<3

<4

<3

<13

<9

<6

<8

<3

<11

<3

<4

<6

<12

<9

<10

<7

<5

<4

<5

<8

<7

<8

<7

<9

<6

<23

<6

<1

<6

<8

<3

5

<4

<9

<8

<8

0

<4

<7

<6

<4

<4

<3

<2

<5

<11

<9

<2

<4

<1

<5

<5

<4

<3

<6

<2

<4

<1

<8

<3

<4

<5

<7

<2

Ho

1.3

.6

1.1

.7

1.0

.7

.7

.8

1.0

1.1

1.1

.5

.7

.6

1.2

.3

1.1

.8

1.3

.6

1.3

.9

.4

.7

1.2

.3

.9

.8

1.3

.6

.3

.7

.8

.8

.3

.5

.9

1.5

1.2

.2

1.5

1.3

1.3

.3

.7

.2

.3

.2

.5

.5

.7

.5

.8

.6

.5

1.3

<. 1

.7

.2

.7

1.6

<.l

1.0

.4

.7

1.3

1.3

1.2

1.0

In

<5

8

17

2

2

7

16

3

7

<9

<!

<13

10

<7

8

<13

9

2

9

<7

5

3

5

7

<2

<13

<8

10

2

<11

<55

3

<11

<5

<6

<4

24

21

<5

6

10

21

17

<9

<10

<9

<27

3

<17

4

<13

<5

11

15

<5

8

<9

2

<15

<5

13

<6

4

<20

<5

<5

5

11

11

K 

pet

1.1

1.2

1.2

1.2

1.2

1.1

1.2

1.1

.8

1.1

1.1

1.2

1.3

1.2

1.3

.7

1.2

.8

.8

.6

1.2

1.1

1.7

1.7

1.2

1.2

1.1

1.1

1.4

1.4

1.4

1.5

1.5

1.1

1.0

1.2

1.3

1.2

1.3

.9

.8

1.3

1.8

1.5

1.5

1.6

1.7

1.5

1.5

1.5

1.5

1.4

1.2

1.5

1.3

1.3

1.5

1.4

1.5

1.5

1.6

1.6

1.5

1.6

1.5

1.3

1.4

1.3

1.2

La 

pet

16

19

16

18

17

15

15

14

14

14

17

16

18

17

19

12

15

14

14

12

16

15

18

19

16

16

15

15

18

18

17

19

17

17

16

18

19

19

19

13

15

17

40

17

18

18

21

18

18

19

17

18

16

18

17

18

18

17

17

18

24

20

19

18

18

19

18

19

17

Li

21

23

21

21

22

22

22

23

18

23

23

22

26

24

25

16

26

17

18

15

24

20

28

29

25

24

22

24

26

27

27

27

28

23

22

24

23

26

29

19

19

25

26

27

29

29

31

29

27

29

27

27

24

28

24

24

29

27

28

27

34

29

30

28

29

25

30

26

25

Mg Mn 

pet

1.2 690

1.2 710

1.3 710

1.2 690

1.2 690

1.2 670

1.1 650

1.0 610

1.6 890

1.1 640

1.2 710

1.2 710

1.3 760

1.2 720

1.0 630

1.5 750

1.1 690

1.7 930

1.7 940

1.9 990

1.2 740

1.3 760

.7 520

.8 580

1.1 690

1.1 700

1.4 780

.8 550

.9 600

.9 600

.9 590

.9 600

.9 610

1.3 730

1.2 720

1.1 680

1.2 720

1.2 700

1.0 620

1.4 730

1.6 900

1.1 680

1.0 1,010

.8 570

.8 610

.8 570

.6 510

.8 570

.8 570

.9 600

.9 590

.9 590

.6 480

.7 550

.9 560

1.1 670

.8 580

.8 560

.7 530

.7 510

.9 610

.7 530

.7 550

.7 540

.7 540

1.1 630

.7 510

.9 590

.9 550
CHEMICAL AND MINERALOGIC ASPECTS OF FRACTIONATED ASH 21 

BULK CATIONS-Continued

[Values in ppm, except those labelled in pet]

Mo

0.2

.9

<.4

<.2

.5

<.3

.7

.8

<.3

.9

.2

.1

.6

.9

1.1

.6

<.9

<.2

.1

<.6

<.4

.2

1.0

1.0

.7

<.2

.6

<.3

.9

.7

.3

1.0

.4

.3

<.2

.04

1.9

1.1

.8

<.3

<.8

1.4

<.2

.4

.9

.2

.4

.5

.6

1.2

.2

.2

.4

.1

.2

<.03

.4

.7

1.0

.5

2.0

.5

1.3

1.0

.4

.6

.7

.2

.1

Na 

pet

3.7

3.7

3.6

3.6

3.6

3.6

3.7

3.6

3.5

3.7

3.6

3.5

3.8

3.6

3.6

3.6

3.7

3.5

3.4

3.4

3.6

3.5

3.7

3.7

3.6

3.6

3.6

3.3

3.7

3.7

3.6

3.7

3.9

3.7

3.6

3.6

3.7

3.8

3.8

3.6

3.6

3.7

1.9

3.7

4.0

3.8

3.8

3.7

3.7

3.9

3.7

3.7

3.2

3.7

3.6

3.6

3.9

3.7

3.7

3.6

3.9

3.8

3.9

3.8

3.8

3.8

3.7

3.7

3.5

Nb

3.7

4.0

5.2

4.8

4.5

3.6

4.5

3.8

5.1

4.3

3.8

4.7

6.0

5.3

5.4

4.7

3.3

4.8

4.9

4.5

3.7

5.3

3.8

3.9

4.5

4.2

6.4

3.5

3.9

4.2

3.6

4.6

4.5

5.8

4.9

6.3

5.9

6.2

5.4

4.3

5.3

5.2

5.2

3.6

4.7

3.7

3.6

3.5

4.0

5.2

4.0

4.2

3.5

3.6

3.3

4.5

4.4

4.2

3.9

4.7

5.2

3.1

4.4

4.1

4.0

5.8

3.7

5.3

4.3

Nd

9.1

6.8

10.1

5.5

6.8

6.2

8.7

7.0

5.8

2.8

6.7

5.9

13.6

5.9

11.6

1.7

8.0

2.7

4.9

<3.4

8.0

10.2

11.0

14.8

6.0

5.3

7.7

7.0

11.0

10.1

1.3

12.5

8.6

7.1

8.4

8.0

14.8

10.8

10.7

1.9

2.2

10.4

32.1

4.4

8.5

12.3

6.0

7.8

8.7

14.5

8.0

8.1

7.7

11.6

10.9

15.3

8.4

10.4

10.5

9.6

19.4

10.0

12.9

10.7

12.2

13.9

9.7

14.2

11.6

Ni

11

13

16

13

12

11

8

8

21

10

18

17

19

17

15

22

9

19

21

20

13

20

10

12

13

13

32

9

10

9

7

10

9

21

19

19

20

20

12

17

21

14

19

9

10

10

7

9

9

10

10

10

7

8

11

17

11

10

7

7

10

8

9

6

8

19

8

16

14

P 

pet

0.067

.068

.071

.067

.068

.065

.062

.059

.071

.061

.083

.081

.089

.083

.088

.062

.064

.078

.079

.076

.076

.078

.072

.079

.074

.074

.081

.064

.071

.071

.068

.070

.074

.087

.084

.091

.089

.095

.081

.073

.084

.074

.087

.069

.073

.070

.064

.068

.068

.073

.070

.069

.062

.070

.073

.085

.076

.072

.065

.066

.078

.068

.070

.067

.068

.085

.065

.080

.075

Pb

7.6

7.1

5.0

8.2

7.2

7.2

9.5

8.3

5.6

7.2

5.6

6.4

4.5

<.8

13.2

7.1

17.0

6.1

6.2

5.0

9.6

7.9

21.1

47.3

7.4

4.9

7.9

4.9

11.9

5.5

6.9

10.5

8.5

7.2

5.8

6.3

12.3

11.7

10.8

5.9

5.2

10.7

14.7

7.3

8.4

7.9

9.8

8.5

7.7

9.7

6.2

5.6

4.7

9.8

13.4

10.6

8.0

6.7

6.9

8.1

31.3

9.4

9.2

9.5

9.2

9.7

9.8

12.5

8.7

Pr

0.7

<1.9

1.1

<0

<.5

1.2

.9

2.5

1.2

<.7

2.3

<3.5

<.7

4.0

<.5

.2

2.3

<2.4

<0

<3.6

2.6

.4

<1.5

3.9

<.6

<4.3

<1.5

<1.1

.6

<.8

<8.5

1.9

<.5

<2.2

<5.2

<3.1

5.0

3.1

<.l

<3.6

<4.7

3.5

2.2

<2.3

<1.5

<2.2

<2.9

.8

<.7

.4

<3.3

<1.1

1.2

.3

<-8

4.3

<4.2

<.4

<.8

<1.5

5.3

<1.4

2.7

<3.3

<2.9

1.0

<.5

.8

1.6

Rh

4.0

4.0

4.0

4.0

4.0

3.9

4.0

3.9

3.9

4.0

4.0

3.9

4.3

5.1

4.0

4.0

4.0

3.9

3.9

3.8

4.0

4.0

4.0

3.9

4.0

4.0

4.0

3.6

4.0

4.0

3.8

4.1

4.2

4.1

4.0

4.0

4.1

4.2

4.1

4.0

4.1

4.1

2.4

4.0

4.3

4.1

4.0

4.1

4.0

4.2

4.1

4.0

3.5

4.1

3.9

4.0

4.2

4.0

4.0

3.9

4.3

4.1

4.3

4.0

4.1

4.2

4.0

4.1

3.9

Sb

6.0

6.3

4.9

5.6

5.9

5.1

<.8

5.9

5.1

3.9

3.8

.0

6.6

11

5.8

3.1

6.3

3.6

2.7

<.8

8.4

1.1

4.4

10.5

2.3

.4

7.5

1.5

5.4

4.0

<3.7

5.6

3.5

4.9

.4

2.5

12.4

3.6

3.4

3.0

1.7

5.9

6.9

2.6

4.5

2.4

1.5

6.2

.7

8.8

4.7

<.3

2.3

3.6

5.5

3.6

9.3

3.4

2.1

<.3

9.0

<.2

4.9

3.6

2.5

7.9

6.5

5.0

5.3

Sc

10

11

11

11

11

11

10

9

14

11

11

11

12

11

10

13

10

14

14

16

11

12

8

9

10

11

12

8

9

9

9

9

9

12

11

10

11

11

9

12

14

11

15

8

9

8

7

8

9

9

9

9

7

8

9

11

9

9

7

8

10

a

8

8

8

10

8

10

9

Se

13

11

3

8

13

6

13

10

15

17

16

5

8

11

8

13

<2

9

8

11

14

2

11

2

17

2

5

1

4

11

9

11

3

6

12

4

13

12

7

12

8

14

2

10

12

9

9

10

11

13

3

11

3

2

12

12

8

9

9

8

13

0

6

7

4

12

4

12

13

Sm

0.2

2.7

2.1

1.0

2.4

2.2

1.0

1.3

1.0

<.l

1.1

.1

3.1

1.1

2.3

<. 2

2.4

.5

<.2

<1.1

2.8

.5

3.2

5.4

.7

2.1

1.8

2.1

3.0

.1

<4.7

2.8

2.2

.1

.8

2.0

6.4

2.3

<.8

1.3

<.6

3.6

7.0

.5

3.4

2.4

2.3

3.4

.9

1.9

.1

.9

2.2

3.7

1.7

6.3

2.3

2.5

2.5

1.7

4.0

2.4

3.6

<1.3

<.l

2.2

1.5

2.3

3.1

Sn

0.3

.3

<.l

<2.0

.9

<1.3

1.4

3.0

14.7

1.3

<4.2

.3

<1.5

<.5

<1.3

<.7

<.9

<.6

<1.2

<.7

.9

<2.7

<.6

1.4

<-7

<1.5

1.7

<1.4

<.4

1.4

.7

1.7

.4

1.4

<1.7

<.4

3.5

.5

<.7

<2.0

<1.8

.2

.1

.3

<2.1

<1.6

<1.7

<2.0

2.7

.1

<2.7

.2

<1.0

<.l

.5

1.1

.2

.1

.2

2.4

4.9

<.6

<1.3

<.l

1.9

3.6

1.0

0

.6

Sr

510

510

510

510

490

490

490

470

550

490

490

490

520

500

440

680

430

600

580

630

470

550

370

360

450

460

520

370

410

410

400

410

420

530

520

490

510

500

450

590

590

450

320

400

420

400

340

400

400

420

410

400

330

390

430

490

420

410

370

360

430

380

390

390

380

470

360

430

420

Tb

2.0

7.4

6.5

4.7

7.9

5.4

3.8

5.0

7.6

1.2

8.2

4.7

5.4

5.0

4.1

3.5

7.6

6.5

6.5

2.8

11.0

7.5

4.1

4.1

7.2

9.1

8.1

6.4

8.7

2.8

<3.9

5.0

6.8

5.8

8.0

7.3

12.3

9.3

9.3

9.6

2.8

10.8

12.6

8.1

5.8

<.5

6.0

7.6

2.4

9.0

<1.5

6.8

4.6

3.7

6.3

8.5

.6

8.2

6.4

6.3

7.0

4.4

9.0

.5

3.2

9.6

1.8

7.6

7.7

Th

<3.3

<2.7

<.6

<4.4

<2.1

<1.5

<2.4

<0

<2.4

<1.9

<2.5

<3.9

<2.1

<3.2

<1.5

<4.0

<.5

<3.5

<2.3

<3.3

<1.3

<2.4

<1.7

2.7

<.l

<3.4

<2.7

<1.3

.7

<2.3

<9.8

.0

<1.3

<2.3

<4.1

<3.7

.0

<1.3

<.5

<3.8

<3.7

1.2

8.3

<1.8

<1.2

<1.8

<3.1

<1.4

<3.3

<1.4

<3.7

<2.3

<.4

1.4

<1.9

1.0

<4.8

<2.6

<1.9

<.l

1.7

<2.8

1.1

<4.1

<3.4

<2.8

<.8

<1.9

.2

Ti

0.41

.42

.43

.42

.41

.39

.37

.35

.50

.40

.43

.43

.48

.45

.39

.44

.35

.50

.52

.52

.45

.51

.30

.31

.45

.45

.52

.36

.38

.40

.38

.38

.40

.47

.46

.43

.45

.45

.39

.47

.64

.45

.59

.36

.38

.36

.28

.36

.36

.40

.39

.38

.31

.34

.30

.43

.36

.34

.32

.31

.36

.32

.34

.33

.33

.42

.31

.39

.35

Tm

2.2

2.7

2.4

1.9

2.2

2.8

1.9

2.2

1.7

1.4

2.3

1.8

3.3

2.6

2.6

1.8

2.4

1.5

1.3

.8

2.4

2.7

3.0

3.6

2.3

2.8

2.8

3.0

2.9

3.0

1.3

3.2

3.2

2.5

2.7

3.0

3.4

2.9

2.7

1.7

1.8

2.6

5.0

2.7

3.1

3.2

3.2

3.0

2.6

3.0

2.8

3.3

2.9

3.4

3.1

3.3

4.1

2.8

2.7

3.0

3.5

2.9

3.3

2.9

3.2

3.2

2.9

3.0

3.1

U

8.6

<8.2

7.2

<. 3

<1.4

<1.5

23.8

23.7

10.3

6.7

<3.6

<7.6

<5.6

<8.3

7.5

<.l

15.7

<5.6

13.0

<13.4

13.9

<8.3

<7.9

8.3

7.4

<14.3

<3.2

<4.2

24.8

<3.8

<13.5

12.6

<5.8

1.7

<16.3

<11.6

16.2

21.5

10.8

<20.9

<.4

9.8

<9.1

<4.5

7.4

<8.1

<9.5

6.2

4.3

5.9

<12.8

<2.5

5.0

9.9

<5.0

26.9

<28.4

<9.3

<4.7

4.2

37.2

<11.3

4.8

2.0

<4.1

10.9

19.9

13.8

5.0

V W

88 5.0

89 .2

89 <5.9

89 <3.1

87 2.6

84 <7.7

80 <4.0

75 1.8

111 <3.0

86 <3.4

87 <3.2

87 <4.5

96 <4.5

90 <1.8

74 <6.4

98 3.5

77 <7.7

113 .1

116 <5.6

133 <10.3

100 .6

100 <5.3

48 <3.7

53 1.2

100 <5.3

100 <8.0

107 <3.0

71 <10.1

75 3.7

77 2.7

72 <16.1

72 6.1

77 4.6

91 <6.6

90 <8.0

84 <1.2

88 3.3

86 1.9

70 <2.5

107 4.5

154 <8.5

96 9.5

128 <.2

65 <1.7

69 2.8

63 <1.2

38 <6.5

67 <5.0

69 <3.0

76 2.7

75 <8.7

73 2.6

54 <10.5

59 4.7

57 <2.8

82 <7.9

62 .1

59 <6.3

52 1.1

51 8.2

65 8.5

53 <3.5

55 7.6

54 <3.8

55 3.8

76 <6.4

51 <5.6

67 <1.3

63 <1.0

Y

17

16

17

16

17

16

16

14

17

16

18

18

20

19

18

14

15

16

17

16

17

18

17

18

17

17

19

16

17

18

17

17

18

19

18

19

19

20

19

16

20

18

29

17

18

17

17

17

17

18

17

17

15

17

16

19

18

17

16

16

19

17

18

17

16

19

17

18

17

Yb

1.4

1.4

1.4

1.3

1.3

1.4

1.3

1.2

1.3

1.2

1.4

1.4

1.6

1.5

1.3

1.2

1.4

1.4

1.2

1.2

1.5

1.6

1.5

1.5

1.3

1.4

1.4

1.2

1.3

1.3

1.0

1.4

1.5

1.5

1.4

1.4

1.6

1.7

1.3

1.4

1.6

1.4

2.5

1.4

1.4

1.6

1.4

1.5

1.3

1.3

1.2

1.1

1.1

1.3

1.5

1.6

1.5

1.5

1.4

1.3

1.8

1.5

1.5

1.3

1.4

1.6

1.4

1.5

1.3

Zn

76

76

74

74

75

74

71

68

86

69

75

75

85

79

75

73

75

88

101

93

83

80

76

98

79

82

90

65

70

71

69

73

72

78

77

73

76

76

70

76

95

78

97

68

78

67

62

69

69

72

71

72

58

68

66

76

68

64

65

63

77

64

67

65

65

70

62

67

65

Zr

110

110

120

110

110

110

120

120

100

120

120

120

130

120

130

70

130

90

90

70

130

110

150

160

130

120

120

130

140

140

140

150

150

120

120

120

120

130

140

100

100

130

110

150

160

150

170

150

150

150

150

140

130

150

120

120

160

140

150

150

150

150

160

160

150

150

150

150

140
22 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

APPENDIX B. ESTIMATE OF ANALYTICAL ERROR IN CHEMICAL CONCENTRATION DATA FOR

WHOLE ASH

Analytical precision is estimated by the geometric error for each chemical species determined. The geometric error is the antilog of the 

log standard error, and is calculated from the logarithms of the differences in measured concentrations between samples that are members 

of pairs of analytical replicates (splits). The use of logarithmic data minimizes the perturbing effect of uncommon, extreme-value data upon 

the final value of the error parameter. The number of sample pairs from whose data the error parameter calculation was made are also listed 

in the appendix.

Geometric error was calculated from concentration values of 10 pairs of samples. For samples with qualified values (below detection limit, 

where only an upper limit is given), a value of 0.7 times the detection limit was substituted and used in the calculation. The number of pairs 

free of qualified values is given in the table.

WHOLE-ASH CHEMICAL ANALYSES

[LOI, loss on ignition. Fe Og is total Fe calculated as F«2O3]

Chemical Geometric Number of 

species error pairs

Chemical Geometric Number of 

species error pairs

Chemical Geometric Number of 

species error pairs

X-ray fluorescence

S102 

A120 3

Fe 2°3 

MgO

CaO 

Na20 

K20 

TlOo

P2°5 

MnO

LOI

Ion chromatography

1.01

1.01

1.05

1.05

1.01

1.01

1.01

1.05

1.33

1.05

1.18

10

10

10

10

10

10

10

10

10

10

10

Cl" 

F~

1.60

1.08

1.03

1.23

Inductively coupled plasma

spectroscopy

Al

Au

B

Ba

Be

Ca

Ce

Co

Cr

Cu

Dy

Er

Fe

Ga

Ge

Ho

In

K

La

LI

Mg

Mn

Mo

1.04

1.32

2.12

1.08

1.06

1.04

1.11

1.08

1.22

1.08

1.41

2.60

1.07

1.14

1.11

2.50

2.75

1.07

1.06

1.04

1.05

1.06

2.96

10

10

3

10

10

10

10

10

10

10

10

5

10

10

10

9

2

10

10

10

10

10

8

ICP Continued

Na

Nb

Nd

Nl

P

Pb

Rh

Sb

Sc

Se

1.03

1.16

1.76

1.12

1.05

1.30

1.04

4.70

1.06

2.17

10

10

10

10

10

10

10

8

10

10

Sm

Sn

Sr

Tb

Tl

3.55

4.25

1.04

1.88

1.08

7

2

10

9

10

Tm

U

V

Y

Yb

Zn 

Zr

1.24

2.98

1.10

1.06

1.08

1.07

1.04

10

1

10

10

10

10

10
Leachate Chemistry of Ash from the 

May 18, 1980 Eruption of 

Mount St. Helens

By TODD K. HINKLEY and KATHLEEN S. SMITH

With a section on LABORATORY METHODS DEVELOPED FOR 

MOUNT ST. HELENS WATER AND ACID LEACHING STUDIES

By STEPHEN A. WILSON and CAROL A. GENT

CHEMISTRY OF ASH AND LEACHATES FROM THE MAY 18, 1980 

ERUPTION OF MOUNT ST. HELENS, WASHINGTON

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1397-B

CONTENTS

Page

Abstract ............................................. 27

Introduction ......................................... 27

Acknowledgments ..................................... 28

Sample collection and treatment ......................... 28

Laboratory methods developed for Mount St. Helens water and 

acid leaching studies, by Wilson, S. A., and Gent, C. A. . . . 29

Introduction ...................................... 29

Experimental procedures ........................... 29

Leaching studies ............................... 29

Ion chromatographic conditions ............... 29

Inductively coupled plasma-atomic emission spectroscopy conditions ........................ 30

pH studies .................................... 30

Accuracy and precision ............................. 30

Discussion and results .............................. 30

Summary ......................................... 32

Background and literature discussion .................... 32

Results and discussion ................................. 34

Amounts of material removed by water and acid leaching 

treatments ...................................... 34

Possible sources, nature, and solubility of material removed 

by leaching treatments ........................... 36

Species readily removed by deionized water leaching 

treatments and by rain ........................ 37

Amount of material removed using differing amounts of 

leaching solution relative to the amount of ash .... 40

Electrical ion balance in the leachate solutions ...... 40

Results and discussion Continued

Significant correlations between cations and anions in 

the leachate ................................. 44

Ca/Sr ratios in solutes .......................... 46

Amounts of species yielded to mild and harsh leaching 

treatments .................................. 46

Contribution to solute by primary igneous grains ....... 47

Variation in amount of the soluble material ............ 47

Other evidence on source material for acid leach solute 49 

Trends in groups of ash samples ..................... 50

Systematic and random changes in leachate concentrations in the Almira, Wash., time-sequence samples 50 

Differing amounts of material yielded to leaching solutions by groups of ash samples ................. 50

Grain size of the ash ............................... 51

Relationship of leachates of Mount St. Helens ash to 

leachates of common soils ......................... 52

Comparison of amounts of elements removed from ash 

and amounts removed from common soils, and the 

intensity and capacity properties of the two materials 52 

Contrasts in leachable chemistry of ash and typical soils 53 

Conclusions .......................................... 53

References cited ...................................... 54

Appendix C. Complete tabulation of analytical results for 

leachates ........................................... 58

Appendix D. Estimate of analytical error in chemical concentration data for leachates ............................. 64

ILLUSTRATIONS

FIGURES 6-11.

6.

7.

8.

9.

10.

11.

Charts showing:

Effect of acid concentration on the extraction of F", Cl", and PO^3 from the ash using deionized water and 0.01 and

0.1 M H2SO4 and a 1-hour extraction time

Page

30

Effect of leach time on the extraction of F~, Cl", and SO^2 from the ash using deionized water ............... 31

Effect of leach time on the extraction of F~, Cl", and PO"3 from the ash using 0.01 M H2SO4 ................ 31

Ordered plots of ratios (amount of element removed by acid leach -=- amount of element removed by water leach) for

two suites of ash samples not affected by rain on the ground ........................................ 36

Water leach concentrations of solute species in samples collected through five abutting time increments at Almira,

Wash ....................................................................................... 51

Acid leach concentrations of solute species in samples collected through five abutting time increments at Almira,

Wash ....................................................................................... 51

25
26 CONTENTS

TABLES

TABLE 9. Concentration of anions extracted from the ash using deionized water and 0.01 M H28O4 leaching solutions and a 4-hour

extraction time ...................................................................................... 31

10. Concentration of anions extracted from the ash using deionized water, 0.01 M H28O4 , and 0.02 M HNO3 leaching solutions and a 4-hour extraction time ......................................:.............................. 31

11. Changes in pH observed during ash extraction using deionized water leaching solution and 1-, 4-, and 20-hour extraction

times .............................................................................................. 32

12. Average amounts of components removed from the ash by water and acid leaching solutions ................... 35

13. Ranking of abundance of chemical species removed from the ash by water and acid leaches, as percent of total whole-ash

content ............................................................................................ 36

14. Daily rainfall at ash collection sites in Washington State during the time interval between deposition and collection of

some ash samples ................................................................................... 37

15. Effect of rain on amounts of anions removed from the ash by water and acid leaches .......................... 38

16. Effect of rain on amounts of cations removed from the ash by water and acid leaches .......................... 39

17. Comparison of amounts of elements removed from the ash by large and small volumes of water, and from common soils

by the saturated paste method ........................................................................ 41

18. Electrical balances of cation and anion equivalents in deionized water leach solutes and in material apparently removed

from the ash by rain ................................................................................. 42

19. Electrical balances of anion and cation equivalents in deionized water leach solutes from selected ash samples ..... 42

20. Electrical balances of anion, cation, and proton equivalents in 0.01 F H2SO4 acid leach solutes from selected ash samples 43

21. Correlation matrix for species measured in water leach treatment ........................................... 44

22. Correlation matrix for species measured in acid leach treatment ............................................ 45

23. Ca/Sr ratios in solutes, and total amounts of ash removed by leach treatments ................................ 46

24. Correlations between whole-ash calcium, sodium, and silicon, and species removed by water and acid leach treatments 48

25. Correlations between removal by water or acid leach treatments and whole-ash content for each chemical species .. 49

26. Successive pore-volume water leaches of ash compared to water extracts of common soils ...................... 52
CHEMISTRY OF ASH AND LEACHATES FROM THE MAY 18, 1980 ERUPTION OF

MOUNT ST. HELENS, WASHINGTON

LEACHATE CHEMISTRY OF ASH FROM THE MAY 18, 1980 ERUPTION OF

MOUNT ST. HELENS

By TODD K. HINKLEY and KATHLEEN S. SMITH

ABSTRACT

We present and interpret a large body of chemical leachate data from 

a large number of ash samples from the May 18, 1980 eruption of 

Mount St. Helens, Wash. The postdepositional history and circumstances of collection and storage of the samples are well documented. 

We performed leach treatments on 39 ash samples with both nearneutral (deionized water) and low-pH (0.01 F H2SO4) solutions, using 

a 4-hour leaching time with a 14:1 solution-to-ash ratio; deionized water 

and acid leach treatments were done on separate sample aliquots rather 

than in sequence on the same aliquots. The near-neutral treatments 

may approximate natural conditions of exposure to rain, soil solutions, 

and ground water, and the low-pH treatments may approximate exposure to the very thin zones of soil solution surrounding plant roots. 

The purpose of the treatments was to gain information on the amounts, 

compositions, and removal sequences of materials on and within the 

grains of tephra, and to gain insights into the processes of formation 

of the tephra grains as they emerged from the volcano and were 

transported through the air.

The deionized water leach treatment removed material as follows. 

Of the metals, Ca, Na, Mg, K, Si, Mn, Ba, and Sr were removed in 

greatest absolute amounts, but Ni, Co, Mn, and Ca were removed in 

greatest fractions of their whole-ash contents. About half of the total 

Cl~ and SO^2 was removed, much less of total F~, and almost no PO^3. 

The soluble material in the deionized water leachate, and the material 

removed by rain in the field, was composed of electrically equivalent 

amounts of the major cations and anions found in common salts, suggesting that it may represent a layer of material that mantles grains 

of igneous material, but is distinct from them in composition and 

solubility. Nearly the same amounts of most cations and anions were 

readily removed by leach treatments of widely varying water to ash 

ratios, and by rain in the field, indicating presence of a definite quantity of easily dissolved surficial material.

Larger fractions of whole-ash contents of elements were put into 

solution by the 4-hour acid leach treatment than by the deionized water 

leach treatment, but the increases in the amounts were different for 

various elements. The most abundant elements in the acid leachate 

were Ca, Fe, Al, Na, P, K, Mg, and Si. The acid leach removed slightly more Cl~ and SO^2, somewhat more F~, and much greater amounts 

of PO~3 than did the deionized water leach. Much of the acid-soluble 

material probably came from surficial material coating primary igneous grains but, unlike the deionized water leach solute, anions were 

insufficient to electrically balance the cations in the acid leach solute.

Exchange reactions, in which protons displaced cations from grain 

surfaces, were evidently a source of cations to the acid leach solution. 

Increased pH values after the completion of leach treatment show that 

the quantities of electrical equivalents of protons consumed accounted 

for a large fraction of the excess cations put into solution.

There are highly significant positive and negative statistical correlations between Ca, Si, and Na in the whole ash (elements indicative 

of lithologic type) and amounts of leachable species removed by the 

water and acid leach treatments. Dark-colored ash (high Ca, Fe, Mg; 

low Si, Na) released a greater amount of material to leaching 

treatments than did light-colored ash (high Si, Na; low Ca, Fe, Mg).

Much material initially present on the ash as soluble salts was released to the water and soil environments in a single pulse shortly 

after deposition of the ash blanket. If one or two pore volumes of interstitial solution from the ash were added to the solution present in 

a typical soil, there would be a net increase in concentrations of some 

elements that are either innocuous or beneficial to plant nutrition (K, 

Mg, Cu, Fe, and Zn), and either a net decrease or no large change in 

concentrations of some elements of "environmental concern" (Ba, Na, 

and Mo). The chemistry of some small bodies of water may have been 

more significantly altered after the ash fall, and some biotas may have 

been affected. A suite of elements similar in proportions to those 

yielded by acid leach treatment may be expected to be released over 

long periods of time in the low-pH zones near plant roots.

Species determined were removed from ash by water leach treatment in greater amounts than are reported in soils literature to be 

removed from common soils by similar treatment. However, repeated 

leach treatments of ash samples removed smaller amounts of solute 

than did the first treatment, whereas amounts of solutes from repeated 

extractions of soils are reported to change little. Analytical splits of 

ash samples yielded leach solutions of more consistent composition 

than splits of soil samples commonly do. This may be because ash 

is a simpler material than soil and lacks the clays, organic materials, 

oxide and hydroxide coatings, and long development histories of most 

soils.

INTRODUCTION

The May 18, 1980 eruption of Mount St. Helens, 

Wash., deposited an estimated half billion tons of airfall tephra over large areas of the States of Washington,

27
28 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

Idaho, and western Montana (Sarna-Wojcicki, Shipley, 

and others, 1981). Almost immediately after deposition, 

substances began to be leached from the ash by rain, 

soil solution, bodies of water, and the action of plant 

roots.

The present investigation of the leachate chemistry 

of the ash had two purposes. One was to determine the 

identity, amount, and sources of the leachable chemical 

substances likely to be yielded by the ash. The other 

was to provide a body of information to aid the work 

of others on the interaction of the ash particles with 

gaseous or aerosol phases that may condense upon them 

during times of eruption and atmospheric transport, 

possibly forming water-soluble coatings on grain surfaces and in interstices.

We performed leaching experiments on selected 

samples of the ash in the laboratory using both deionized water and dilute solutions of strong acid. The deionized water leaches were intended to approximate 

conditions in the field under which the ash would be 

washed by rain or soaked by soil solution at near-neutral 

pH, after incorporation of ash into soil. The acid leaches 

were intended to more closely approximate conditions 

in the microzones surrounding plant roots where pH 

values can be low (pH 2 to pH 4).

ACKNOWLEDGMENTS

We thank our USGS colleagues and the individuals 

who provided us with samples collected shortly after 

deposition. Special thanks go to Mr. and Mrs. Homer 

Evers, who collected the Almira, Wash., time-sequence 

samples. We thank Hans Claasen, David Dethier, and 

Gerald Feder for scientific discussions that affected the 

course of the experiments and the interpretation of the 

results. We would like to acknowledge F. E. Lichte and 

George Riddle who worked on the inductively coupled 

plasma spectroscopy analyses.

SAMPLE COLLECTION AND TREATMENT

A large number of ash samples from the May 18,1980 

eruption of Mount St. Helens was obtained over a wide 

area of deposition, from on-site colleagues and 

volunteers during or immediately after deposition, and 

by the authors several weeks later. A map of sampling 

localities is included as figure 1, chapter A, of this

volume. We carefully documented the collection and 

storage procedures and the postdepositional history for 

each sample, anticipating that the leachable chemical 

characteristics of ash samples could be easily altered 

in a short time following deposition. Whenever possible, samples were put into clean tightly sealed plastic 

or glass jars at the time of collection and kept in them, 

undisturbed, until aliquots were taken for analytical 

preparation.

Large numbers of the samples represent the three 

following natural groupings: (1) ash that fell at progressively increasing distances from the source; (2) ash 

from the same location before and after rainfall; and (3) 

ash that was collected during successive time increments (referred to herein as time-sequence samples) 

at single sites. Suites of five samples from Almira, 

Wash., and two samples from Missoula, Mont., represent the time-sequence samples. The Almira samples 

were carefully collected on a plastic table cloth and 

transferred and sealed into sterile glass jars at successive time intervals throughout the ash fall. Due to 

this careful and expedient collection procedure, the 

Almira ash did not have any contact with soil and little postdepositional contact with the atmosphere. 

Because of the uniquely favorable and well-documented 

circumstances of collection of the samples from Almira, 

they are, despite their paucity, treated in much of this 

report as yielding results of quality and importance 

equal to those of other more numerous pre-rain samples 

used in this study.

We used 39 samples for the deionized water and acid 

leach studies. These were selected from 69 samples (59 

originals plus 10 analytical duplicates) that were analyzed for whole-ash chemical composition and discussed 

in chapter A of this volume. In the present study, the 

leachate anions were determined by 1C (ion 

chromatography) and the cations by ICP (inductively 

coupled plasma) spectroscopy. Specific laboratory 

methods and 1C techniques are described in the 

"Laboratory methods" section of this report. A complete tabulation of all chemical and leachate data for 

individual samples, with an explanation of source location, exposure history, and other information, is given 

in Appendix C.

The samples were analyzed in a partially random 

order, so that systematic error (such as "machine drift") 

through the analytical sequence would be largely converted to random error. However, samples belonging 

to a natural subset or grouping, such as the timesequence sample suite for Almira, Wash., were placed 

fairly close to each other in the analytical queue, to 

minimize drift in accuracy between samples whose 

values would be compared.
LEACHATE CHEMISTRY OF ASH 29

LABORATORY METHODS DEVELOPED

FOR MOUNT ST. HELENS WATER AND

ACID LEACHING STUDIES

By S. A. WILSON and C. A. GENT

INTRODUCTION

The purpose of this work was to develop general 

laboratory methods for quantifying trace levels of 

anions and cations (using 1C [ion chromatography] and 

ICP-AES [inductively coupled plasma-atomic emission 

spectroscopy], respectively) under specific environmental conditions for the Mount St. Helens ash samples. 

These data are important in understanding the intricate 

associations between anions and cations, and are critical 

in assessing the long-and short-term impacts of the 

eruption on the environment.

To properly simulate environmental effects, two 

leaching solutions were selected to approximate conditions to which the ash material would have been subjected. The first solution tested was deionized water, 

which is believed to model the effect of rain or river 

water on the ash. The second solution was sulfuric acid, 

which was selected because significant quantities of 

acidic gases (SO2 , H2S) emanated from the volcano 

prior to, during, and after the eruption (Casadevall and 

others, 1981; Evans and others, 1981). The combination 

of these acidic gases with atmospheric moisture will 

result in the formation of sulfuric acid. The effect of 

sulfuric acid is significant because it will impact the ash 

directly through changes in pH or exchange reactions, 

which will affect the extraction of selected anions and 

cations.

A second reason for the use of a sulfuric acid leach 

solution deals with the chemistry occurring at the plant 

root-soil interface. It is suggested that various organic 

acids are extruded at the root surface, which is in direct 

contact with the soil (Rovira and Davoy, 1971). These 

organic acids are important in the mobilization of 

nutrients, using chemical processes such as complexation or pH changes. Although sulfuric acid does not 

mimic all of these chemistries, it may serve as a useful 

model for the effect of acidity on the transport of 

nutrients from the ash.

Although the two solutions cannot approximate every 

environmental condition to which the ash would have 

been subjected, they point out the accessibility of ions 

to two important chemical conditions.

EXPERIMENTAL PROCEDURES 

LEACHING STUDIES

Initial studies conducted to optimize experimental 

conditions used samples collected in early Mount St. 

Helens eruption studies (Taylor and Lichte, 1980). The 

samples used were collected from Sunnyside, Anthanum, and Spokane, Wash., as well as Spaulding, 

Idaho. Details of their collection are reported by Taylor 

and Lichte (1980). Later experiments involving nitric 

acid leaches included a sample from Almira, Wash.

In investigations using deionized water and sulfuric 

acid, a half gram of ash material was placed in a 60-mL 

polyethylene bottle, and 7 mL of leaching solution 

(water or acid) was added. The bottle was sealed and 

placed on a Lab-Line junior orbit shaker1 operating at 

150 rpm. The solution was shaken for 4 hours, after 

which the solution was filtered using a 0.2 micron teflon 

filter. The filtered solution was split into two aliquots 

for 1C and ICP-AES analyses. Water leach solutions for 

ICP-AES analysis were acidified with 1 mL of 6 M 

HNO3 and stored in teflon test tubes.

ION CHROMATOGRAPHIC CONDITIONS

1C analyses used Dionex models 12S and 16 ion 

chromatographs. Instrument parameters were 100-mL 

injection loop, 138-mL/hr eluent flow rate, 0.003 M 

NaHCO3-0.0024 M Na2CO3 eluent, 3-100 /xS full 

scale settings, 3X250 mm S-l anion separator 

columns, 3X150 mm S-l anion precolumns, and a 

6X250 mm anion suppressor column. Chromatograms 

were recorded using a Houston omniscribe strip chart 

recorder. Standards were prepared in deionized water 

or acid to match the sample matrix. Deionized water 

standards and solutions obtained using deionized 

water leaches were spiked with a concentrated sodium 

carbonate-bicarbonate solution to match the chromatographic eluent. This spike addition was necessary to 

eliminate a water dip interference on chloride determinations.

Sulfate extraction studies conducted on an Almira, 

Wash., sample used a 0.009 M HNO3 extracting solution. The resulting solutions were analyzed using identical instrument parameters except for the use of S-2 

anion precolumns, S-2 anion separator columns, and an 

eluent of 0.003 M Na2CO3 and 0.0015 M NaOH.

xAny use of trade names in this report is for descriptive purposes 

only and does not imply endorsement by the U.S. Geological Survey.
30 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION 

SPECTROSCOPY CONDITIONS

ICP-AES analyses were performed using a Jarrell 

Ash Model 11760 Plasma Atomcomp ICP-AES. The 

62-channel system was equipped with a modified Babbington nebulizer and a Gilson peristaltic pump for sample and internal standard delivery. Instrument 

parameters, wavelengths, and precision values for the 

analysis of the Mount St. Helens ash have been reported 

(Taggart and others, 1981).

PH STUDIES

All pH measurements were obtained using a Beckman 

model 4500 digital pH meter and an Orion combination 

pH electrode. The system was calibrated at 25 °C using pH 4 and pH 7 buffers. All solutions were filtered 

prior to a pH measurement. In extraction versus time 

experiments for deionized water, pH values were recorded at 1-, 4-, and 20-hour intervals. In sulfuric acid 

leach experiments, samples were selected for pH 

measurement following a 4-hour extraction.

ACCURACY AND PRECISION

Errors associated with the analysis of each element 

are reported in Appendix D. In ICP-AES studies involving total elemental analysis, the accuracy of the 

analytical procedure was tested using U.S. Geological 

Survey rock standard G-2. Samples of G-2 were 

prepared for analysis using the standard acid digestion 

procedure. The resulting solutions were analyzed at the 

beginning and end of each group of Mount St. Helens 

samples. Other studies have reported ± 10 percent accuracy for ICP-AES analysis of whole-rock samples of 

Mount St. Helens ash (Taggart and others, 1981). Cation leachate studies should produce comparable accuracy and precision values.

Precision values for whole-rock and extractable anion 

concentrations were estimated in two separate studies. 

Precision estimates for anion concentrations in wholerock analyses by 1C were based on previous investigations (S. A. Wilson and C. A. Gent, unpub. data, 1982, 

1983). On the basis of these studies a recommended 

value of ± 10 percent is considered conservative for the 

total anion analyses. Precision values for anion determination in the extraction study were based on 

repetitive analysis of an Almira, Wash., sample. On the 

basis of these studies a precision value of 4 percent was 

observed for the anions examined.

DISCUSSION AND RESULTS

Laboratory methods used in this study were designed 

to examine the effect of leaching solution composition 

and time of extraction on the removal of ions from the 

ash. Design of an optimized experimental procedure was 

based on anion data accumulated using 1C. It was 

assumed that cations would have similar extraction 

trends as the anions. Initial experiments examined the 

effect of solution composition on anion extraction. In 

these studies a Richland, Wash., ash sample was 

leached with deionized water and 0.01 M and 0.1 M 

sulfuric acid solutions for 1 hour. The results are 

presented in figure 6. There was a significant increase 

in the amount of anions extracted using the acid solutions compared to the water leach. In addition, there 

was a slight increase in extractable anions as the acid 

concentration increased from 0.01 M to 0.1 M sulfuric 

acid. On the basis of these observations, a 0.01 M acid 

concentration was selected for the general laboratory 

procedure, since it is probably a better model for acid 

extraction than the 0.1 M acid leach.

100

0.02 0.04 0.06 0.08 0.1 

CONCENTRATION OF SULFURIC ACID, INM

FIGURE 6. Effect of acid concentration on the extraction of F~, Cl~, 

and PO^3 from the ash using deionized water (0 M H2SO4) and 

0.01 and 0.1 M H2SO4 and a 1-hour extraction time. Sample collected at Richland, Wash.

A second set of experiments designed to evaluate the 

optimum extraction time was conducted using 1-, 4-, 

and 20-hour leaching periods. Results of the extractions 

using deionized water and sulfuric acid are presented 

in figures 7 and 8, respectively. These data indicate that 

the major changes in extractable anion concentrations 

occur in the period between 1 and 4 hours. Because of 

these observations, the large number of samples, and
LEACHATE CHEMISTRY OF ASH 31

CONCENTRATION EXTRACTABLE F"5'" |rj EXTRACTABLE *O STS- IN PARTS MILLION % F~ CONCENTRATION PER THE ASH, IN ,

3 £f **" a! 2g OQ 5>MILLION £ INPARTSER ® pj CL

SSSfrJ-Tpe? r| fr§Ig?o° ° o 

eed for rapid sample analysis, a 4-hour 

1 was used in all subsequent studies, 

omparison of extractable anion concentra 

^ionized water and 0.01 M sulfuric acid le 

nted in table 9 for a Missoula, Mont., sa 

>arent that the acid leach extracted subsl

^^ SO" 2

.... 1 , 1 1 1 I 1 1 1

each intions us- 

;aches is 

mple. It 

bantially

2,000

Z

w

o

li1- -1

z =J

LU 5

U *

z oc

O LU

u °-

CM W

1,000 gf |

Q °-

z < z -

b w

3 LU m x

2 K 

u 

<

pX

LU

0 4 8 12 16 20 

LEACH TIME. IN HOURS

: 7. Effect of leach time on the extraction of F", Q", and SO^2 

the ash using deionized water. Sample collected at Spaulding,

0.

 - :

i , i , i , i , i

-* C 3WMCJ1 4> g C O0

0 CO o

3 EXTRACTABLE CAND PO CONCENTRATIONS IN THE ASH,

4

PER MILLION IN PARTS 

4 8 12 16 20 

LEACH TIME, IN HOURS

8. Effect of leach time on the extraction of F", Cl", and PO;3 

the ash using 0.01 M H2SO4. Sample collected at Spaulding,

n

more F~ and PO^3 than did the water leach. This increased extraction may be due to an exchange process 

in which SO^2 ions, or changes in pH, affect the solubility of specific compounds. The greater PO^3 extraction 

is especially significant as it can affect soil fertility by 

making PO^3 more accessible to plants. An examination of the Cl" data in table 9 reveals a different trend 

than that seen for PO^3 and F~. The lack of a major increase in extractable Cl~ was attributed to the presence 

of water-soluble chloro compounds such as sodium 

chloride or hydrochloric acid. These compounds would 

not need any exchange process or pH change to release 

Cl~ into solution. 

Information on the extractability of sulfate in an acid 

leach was not possible using the standard sulfuric acid 

extraction procedure. As a result, a modification to the 

acid extraction procedure was devised for an Almira, 

Wash., sample, using a 0.02 M nitric acid solution. 

Results are presented in table 10.

TABLE 9. Concentration of anions extracted from the ash using 

deionized water and 0.01 M HgSO4 leaching solutions and a 4-hour 

extraction time 

[Sample collected at Missoula, Mont. Leaders ( ), data not available due to nature of leaching 

solution]

Concentration of extracted anions 

(in pptn)

Deionized water 0.01 M_ H2SO^ 

leach leach

F" 19 100 

Cl~ 830 910 

PO^3 50 600 

SO^2 4,000

TABLE 10. Concentration of anions extracted from the ash using 

deionized water, 0.01 M H^SO4 , and 0.02 M HNO3 leaching solutions and a 4-hour extraction time 

[Sample collected at Almira, Wash. Leaders ( ), data not available due to nature of leaching 

solution]

Concentration of extracted anions 

(in ppm)

Deionized water 0.01 11 H2S04 0.02 11 HN03 

leach leach leach

F" 25 84 80 

Cl" 670 860 800 

PO^3 50 1,300 1,200 

SO^2 2,900 3,800
32 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

As seen in previously discussed studies comparing 

deionized water and acid leaches, the nitric acid leach 

extracted significantly more anions from the ash than 

did the deionized water leach. The nitric acid data mimic 

the sulfuric acid data and support the theory that 

anions are present in the ash material as adsorbed 

(water soluble) or chemically associated (ion exchange 

or precipitated) ions. This chemical association with the 

ash is apparently acid independent as the F~, Cl~, and 

POj3 concentrations are similar in both the nitric acid 

and sulfuric acid leaches. Extrapolating the results of 

the acid extractions to a soil environment containing 

certain organic acids, one could anticipate similar extraction phenomena. This would result in the gradual 

mobilization of ions long after the water-soluble ions 

have been removed.

As indicated previously, investigators have found 

acidic gases in the volcanic plume during the eruption. 

These acidic gases could condense on the ash and 

undergo subsequent neutralization or dissolution reactions. If these reactions are only partially complete, then 

there should be residual acid present on the ash. This 

residual acid could participate in subsequent reactions, 

and be monitored by changes in pH.

To examine this possibility, pH data were accumulated during extraction time studies involving the 

deionized water leach of various ash samples. The 

results for selected samples are presented in table 11.

TABLE 11. Changes in pH observed during ash extraction using 

deionized water leaching solution and 1-, 4-, and 20-hour extraction 

times

[Leaders ( ), data not available due to nature of leaching solution]

Observed pH changes

Sampling sites 1-hour 

extraction

4-hour 

extraction

20-hour 

extraction

Sunnyside, Wash.-

Ahtanum, Wash. 

Kali spell, Mont. 

Spalding, Idaho 

Spokane, Wash. 

3.83

3.63

3.72

4.17

4.87

4.01

6.70

4.87

4.87

7.13

6.58

7.69

7.06

6.67

The recorded pH increased significantly as the extraction proceeded from 1 to 20 hours. This pH change can 

be attributed to an initial release of acidic material adsorbed onto the surface of the ash, lowering the solution pH. The subsequent increase in pH is the effect of 

a slow ion exchange or neutralization process that 

removes protons from solution. This removal of protons 

should be accompanied by increases in cation or anion

concentrations in solution (2-3 ppm in solution). 

Although the neutralization or ion exchange affects 

may be slight, the variation in pH can have important 

implications for other solution reactions such as solubility or complexation.

The pH studies were later extended to sulfuric acid 

extraction studies to see if similar pH changes occurred. 

In these studies, samples were leached with 0.009 M 

sulfuric acid and the final pH values were compared to 

a blank run simultaneously. A pH change from 2.0 to 

2.8 was observed for the Ritzville, Wash., sample, which 

is typical of the change seen for other samples tested. 

This change in pH indicates that even under acidic conditions, neutralization or ion exchange reactions are occurring, which contribute to the ability of the acid leach 

to extract greater amounts of ions than the water leach.

SUMMARY

Procedures developed for leaching studies involving 

Mount St. Helens ash were based on initial experiments 

using 1C. Leaching experiments conducted with deionized water, sulfuric acid, and nitric acid monitored the extraction of F-, C1-, PC>43, and SO^2 using S-2 and S-3 

anion separator columns. These initial studies were 

designed to establish optimum experimental conditions, 

such as extraction intervals and leach solution concentrations.

Information accumulated during these initial experiments demonstrated the greater extraction efficiency of the acid leaches compared to the deionized water 

leach. This is especially significant in the case of F~ and 

PO^3. In addition to significant changes in anion extractions, important pH changes were also noted in both 

the acid and water extractions. These pH changes are 

useful in explaining some of the chemical processes 

observed during the experiments.

BACKGROUND AND LITERATURE 

DISCUSSION

Several researchers have recently documented the 

presence of water-soluble material on freshly erupted 

volcanic ash (Taylor and Stoiber, 1973; Rose and others, 

1973,1978, 1980; Rose, 1977; Smith, 1980; Smith and 

others, 1981; Smith, Zielinski, and Rose, 1982; Smith, 

Zielinski, and others, 1982). In these studies, fresh ash 

samples were subjected to a water wash and the 

resulting leachates were generally found to contain Ca, 

K, Mg, Na, Cl~, F~, and SO^2 with lesser amounts of 

Al, B, Ba, Br, Cu, Fe, Mn, Se, Si, and Zn. Models have
LEACHATE CHEMISTRY OF ASH 33

been developed to explain the presence, distribution, 

and chemical makeup of these water-soluble materials. 

Oskarsson (1978,1980) proposed a model based on the 

existence of three distinct temperature-dependent reaction regimes within an eruption cloud. Each regime accounts for a specific type of reaction involving acid 

magmatic gases (such as SO2, HC1, and HF). The 

characteristics and processes of the three regimes are 

as follows.

1. At the high temperatures that prevail during degassing of magma in the eruption vent or in the core 

of an eruption cloud, aerosol salt particles, primarily halides and sulfates, may form. The temperature 

limit for this salt formation process depends on the 

melting point of the particular salt being formed. 

These aerosol salt particles can be transported as 

suspended load. The presence of aerosol salt particles adhering to fresh ash from volcanoes in Central America has been confirmed by the use of 

scanning electron microscopy and energy dispersive X-ray analysis (Rose and others, 1973, 1980; 

Smith, Zielinski, and others, 1982). Naughton and 

others (1974) collected sublimates from directly 

above a lava fountain and found salt components 

consisting of chlorides, fluorides, and sulfates of the 

alkali metals and calcium.

2. In Oskarsson's intermediate temperature regime 

(below about 700 °C), surface adsorption of gaseous 

halogen acids (primarily HC1 and HF) onto 

solidified silicate material may take place.

3. In the lowest temperature regime (below 338 °C), 

sulfuric acid is stable and may condense as an 

aerosol by the following reactions:

SO2(g) 02(g) = S03(g)

SO3(g) + H2°(g) = H2SO4(1)'

Subsequently, at temperatures below 120°C, halogen 

acids are stable and may condense. Upon further cooling, acid condensates absorb water vapor to form dilute 

acids. These acid condensates may coat ash particles. 

Another model for the formation of soluble materials 

on ash particles, proposed by Rose (1977), involves the 

scavenging of acid aerosol droplets (primarily H2SO4 

and some HC1) by ash particles. In this process, 

scavenged droplets of dilute acid may leach soluble 

elements from the glass and mineral grains of the ash, 

leaving coatings of water-soluble material on their surfaces. Acid aerosol scavenging should be most active 

at intermediate distances from the source, where the 

number of acid particles is at a maximum, and least active both in the immediate vicinity of the vent, where 

aerosol droplets have not yet condensed from gases, and

at greater distances from the vent, where the aerosol 

is dispersed (Rose, 1977). The acid aerosol scavenging 

theory may provide a useful explanation for observations made in a study by Rose and others (1973), in 

which the amount of water-soluble material associated 

with the ash decreased with increasing distance from 

the source, despite the fact that ash collected far from 

the source was fine grained, and hence had a larger surface area. They also noted that ash particles from the 

final stages of a pyroclastic eruption were coated by the 

largest amount of water-soluble material. Rose and 

others (1980) and Smith, Zielinski, and others (1982) 

have confirmed the presence of acid coatings on ash particles using scanning electron microscopy on small particles (<25 nm in diameter) directly sampled by aircraft 

in volcanic eruption clouds.

In another prevalent model, Taylor and Stoiber (1973) 

suggested that, upon decrease of pressure and 

temperature after an eruption, volatile compounds, such 

as the halides of Cu, K, Na, and Zn, condense as watersoluble coatings on ash particles. A combination of this 

condensation process and acid aerosol scavenging by 

ash particles may be analogous to fumarolic incrustation formation processes described by Stoiber and Rose 

(1974).

The relative contributions of the aforementioned 

models and processes to resolving the formation 

mechanisms for soluble components associated with 

volcanic ash is, as yet, unclear. This may be attributed 

to the complexity and range of conditions possible in 

an eruption cloud.

Enrichment of certain elements in the water-soluble 

components associated with volcanic ash has been 

reported in the literature. Smith (1980) performed 

aqueous extractions of filters used to collect aerosols 

from volcanic eruption clouds. He calculated the enrichment factors for these water-soluble elements and found 

that Cd, Cu, Pb, V, Zn, Cl~, F~, and probably S (as 

sulfate) were enriched in the water-soluble component 

relative to the composition of bulk ash.

Several elements reported to be associated with 

volcanic ash are the same as those reported to be enriched in studies of atmospheric participates not directly associated with volcanic activity. Zoller and others 

(1974), Duce and others (1975), and Maenhaut and 

others (1979) sampled aerosols in remote areas far from 

cities, whereas Miklishanskiy and others (1977, 1978) 

sampled city air. These studies all produced comparable 

results: enrichment of the aerosols with respect to a 

similar suite of elements (Ag, As, Au, Br, Cd, Cu, Hg, 

In, Pb, Sb, Se, V, W, and Zn) in comparison to baseline 

crustal rock and seawater abundances. Several researchers have found this similar suite of elements to be 

abundant in atmospheric particles from active volcanic
34 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

regions (Cadle and others, 1979; Mroz and Zoller, 1975; 

Lepel and others, 1978). There is a general similarity 

between the results of these studies, and some authors 

proposed that volcanism may be an important source 

of the reported enrichment of several elements in atmospheric particulates not directly associated with 

volcanic activity (Duce and others, 1975).

RESULTS AND DISCUSSION

In the following sections we discuss the amounts of 

material removed from different types of ash samples 

(1) by the two artificial leach treatments used in this 

study, (2) by other commonly used leaching techniques, 

and (3) by rain. Then we attempt to evaluate the nature 

and sources of the material removed from the ash 

samples by the leaching solutions, paying detailed attention to the implications of the electrochemical relationships in the leachates.

AMOUNTS OF MATERIAL REMOVED BY 

WATER AND ACID LEACHING TREATMENTS

Table 12 presents data on the amounts of chemical 

species removed by the deionized water and acid leach 

treatments for ash samples from Washington, Idaho, 

and Montana, and for time-sequence samples from 

Almira, Wash., none of which had been rained on at the 

time of collection. All leachate amounts presented in the 

tables and text of this report are as micrograms of element (or species) per gram of ash (ppm ash). The most 

abundant species in the deionized water leachate were: 

SO42 (represents 800-2,900 ppm ash), Ca (550-1,000 

ppm ash), Cl- (480-670 ppm ash), Na (320-440 ppm 

ash), Mg (60-100 ppm ash), K (60-100 ppm ash), NO§ 

(80-100 ppm ash), Si (20-30 ppm ash), Mn (9-17 ppm 

ash), and F~ (13 ppm ash). This ranking of species in 

order of abundance corresponds with that found by 

Smith, Zielinski, and Taylor (1982) for fresh Mount St. 

Helens ash.

Those species present in the greatest amounts in the 

acid leachate were: SO^2 (1,200-3,900 ppm ash), Ca 

(1,700-2,700 ppm ash), PO;3 (900-1,300 ppm ash), Fe 

(470-760 ppm ash), Cl~ (530-820 ppm ash), Al (450-570 

ppm ash), Na (440-530 ppm ash), P (360-470 ppm ash), 

K (340-510 ppm ash), Mg (320-490 ppm ash), and Si 

(220-290 ppm ash). Fe and Al concentrations were 

below the analytical limit of detection in solutes of the 

deionized water leach treatment, yet were among the 

most abundant elements in the acid leachate. All

removed in greater amounts by the acid leach treatment 

than by the deionized water treatment.

The two leach treatments removed chemical species 

in different percentages of their whole-ash contents 

(table 12). A large percentage of the leachable amounts 

of the anions Cl~ and SO^2 was dissolved by the water 

leach; that is, the harsher acid leach removed only 

slightly more of these species than did the water leach. 

However, in the case of the minor anion F~, the acid 

solution removed several times more than the deionized 

water leach. As for PO^3, the deionized water leach 

removed no detectable amount, whereas it was removed 

by the acid leach in amounts equal to about 50 percent 

of its whole-ash content.

The rankings of chemical species (orders of abundance) in the leachates were different between the two 

leach treatments. Table 13 is a ranking of the abundances of chemical species removed by deionized water 

and acid leaches as a percentage of the total amount 

present in the ash. The equivalent information is 

presented graphically in figure 9. Ni, Co, Mn, and Ca 

lead the ranking for elemental species in the deionized 

water leach, having been removed in amounts representing about 2-6 percent of their totals. The alkali and 

alkaline earth metals Li, Na, and K, and Mg, Sr, and 

Ba, respectively, were all removed in lesser fractions, 

but in amounts greater than 0.4 percent of their totals. 

V, La, Y, Cu, Zn, Fe, Al, and Si were removed by deionized water leach in fractions of their whole-ash totals 

smaller than 0.6 percent. This information is consistent 

with that presented by Dethier and others (1981) for 

Mount St. Helens ash.

For the most part, whole-ash fractions of elements 

released by the acid leach treatment are larger than 

those released by the deionized water leach treatment, 

but the range in magnitude of acid leach values is great 

(table 13). There is a group of elements that is removed 

from the ash much better by acid than by water, and 

another suite removed more nearly equally by the two 

leach treatments. Cu, Fe, Zn, Al, La, Y, and PO^3 are 

removed by acid leach in amounts more than a factor 

of 24 times greater than amounts removed by deionized 

water leach. For Si, V, Mn, K, Ca, Mg, Sr, Li, Ni, Co, 

and Na, the factor is smaller, ranging from about 10 

times more for Si to about unity for Ni, Co, and Na. 

Barium concentrations are generally less in the acid 

leach solution, probably because its solubility is controlled by the presence of sulfate. This separation of 

elements into two groups is clear from figure 9.

We expect that, in a natural setting, amounts of 

elements leached by our deionized water treatment 

would be removed in the surface environment before the 

ash was exposed to harsher leachiner solutions, snoh as
TABLE 12. Average amounts of components removed from the ash by water and acid leaching solutions

[Values for Washington, Idaho, and Montana are an average of analyses of 19 samples taken at varying distances from volcano (Randle, Ritzville, and Spokane, Wash.; Coeur d'Alene, Emida, and St. Ma

except that only nine samples were used for Cl~, F~, NO*, PO~3, and SO'2. Of these samples, some are members of closely spaced pairs, considered to be "sampling replicates." Values for Alm

five time-sequence samples, plus one sample analyzed in duplicate, for a total of six samples; each was collected and sealed immediately after fall. Averages include some analyses of both splits of singl

by inductively coupled plasma spectroscopy unless otherwise noted: star (*), determined by X-ray fluorescence. Specific conductance of water leach solution equals 0.39 micromhos/cm for the Wash

samples', and equals 0.65 micromhos/cm for the Almira, Wash, samples. Leaders ( ), value not determined; n, number of samples analyzed]

Washington, Idaho, and Montana pre-rain ash

Components whoie-ash Amount removed 

content as ppm of whole ash

Al

Ba

Ca

Co

Cu

Fe

K

La

Li

Mg

Mn

Na

Ni

P

Si

Sr

V

Y

Zn

ciF~

N03

P04 3

S042

*8.

390

*3.

10.

47

*3.

*1.

18

27

*1.

*.

*3.

12

*.

*30.

430

69

18

71

2 1,130

270

<500

2,100

1,540

Water leach

7 pet <10

ppm 4.3

2 pet 550

8 ppm .28

ppm <.l

0 pet <10

3 pet 57

ppm <.l

p pm .26

0 pet 58

045 pet 8.7

3 pet 320

ppm .7

078 pet <10

pet *20

ppm 2. 1

ppm !.17

ppm <.l

ppm <.l

ppm 480

ppm 13

ppm : 77

ppm <150

ppm 800

Acid leach

n=19

450

2.0

1,720

.35

7.2

470

340

2.4

'.50

320

42

440

!.5

360

220

5.3

1.2

2.4

4.2

n=9

530

48

X 54

900

4 1,200

samples

Amount removed as a 

percentage of amount of 

element in whole ash

Water leach

<0.01

1.1

1.7

2.6

<.2

<.03

.4

<.6

1.0

.6

1.9

1.0

5.8

<1.3

.007

.5

.25

<.6

<.l

43

5.0

<7.1

52

Acid leach

0.51

.51

5.4

3.2

15

1.6

2.6

13

1.9

3.2

9.3

1.3

4.2

47

.07

1.2

1.7

13

5.9

47

18

43

4 75

Almira, Wash. , pre-rain

Whole-ash 

content

Amount 

as ppm of

Water leach

*9.

340

*3.

13.

49

*3.

*1.

18

24

*1.

*.

*3.

19

*.

*29.

500

85

19

75

1,490

310

<500

2,420

8,650

0 pet

ppm

8 pet

7 ppm

ppm

5 pet

1 pet

ppm

ppm

29 pet

054 pet

2 pet

ppm

095 pet

pet

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

<10

4.8

1,030

.33

<.l

<10

100

<. 1

.52

103

16.5

440

.75

<10

30

3.7

.18

<.l

<.l

670

13

1 97

<150

2,870

removed 

whole ash

Acid leach

n=6

570

2.2

2,700

.58

5.6

760

510

3.7

.97

490

74

530

1

470

290

7.8

1.6

3.5

4.9

n=6

820

77

1 S7

1,290

3 3,850

ash sam

Amou

percen

eleme

Water l

<0.0

1.4

2.7

2.4

<.2

<.0

.9

<.5

2.2

.8

3.1

1.4

3.9

<1.1

.0

.7

.2

<.5

<.l

45

4.2

<6.2

33

^When appropriate, individual samples registering below instrumental detection limit were assigned values 0.7 times t

and then used with other values to obtain average, 

o 

Average of eight samples.

Average of one sample and its analytical duplicate for HNO-j leach. 

Sample from Ritzville, Wash., for HN03 leach. 
36 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

2 o*-* LU y u f=

°- Z 70'

Z ~ .

I

I 0

^ LU 60

LU

-" OC 

O j_ 

U < 50 

< $

> >

ii 40

i|

^ Lu 30

2 -5 20

SS 10

§ z

0 0 n

1

__ l

<r

-

-

_ 

ii i! i i * T T t f i

Cu Fe Al Zn P La Y Si V K Mg Mn Ca Sr Li Na Co Ni Ba

 i" OW

£ Z 70

U LU 60

LU 

_l CC

Q H 

0 < 50

m m

Q Q 40

LU LU 

0 0

LU LU 30 

OC EC

1- hZ Z

H !| 20

LU LU

-1 _l 

LU LU

SS 10

1- hz z

O O n

i

h t 1

- * I

1 J

_

fi ' 

i i i i i * T ? T f t ,

Fe Al Cu Zn P La Y Si V K Mg Mn Ca Sr L\ Co Ni Na Ba «i <i

FIGURE 9. Ordered plots of ratios (amount of element removed by 

acid leach -=- amount of element removed by water leach) for two 

suites of ash samples not affected by rain on the ground. Plotted 

points represent average values for A, 19 samples from Washington, 

Idaho, and Montana, and B, six samples from Almira, Wash. Order 

of elements is slightly different for the suites. Arrows pointing 

upward indicate that water leach values are lower limits.

acid leach treatment of this study). Thus, in some cases, 

our deionized water leach concentrations should be subtracted from our acid leach concentrations before the 

data are applied to projected natural situations. 

However, the overall contribution of chemical species 

to the soil-plant system by the ash may commonly be

TABLE 13. Ranking of abundance of chemical species removed from 

the ash by water and acid leaches, as percent of total whole-ash content 

[Data in percent. Sample descriptions and original data presented in table 12. n, number 

of samples averaged. Starred (*) values represent an average of nine samples]

Water leach Acid leach

Wash., Idaho,

and Mont.

(n=19)

Almira, Wash. 

(n=6)

Wash., Idaho,

and Mont.

(n=19)

Almira, Wash. 

(n=6)

Ni 

Co 

Mn 

Ca 

Ba 

Li

Na

Mg

Sr

K

V

La

Y

Cu

Zn

Fe

Al

Si

5.8 

2.6 

1.9 

1.7 

1.1 

1.0

1.0

.6

.5

.4

.25 

<.6

<.6 

<.2 

<.l 

<.03 

<.01 

.007

Ni 

Mn 

Ca 

Co 

Li 

Ba

Na

K

Mg

Sr

V

La

Y

Cu

Zn

Fe

Al

Si

3.9 

3.1

2.7 

2.4 

2.2 

1.4

1.4

.9

.8

.74

.2 

<.5

<.5 

<.2 

<.l 

<.03 

<.01 

.01

Cu

La

Y

Mn

Zn

Ca

Ni

Co

Mg

K

Li

Fe

Na 

Sr 

Al 

Ba 

Si 

V

15

13

13

9.3

5.9

5.4

4.2 

3.2 

3.2 

2.6 

1.9 

1.6

1.3 

1.2 

.51 

.51 

.07 

1.7

La

Y

Mn

Cu

Ca

Zn

Ni

K

Co

Li

Mg

V

Na 

Sr 

Ba 

Al 

Si 

Fe

21

18

14

11

7.0

6.5

5.3 

4.6 

4.2 

4.0 

3.8 

1.9

1.7

1.6

.7

.6

.1

2.2

so

Cl

F~

PO

-2 

4

4

*52

*43

*5.0

*<7.1

Cl~ 45

S072 33

F~ 4

P°43 < 6

.2

.2

Cl

PO

F~

-

-3

4

*47

*43

*18

Cl

PO

F~

~

-3

4

55

53

25

equal to the maximum removable amounts presented 

in this study (amount removed by acid leach treatment). 

If the deionized water leach solute concentrations for 

each element are subtracted from acid leach solute concentrations, the ranked order of element concentrations 

is nearly the same as for acid leach.

POSSIBLE SOURCES, NATURE, AND

SOLUBILITY OF MATERIAL REMOVED BY

LEACHING TREATMENTS

The possible sources of material removed by leach 

solutions are the following: (1) various amorphous or 

soluble coatings present on igneous surfaces; (2) particles of igneous minerals and volcanic glass; (3) older 

mineral and lithic material from the volcanic cone; or 

(4) combinations of these. Readily soluble surficial 

deposits on ash particles may have formed from fluid 

or gaseous phases during suspension of the particles in 

air, or may have resulted from the in-situ leaching of 

the particles by adsorbed acids (as was described in the 

"Background and literature discussion" section of this
LEACHATE CHEMISTRY OF ASH 37

report). Smith and others (1981) reported that watersoluble surface deposits of freshly erupted volcanic ash 

from several different eruptions were important in the 

initial release of B, Ba, Cd, Cu, F~, Pb, and Zn from ash 

to aqueous solution, but that Li, Si, U, and V were 

released to solution less rapidly, primarily through the 

dissolution of glass. Smith, Zielinski, and Taylor (1982) 

found similar results for fresh Mount St. Helens ash. 

Soluble onions in ash from both before and after the 

May 18, 1980 eruption of Mount St. Helens have been 

discussed in the literature (Stoiber and others, 1980, 

1981). A 2-year weathering study of the Mount St. 

Helens volcanic ash has been conducted by White and 

others (1986).

Defining the relative contributions of the possible 

sources of solute to different leaching solutions is of interest because soluble salts are likely to be removed 

from the ash and released to soil and hydrologic environments by a single rainfall event at the beginning 

of the weathering history of the deposited ash. The 

mineral grains would be broken down and their constituents released more slowly in the plant-root environment.

The following kinds of information may help 

distinguish whether single species, or groups of species, 

in the solutes from the two leach treatments have soluble surficial materials or igneous mineral phases as their 

primary sources.

1. Whether a species is readily removed by mild leach 

solution.

2. Whether there are great differences between 

amounts of species removed by treatments with 

widely varying solution: ash ratios.

3. Whether the cations removed from the ash are electrically balanced by anions associated with common salts; alternatively, whether it appears that 

hydronium ions from the leaching solution have 

replaced cations from mineral grain surfaces such 

that, in the solute, these cations are in excess of 

salt-associated anions removed from the ash.

4. Whether there are significant correlations between 

certain cations and anions in the leachate solutions 

such that cation-anion associations might be 

inferred.

5. Whether there is wide variation in leach solute composition from sample to sample for such key ratios 

as Ca/Sr. This ratio would be expected to be fairly 

consistent for solute derived from a homogeneous 

assemblage of igneous phases.

6. Whether there is a great difference between amounts 

of species removed from ash by deionized water and 

acid leach treatments.

These points will be discussed in order in the following

sections.

SPECIES READILY REMOVED BY DEIONIZED WATER 

LEACHING TREATMENTS AND BY RAIN

The rapid release of a species to a mild leaching solution such as deionized water, or the ready removal of 

an element from the ash by rain, would indicate that 

the major source of the element was water-soluble surficial material. The alkali and alkaline earth metals Li, 

Na, and K, and Mg, Ca, Sr, and Ba, respectively, (and 

possibly also Mn, Co, and Ni), all removed by water 

leach in amounts greater than 1/2 percent of their wholeash totals (tables 12 and 13), may be important constituents of the readily soluble surficial coatings on 

volcanic ash particles. The anions SO^2 and Cl~ (and 

possibly NO^), removed in amounts of as much as 

about 50 percent of their whole-ash totals, are major 

constituents of the water-soluble surficial material.

Daily rainfall records for the Ellensburg, Moses Lake, 

and Ritzville, Wash., sites are summarized in table 14, 

where the data are presented in inches, as published (National Oceanic and Atmospheric Administration, 1980a, 

b). About 0.8 inches (2 cm) of rain fell at Ellensburg, 

about 2 inches (5 cm) at Ritzville, and about 4 inches 

(10 cm) at Moses Lake during the month-long interval 

between deposition and collection of those samples of 

ash affected by rainfall on the ground. On May 30,1980, 

2.25 inches (6 cm) fell at Moses Lake, the greatest oneday precipitation at any site in the State during that 

month.

TABLE 14. Daily rainfall at ash collection sites in Washington State 

during the time interval between deposition and collection of 

some ash samples

[Data in inches; 1 in.=2.54 cm. Leaders (--), no rainfall. No rain fell on omitted dates. From 

National Oceanic and Atmospheric Administration (1980a, b)]

Ellensburg Moses Lake Ritzville

May 

May 

May 

May 

May

May 

May 

May

21

22

23

25

26

27

28

30

June 9

June 12

Jun e 13

June 14

June 15

June 16

June 17

Total0.01 

.04 

.07

.10 

.01

.04 

.01

.18 

.12

.20 

0.78

0.05 

.40

.52

.09

2.25

.42 

.05

.19

3.97

0.22

.69

.44

.30 

.04 

.02

.05 

1.76
38 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

Ash that lay on the ground in the field for several 

weeks before collection contributed smaller amounts of 

certain chemical species to the water and acid leaches 

than did ash collected immediately after deposition. We 

believe that washing by rainfall removed appreciable 

amounts of these chemical species from the ash that was 

collected several weeks after deposition. The amounts 

of elements removed by rain were evaluated by observing the differences in amounts extracted from suites of 

pre-rain and post-rain samples from approximately the 

same locations. Within broad limits, rainfall apparently removed most species in about the amounts suggested by deionized water leaching experiments. Table 

15 presents data for anions removed by both water and 

acid leach treatments from pre-rain and post-rain ash 

samples from Idaho and from Ritzville, Wash. Table 16 

presents similar data for cations.

Judging from the data of the water leach, rain apparently removed large amounts of Cl~ and SO^2 (table 

15); Cl~ was removed to the greatest extent. Estimates 

could not be made for NO§ due to imprecise data. The

cation data for the water leach treatment (table 16) show 

that appreciable percentages of water-leachable Li, Na, 

K, Mg, Ca, Sr, and Mn were removed by rain. Mn and 

K were removed to the greatest extent. The amount of 

rainfall that came into contact with the ash between 

times of deposition and collection was clearly less than 

the 14:1 deionized water-to-ash ratio (by weight) used 

in the laboratory treatment. Also, the contact time of 

the rain water with the ash particle surfaces was probably quite short due to the permeable nature of the ash 

blanket. And, the 4-hour agitation time used in the 

laboratory was most likely a more rigorous treatment 

than the ash was subjected to in the field. Therefore, 

the similarity in amounts of material removed from prerain samples by the water leach treatment and from 

post-rain samples by rain suggests that there was a 

discrete and limited amount of soluble material on the 

ash that was susceptible to removal by even a slight 

exposure to water.

Judging from the data of the acid leach, a harsher 

treatment that removes larger quantities of material

TABLE 15. Effect of rain on amounts of anions removed from the ash by water and acid leaches

[Values in ppm removed from whole rock unless otherwise noted. All determinations by ion chromatography. Leaders ( ), estimates were not made because of imprecise data. Values 

in parentheses are results of duplicate analyses, performed on split of original sample. When appropriate, individual samples (starred (*)) registering below instrumental detection limit 

were assigned values 0.7 times the detection limit and then used with other values to obtain average]

Water leach species Acid leach species

Cl SO 2

Ritzville, Washington

Pre-rain samples:

ODWRZY10 (ODWRZY1X) 20 (10) 580 (560) 180 «50) 870 (820) 48 (48) 750 (680) 65 «50) 900 (830) 

ODWRZW10 14 480 <50 1,000 52 290 78 900 

Average 15 525 925 50 505 -- 885

Post-rain samples:

LRWRZZ10 10 15 160 380 46 41 <50 850 

LRWRZZ20 (LRWRZZ2X) 7 (6) 16 (18) <50 (56) 87 (110) 41 (42) 42 (46) 53 «50) 830 (880) 

Average 8 16 240 45 45 855

Summary:

Approximate difference

between pre- and

post-rain averages 7 510 685 5 460 30 

Approximate percent of

available amount

removed by rain 50 95 75 10 90 <5

Idaho

Average, pre-rain samples (four original 

samples; two analyzed 

in duplicate) 13 440 *87 700 48 500 *55 910

Post-rain sample

(one sample) 3 17 <50 32 36 6 <50 750
TABLE 16. Effect of rain on amounts of cations removed from the ash by water and acid leaches

(Values in ppm removed from whole rock unless otherwise noted. All determinations by inductively coupled plasma spectroscopy. NA, estimates not available because cations were present in con

detection limit. Leaders ( ), estimates were not made because of imprecise data. Values in parentheses are results of duplicate analyses, performed on split of original sample. When appropr

(*)) registering below instrumental detection limit were assigned values 0.7 times the detection limit and then used with other values to obtain average]

Water leach

Ca Mg Na K B Co Ni Mn Li Sr Cu 

Ritzville, Washington

Pre-rain samples:

Post-rain samples:

380 (360)

35 (70) 

7<;

60 (50) 350 (340) 54 (51) 

40 280 40 

48 313 46

<10 80 <10 

<10 (10) 80 (80) <10 (10)

QO

8.0 (12.9) 0.2 (0.3) 0.7 (0.5) 

9.7 .2 .9 

10 .2 .8

8.4 .2 .6 

1 1.9 (10.0) .3 (.2) .8 (.6)

7.1 (5.8) 0.2 (0.1) 1.6 (1.5) NA 

6.1 .2 1.7 NA 

6.3 .2 1.6 NA

.5 <.l .4 NA 

.3 (.7) <.! «.l) .2 (.3) NA

<; T MA

Summary:

Approximate difference 

between pre- and 

post-rain averages - 300 1.3

Approximate percent of 

available amount

Idaho

Average, pre-rain samples (four original 

samples; two analyzed

Post-rain sample

Acid leach

Ritzvlllp, Washington

Pre-rain samples:

Post-rain samples:

LRWRZZ20(LRWRZZ2X) 1,000 (1,000) 240 (230) 210 (200) 245 (230) 9.1 (6.6) <.l (.2) .2 (.6) 21 (22)

Summary: 

Approximate difference 

between pre-and 

post-rain averages 300 10 240 10 .3 >0 >0 10 

Approximate percent of 

available amount 

removed by r,iin - 20 5 55 5 5 >0 >0 35

Idaho

Average, pre-rain samples (four original 

samples; two analyzed

Post-rain sample

50 80

*0.2 1.5 NA 

<.l .8 0.5 

0.7 (0.6) 4.5 (4.3) 6.7 (6.6

<.l 4.2 7.2 

*.4 4.3 6.9 

.3 3.3 6.7 

.1 (.3) 3.n (3.0) 7.0 (6.4

.25 3.2 6.7 

.15 1.1 .2 

40 30 5 

0.2 4.4 8.2 

.2 3.0 5.3 
40 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

from the ash than the water leach, rain was potent 

enough to have leached about half of the Na, a third 

of the Li, Mn, and Sr, a quarter of the Ca, and a 

measureable amount of the Zn, Mg, B, K, Cu, and P 

available to the acid leach treatment (table 16). The 

anion data for the acid leach treatment (table 15) suggest that a large amount of Cl~ and a measureable 

amount of F~ were removed by rain. It is unclear 

whether appreciable amounts of NO§ and PO^3 were 

removed by rain because of imprecision in the data. 

SO^2 values were not available for these samples due 

to the use of H2SO4 as the leaching acid.

Of the four metals that yielded the greatest percentages of their total whole-ash concentrations to the 

deionized water leach (Ni, Co, Mn, and Ca) and of the 

six species that yielded the greatest percentages to the 

acid leach (La, Y, Mn, Cu, Ca, and Zn), as was shown 

in table 13, only Mn and Ca appear to have been removed in appreciable amounts during exposure in the field.

AMOUNT OF MATERIAL REMOVED USING DIFFERING

AMOUNTS OF LEACHING SOLUTION RELATIVE TO THE

AMOUNT OF ASH

Table 17 presents data on amounts of selected 

elements removed from fresh ash by the following three 

treatments: (1) the 4-hour 14:1 deionized water-to-ash 

ratio (by weight) leach extraction of the present study; 

(2) a 4-hour single-pore-volume deionized water column 

leach done by Taylor and Lichte (1980); and (3) a 24-hour 

4:1 deionized water-to-ash ratio (by weight) leach extraction done by Smith, Zielinski, and Taylor (1982). Also 

presented for later discussion are data by Bradford and 

others (1971) for amounts of these same selected 

elements removed from common soils by the saturated 

paste method. Analytical methods differ in these 

studies and, for that reason, comparisons of analytical 

data must be made only broadly, with proper allowances 

for relative error.

Table 17 shows that amounts removed from ash of 

the four major alkali and alkaline earth elements of interest (Na, K, Mg, and Ca) are similar in both the "largesolution-volume" (14:1 deionized water-to-ash ratio, by 

weight) leach extraction and the "small-solutionvolume" (single-pore-volume and 4:1 deionized waterto-ash ratio, by weight) experiments. The amounts 

removed in the "large-solution-volume" study are consistently slightly larger for the four metals, but the differences between the amounts removed in the 

"large-solution-volume" study versus the "smallsolution-volume" studies are much smaller than the differences between the volumes of water relative to ash.

This similar removal between the three studies suggests that a reservoir of water-soluble material is present as surficial coatings on the grains. Subsequent 

successive single-pore-volume leaches performed by 

Taylor and Lichte (1980) did not yield much more 

material to solution; only Ca, Si, and SO^2 were removed in significant amounts upon further leaching. 

The soluble surficial material seems to be rapidly and 

almost completely dissolved by both the "large-solutionvolume" and the "small-solution-volume" leaches in a 

4-hour period.

The trace alkali metal Li and the minor alkaline earth 

metal Sr adhered to the same pattern as the major 

metals previously discussed. Barium concentrations are 

dissimilar in the leach studies of ash, suggesting that 

Ba, the least soluble of the alkali and alkaline earth 

metals determined, may be reaching its saturation, as 

controlled by SO^2, in the "small-solution-volume" 

leaches. If so, much more Ba should be removed in the 

"large-solution-volume" leach experiment, in which 

there is about 13-14 times more water to hold the Ba, 

than in the "small-solution-volume" leach experiment 

and, in fact, the data indicate that about 50 times more 

Ba was removed. The numerical magnitude of the factor may be a result of analytical error, due to low concentrations or different analytical techniques, or a result 

of complications in the amounts and identities of the 

onions present. Observed solubility products for BaSO4 

are about 1.5 XIO'8 and 2.5X10'9 for the "smallsolution-volume" and "large-solution-volume" leach 

studies, respectively (using raw concentrations). Both 

products are larger than published saturation values for 

these ions. Amounts of Cu, Mn, and Si removed from 

the ash are also similar in the different studies. Boron 

values from the studies do not agree and may be a reflection of the determination difficulties for this element.

The evidence from comparing the results of the 

studies by Taylor and Lichte (1980) and Smith, Zielinski, and Taylor (1982) with those of the present study 

suggest that readily soluble surficial deposits on grains, 

rather than igneous mineral phases, are the primary 

sources of material in the deionized water leach solutes.

ELECTRICAL ION BALANCE IN THE LEACHATE SOLUTIONS

The electrical ion balance between cations and onions 

given up to solution by the ash may give information 

about the sources of material soluble to leach 

treatments of varying stringency. Table 18 presents 

electrical ion balance values for groups of samples in 

which material was removed by deionized water treatment or by rain. In deionized water leachates from 

samples collected immediately after deposition,
TABLE 17. Comparison of amounts of elements removed from the ash by large and small volumes of water, and from common soils by the satu

[All values in ppm of whole rock removed by the leach treatment. Values for leach method of this study were determined by inductively coupled plasma spectroscopy; values for column leach meth

were determined by spark source mass spectrometry; values for study of soils by Bradford and others (1971) were determined by conventional emission spectrometry. Samples of the present s

distances from Mount St. Helens (Handle, Ritzville, and Spokane, Wash.; Coeur d'Alene, Emida, and St. Maries, Idaho; Missoula, Mont.). Samples of study by Taylor and Lichte (1982) were co

Helena and Kalispell, Mont. Samples of study by Smith, Zielinski, and Taylor (1982) were collected at varying distances from volcano. All samples were collected before being wetted by rain. Soi

and others represent 30 California soils of varying type. Original values for materials reported by Taylor and Lichte, Smith and others, and Bradford and others were in form of leach solution c

converted to units of this table after consultation with G. R. Bradford. When appropriate, individual samples (starred (*)) registering below instrumental detection limit were assigned values 0.

then used with other values to obtain mean, n, number of samples analyzed. Leaders ( ), not available because of qualified data. Data in parentheses are semiquantitative. ND, not determin

14:1 water:ash leach Single-pore-volume column leach 

of present study of Taylor and Lichte (1980) 

Element (n=19) (n=3)

Al 

B

Ba

Ca 

Co

Cu

Fe

K

La

Li

Mg

Mn

Mo

Na

Ni

P

Si

Sr

V

Y

Zn

Mean

9.4

4.3

551 

.28

*.09

57

*.07

*.26 

58

8.7

__

322

.7

*20

2.1

*.17

Range

all <10 

3.3-15.4

2.2-6.7

280-1,100 

.2-. 4

<.l-.3

all <10

35-98

<.!-.!

30-100

2.9-18

all <.05

140-520

.2-1.0

all <10

<10-30

1.0-3.8

<.l-.3

all <.l

all <.l

Mean

(0.38) 

.79

.08

266 

.04

.15

.09

(47)

(.01)

.3 

56

9.5

.01

275

(.24)

.05

20

1.5

*.0007

.002

.28

Range

(0.17-C0.58) 

.44-1.08

.07-. 11

263-267 

.03-. 06

.09-.2

.06-. 11

(41)-(58)

(.002)-(.02)

.26-. 33 

52-63

7-12.8

.004-. 02

235-325

(.03)-(.58)

.01-. 11

17-22

1.2-1.7

<.0006-.0012

.0012-. 0029

.09-. 42

4:1 water :ash leach of Smith 

Zielinski, and Taylor (1982) 

(n=19)

Mean

ND 

ND

.15

440 

.02

.16

.38

ND

ND

.21 

48

7.6

.01

264

ND

ND

19

1.8

.0012

ND

2.0

Range

ND 

ND

.01-. 24

108-800 

0-.07

0-.48

0-.48

ND

ND

.01-. 52 

13.6-84

.8-13.2

0-.06

84-440

ND

ND

15-26

.4-2.9

0-.03

ND

.07-27

, Common soils 

Bradford and 

(n=

Mean

0.16 

1.2

.1

51 

.02

.02

.02

8.0

ND

.04 

15

.07

.3

210

.01

ND

2.0

.37

.03

ND

.03

Medi

<0.0

<.0

.0

24 

.0

.0

.0

4.0

ND

.0

5.0

<.0

<.0

18

<.0

ND

1.4

.0

.0

ND

.0
42 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

summed electrical equivalents of major cations measured (Na+ , K+ , Mg++, Ca++, and Mn++) are nearly 

identical to those of anions measured (F~, Cl~, NO§, 

PC>43, and SO^2), indicating dissolution of ionic salts. 

The data indicate slight excess of cation equivalents in 

water leach treatment solutes, about 1 percent in one 

group (19 samples from Washington, Idaho, and Montana) and about 7 percent in the other (6 samples from 

Almira, Wash.). The values in table 18 are averages for 

groups of samples rather than for a leach treatment of 

a single sample. Details of cation-anion electrical 

balances for water leach solutes from five selected single 

samples are presented in table 19. Values for cationanion balance were calculated from data yielded by two 

independent analytical procedures (1C for anions and 

ICP for cations). The slight electrical deficiency of 

anions relative to cations may be a result of analytical 

or other error, presence of anions that we did not consider, ion-exchange reactions between hydronium ions 

in the leaching solution and surface cations on mineral

TABLE 18. Electrical balances of cation and anion equivalents in 

deionized water leach solutes and in material apparently removed 

from the ash by rain

[Data in milliequivalents per 10s g ash. Amounts of ions removed by rain were inferred from 

differences in water leach availability from three samples collected before and three 

samples collected after exposure to rain at same location. ND, not detected; n, number 

of samples averaged]

Material removed by water leach from ash samples not 

exposed to rain

Wash., Idaho, and Mont. Almira, Wash. 

(n=19) (n=16)

Na+ 14.0 F 0.6 Na+ 19.1 F 0.7

K+ 1.5 Cl~ 13.2 K+ 2.6 Cl~ 18.9 

Mg++ 4.8 SO^ 2 30.2 Mg++ 8.5 SO^2 59.7 

Ca++ 27.5 PO^3 ND Ca++ 51.3 PO^3 ND 

Mn++ .3 NO 3 .9 Mn++ .6 NO^ 1.6

Total 48.1 44.9 82.1 80.9

Material apparently removed from ash samples by rain

Ritzville, Wash.

Cation Anion

Na+ 10.6 F~ 0.4 

K+ <1.0 Cl~ 14.8 

Mg++ <3.3 SO^ 2 14.7 

Ca++ 15.7 PO^3 ND 

Mn++ .2 NC>3 .1

Total <30.8 30.0

grains (Petrovic and others, 1976), slight dissolution of 

mineral phases, or a combination of these. Anions such 

as OH", negatively charged silicon species, HCO§, and 

CO§2 can be associated with the dissolution of minerals 

or glass but, because of the proton condition (nearneutral pH), it is not possible that any of those species 

are abundant in the water leach solutes. Replacement 

of cations from surfaces of grains of minerals or glass 

by hydronium ions of the deionized water leach solution of near-neutral pH could have had only a small effect; however, if a solution were CO2 buffered, more 

hydronium ions could be available. The cation NH f 

was not measured. Taylor and Lichte (1980) reported 

NH^~ concentrations to be low in their water leach 

solute. Organic acids and ligands may have some importance in influencing the cation-anion balance, 

depending on the degree of exposure of the ash to 

burned organic materials. Organic species in ash 

leachates are discussed by McKnight and others (1981). 

For the material apparently removed by rain in the 

field (table 18, six samples from Ritzville, Wash.: three 

collected before rain, three collected after rain), the 

electrical ion balance is also close. We have previously 

commented on the possible relative stringencies of the 

rain and the deionized water leach treatments. Rain 

apparently removed one-third to one-half of the

TABLE 19. Electrical balances of anion and cation equivalents in 

deionized water leach solutes from selected ash samples

splits from Almira, Wash. ODWRZY10 is from Ritzville, Wash. These three samples 

were collected before exposure to rain. LRIHAZ10 and LRWRZZ2X are from Harrison, 

Idaho, and Ritzville, Wash., respectively; both were exposed to rain before collection]

ODWALV30 ODWALV3X ODWRZY10 LRIHAZ10 LRWRZZ2X

F~ 0.6 1.3 1.1 0.16 0.32 

Cl" 22 19 16 .5 .5 

P0£3 <4.7 <4.7 <4.7 <4.7 <4.7 

SOl2 73 60 18 .7 2.3 

NOg <-8 5.5 2.9 <.8 .9

Total <101 < 91 <43 <6.9 <8.7

Ca++ 60 55 19 6 3.5 

Mg++ 10 9 5 2.5 .8

Na+ 22 20 15 3.9 3.5

K+ 2.9 2.7 1.4 .8 <.3

Mn++ .7 .7 .3 .1 .03 

Fe++ <.4 <.4 <.4 .4 <.4 

Si4+ 4.3 4.3 1.4 2.8 2.8 

A1 3+ <1.1 <1.1 <1.1 <1.1 <1-1

Total <101 <93 <44 <1R <12
LEACHATE CHEMISTRY OF ASH 43

equivalents that would have been available to the water 

leach treatment. The preceding lines of evidence indicate that the sources of solute in the water leach and 

the rain leach are principally surficial deposits of readily soluble salt materials rather than primary igneous 

grains.

The relationships between electrically charged species 

in the acid leach solution are different from those in the 

water leach solution. Table 20 gives electrical balances 

in acid leach treatment solute for the same five samples 

for which water leach electrical balance data were presented in table 19. Table 20 also presents information

TABLE 20. Electrical balances of onion, cation, and proton equivalents in 0.01 F H^SO4 acid leach solutes from selected ash samples

[Data in milliequivalents per 10s g ash. Values in parentheses are for HNO3 leach treatment. Leaders ( ), no value was measured because of interference from the anion in leaching 

acid. Anion totals are approximate because SO'2 values from corresponding HNO3 leach were substituted and used in addition; similarly, NO* values from H2SO4 treatment were 

used to compute sums of anions for HNO3 acid leach. ODWALV30 and ODWALV3X are analytical replicate splits from Almira, Wash. ODWRZY10 is from Ritzville, Wash. These 

three samples were collected before exposure to rain. LRIHAZIO and LRWRZZ2X are from Harrison, Idaho, and Ritzville, Wash., respectively; both were exposed to rain before collection]

ODWALV30

F"

Cl~

POj3

so^2

N03

Total 

4.9

26

43

1.8

<161

(4.1)

(25)

(38)

(85)

( )

«153)

ODWALV3X

4.4

24

43

1.6

148

(4.2)

(22)

(38)

(75)

(~ )

«140)

ODWRZY10

2.5

21

28

1.0

<78

(2.4)

(19)

(13)

(25)

( )

«60)

LRIHAZIO

1.9 (1.7)

.2 (0.8)

24 (15)

 (10)

<.8 ( )

<37 «28)

LRWRZZ2X

2.2 (2.1)

1.3 (1.1)

28 (18)

 (8.3)

<.8 ( )

<41 «30)

Ca1

MgH 

NaH 

K+

Mn* 

Fe"* 

Si

Al

4+ 

3+

Total 

150

41

26

14

2.9

28

43

67

<372

135

39

23

13

2.8

27

43

63

<346

65

22

21

7.2

1.2

14

26

44

45

16

7.0

5.4

.6

>200

13

23

39

149

50

19

8.7

5.9

.8

15

26

44

>169

Difference between 

total cations and 

total anions 

Initial pH of solution 

(measured "blank" pH; 

0.009 M H2 S04 ) 

Final pH of solution 

( me as ur ed ) 

Protons consumed 

(calculated from 

measured pH values) 

211

2.06

2.82

98

Difference between 

non-salt-associated 

cations released 

and protons consumed- 113

Acid-associated anions

(calculated) 189

198

2.06

2.45

70

128

189

122

2.06

2.29

56

66

189

112

2.06

2.29

56

56

189

128

2.06

2.30

56

72

189
44 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

on the contribution of protons to the ionic electrical 

charge balance. This information is needed because 

there is a much greater abundance of protons (or 

hydronium ions) in solution at the lower pH values of 

the acid leach solution than at the near-neutral pH of 

the water leach solution, and the quantities of electrical 

charge associated with changes in proton concentration 

in the acid leach solution before and after treatment of 

the ash are considerable. Therefore, we included in table 

20 information on the contribution of protons to the 

ionic electrical charge balance.

The acid leach treatment yielded a large excess of 

positive charge from the cations Ca++, K+, Mg++, 

Na+, Mn++, Fe++, A13+, and Si4+ over the negative 

charge from the anions SO42, Cl~, PO43 , F~, and NO§. 

Both Mn and Fe ions are considered to have a formal 

charge of (II) because they are more commonly present 

in the reduced state in igneous-rock minerals. Silicon 

is included with the cationic species in these calculations 

because it is likely to be present in the solute as silicic 

acid (H4SiO4 °), an uncharged species, thereby consuming hydronium ions and affecting the pH. Aluminum 

would most likely exist as Al+3 at such acidic pH 

values. Nitric acid leaches were done on a few samples, 

in addition to the sulfuric acid leaches done on the larger 

number of samples, in order to get information on the 

amounts of SO42 removed from the ash under similar 

pH conditions in strong-acid solution.

The data of table 20 show that numbers of electrical 

equivalents of cations in solute typically exceed those 

of anions by about two and a half times, and that the 

hydronium ions consumed (determined from change in 

measured solution pH) typically account for only about 

half of that imbalance. However, the uncertainty in the 

results of table 20 is great because of uncertainty in the 

behavior, speciation, and charge of many species in the 

solutions. First, the number of equivalents of hydronium ions consumed were determined from measured 

pH values and converted to a per-gram-of-ash basis; if 

a calculated initial pH had been used, based on acid concentration and on the published dissociation constant 

for the second proton of H2SO4, hydronium ion consumption would have appeared to more closely bridge 

the excess of cation equivalents over anion equivalents. 

Also, the electrical sums for cations and anions were 

calculated without regard to speciation, and our assignment of the formal charge for an ion may be incorrect. 

With respect to the formal charge that we have attributed to the species listed in the tables, we do not 

mean to insist on the physical reality of these particular 

species, but rather to suggest a charge corresponding 

to the number of hydronium ions most probably consumed in ion-exchange reactions (or, in the case of silica, 

complexation reactions).

The relationships among equivalents of cations, 

anions, and hydronium ions moving into or out of solution during the acid leaching process suggest extensive 

replacement of cations on primary igneous mineral surfaces by hydronium ions of the acid leach solution. Such 

dissolution of many or most mineral phases contrasts 

with the apparent congruent dissolution of the readily 

soluble surficial material, which yields cations and 

anions to deionized water leach solution in electrically 

equivalent amounts. White and Claasen (1980) confirmed that, at a pH similar to the acid leach treatment 

in the present work, displacement of cations from 

rhyolitic glass is largely done by the protons in the 

leaching acid.

SIGNIFICANT CORRELATIONS BETWEEN CATIONS AND 

ANIONS IN THE LEACHATE

Results of this study indicate that there may be a 

direct association of Na with Cl in the readily watersoluble material that coats ash particles, and an association of both alkali and alkaline earth metals, as well as 

others, with SO4. Table 21 gives a correlation matrix 

for species in water leachates for a group of 13 samples 

collected before exposure to rain. The critical values are

TABLE 21. Correlation matrix for species measured in water leach

treatment

[Correlation coefficients were determined for 13 ash samples collected before exposure to 

rain from Washington, Idaho, and Montana. No analytical duplicates or Almira, Wash., 

time-sequence samples were included. Only those species whose leach-solution concentrations were above analytical detection limit for all samples are included in table, unless 

otherwise noted: in the cases of the Si and La analyses, two individual samples registering below the instrumental detection limit were assigned values 0.7 times the detection limit. Underlined correlation coefficients are significant at worst at the 5 percent 

confidence level. Cation values were determined by inductively coupled plasma spectroscopy; anion values were determined by ion chromatography]

Ca

K

Li

MS

Mn

Na

Si

Sr

4

Ca K Li Mg Mn Na Si 

1.00 0.93 0.55 0.90 0.77 0.62 0.48

 1.00 .51 .97 .86 .72 .37

 1.00 .52 .23 .38 .18

__ LOO .88 .83 .23

__ LOO .81 .07

 _- __ -_ __ LOO -.09

__ LOO

Sr 

0.97

.90

.52

.91

.83

.75

.33

1.00

Cl 

0.33

.43

.67

.57

.57

.90

-.27

.50

1.00

F 

0.20

.25

-.09

.38

.42

.58

-.14

9Q

.41

1.00

so4

0.97

.91

.49

.86

.79

.56

.42

.95

.25

.13

1.00
LEACHATE CHEMISTRY OF ASH 45

0.55 at the 5 percent confidence level, and 0.68 at the 

1 percent confidence level. As may be seen in the table, 

only Na strongly correlates with Cl, whereas Ca, Sr, K, 

Mg, and Mn strongly correlate with SO4. Many metals 

strongly correlate with each other. These results are 

similar to those of Smith, Zielinski, and Taylor (1982), 

but contrast some with the suggestion of Taylor and 

Lichte (1980) that there are two classes of salts, alkali 

(plus ammonium) chlorides and alkaline earth sulfates, 

the former being the more soluble. The lack of significant correlation between anions SO4 and Cl found by 

us contrasts with the highly significant correlation for 

this pair found by Smith, Zielinski, and Taylor (1982).

In the water leach solute, there is no significant correlation with F for any of the metals listed above.

Table 22 gives the correlation matrix for species in 

the acid leach solution. Many metals in the acid 

leachates strongly correlate with PO4 and with each 

other. Na and Cl again strongly correlate. SO4 is not 

included in this matrix because H2SO4 was used as the 

leaching acid. No species correlate strongly with F (except Mn with a correlation coefficient of 0.71). Correlations of Cu with other species are in a sense opposite 

to those observed for most metals.

From the correlation matrices for species in the 

water and acid leach solutes, some associations may

TABLE 22. Correlation matrix for species measured in acid leach treatment

(Correlation coefficients were determined for 13 ash samples collected before exposure to rain from Washington, Idaho, and Montana. No analytical duplicates or Almira, Wash., timesequence samples were included. Only those species whose leach-solution concentrations were above analytical detection limit for all samples are included in table, unless otherwise 

noted: in the case of the Li analyses, one individual sample registering below the instrumental detection limit was assigned a value 0.7 times the detection limit. Underlined correlation coefficients are significant at 5 percent confidence level. Cation values were determined by inductively coupled plasma spectroscopy; anion values were determined by ion 

chroma tography]

Al

Ca

Co

Cu

Fe

K

Li

Mg

Mn

iNa

Si

Sr

V

Y

*?-*

n

on .

Al Ca Co Cu Fe K Li Mg Mn Na Si Sr 

1.00 0.93 0.65 -0.19 0.87 0.93 0.59 0.94 0.89 0.07 0.94 0.86

 1.00 .40 -.15 .83 .87 .54 .88 .91 .25 .93 .96

-- 1.00 -.24 .71 .76 .52 .74 .58 -.36 .57 .27

 1.00 -.35 -.20 -.12 -.22 -.02 .49 -.28 -.03

__ __ __ LOO .96 .46 .96 .92 -.06 .90 .73

__ __ __ __ __ LOO .63 1.00 .95 .06 .91 .79

 1.00 .63 .54 .33 .53 .60

__ LOO .95 .06 .92 ,81

__ _ _ _ i nn o ^ P.O. Q P.

 LOO -.02 .44

I

nn Q &

_ _ _ _ _ _ _ _ _ _ _ i nn

V 

0.94

.85

.71

-.27

.79

.86

a o

Qd

.76

no

o 7

. / j

1.00

Y 

0.95

.93

.61

-.16

.81

.89

a o

P.Q

0 C

.05

.90

Q IT

.96

1.00

Zn 

0.58

.69

.18

-.15

.65

.59

. Zj

.60

a o

. UZ

7 o

.69

/ o .43

 3 J

1.00

Cl 

0.18

.27

-.13

.64

.06

.22

/ i .42

. zz

 j /

Q a

.12

.47

-.02

.12

.21

1.00

F 

0.55

.59

.33

.27

.55

.58

. zu

.60

.71

.29

.46

a o

.40

.51

.32

.33

1.00

P04 

0.89

.89

.57

-.19

.77

.85

a o

Q c

on

.07

o a

QO

.92

.94

.53

i ft

. 44H- H1 _nn
46 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

be inferred. Na and Cl correlate strongly in both leach 

treatments, suggesting presence of NaCl as a discrete 

substance. Ca, K, Mg, Mn, and Sr all have highly significant correlation coefficients with SO4 in the water 

leach, indicating the presence of sulfate salts. These ion 

associations are consistent with the presence of 

minerals detected in posteruption alteration products 

by Dethier and others (1981). Grains of salt identified 

as NaCl and CaSO4, as well as some other simple salts, 

have been identified on grains of ash from other eruptions (Rose and others, 1973,1980; Smith, Zielinski, and 

others, 1982), but Smith, Zielinski, and Taylor (1982) 

did not report discrete salt crystals on Mount St. Helens 

ash. Al, Ca, K, Mg, Mn, Si, Sr, V, and Y all have correlation coefficients greater than or equal to 0.80 with 

PO4 in the acid leach. Phosphate salts would be nearly insoluble in water but could be expected to be extensively dissolved at lower pH values. It is uncertain 

whether the metal-anion associations indicate the 

presence of discrete salts, complex mixtures of salts, 

or amorphous residues.

Ca/Sr RATIOS IN SOLUTES

The Ca/Sr ratios for whole ash, water leach solute, and 

acid leach solute are distinct, being lowest for whole ash 

and highest for acid leach solute. The data are presented 

in table 23. For samples collected before rainfall and 

before significant wind winnowing on the ground, there 

is no overlap in values for the sets of ratios for the three 

types of material. The three-fold-larger values of water 

leachate Ca/Sr ratios compared to whole-ash Ca/Sr 

ratios indicate that a separate and relatively more Carich reservoir of material is available to form the solute. 

The still larger Ca/Sr values for the acid leach solute 

indicate that there is a strongly selective removal of Ca, 

relative to Sr, by proton displacement (ion-exchange 

reactions) at grain surfaces. The dispersions in the sets 

of Ca/Sr ratios for whole ash, water leachate, and acid 

leachate are not great; the slightly greater dispersion 

in the leachate ratio sets is no more than would be expected from the poorer precision (fewer significant 

figures) of their concentration data. Also because of 

poorer precision associated with small concentration 

values, there is slightly greater dispersion in the data 

sets for post-rain samples than for pre-rain samples. The 

small magnitudes of the dispersions indicate that the 

source materials for both the water leach and acid leach 

solutes are homogeneous and consistent in composition, 

almost as much as the whole ash itself.

The lower section of table 23 is presented to remind 

the reader of the relative masses of the three types of 

material: water leach solute represents about 0.1-0.2

TABLE 23. Ca/Sr ratios in solutes, and total amounts of ash removed 

by leach treatments

[Amounts of ash removed by leach treatments are expressed as ppm of whole ash, and were 

calculated by summing amounts of five anions (Cl", F", NO", PO~3, SO~ ) and nine 

cations (Na+, K+, Mg++, Ca++, Ba++, A13+, Fe++, Mn++, Si4+) from solutes; 

values for SO" were estimated from results of a parallel acid leach treatment using 

HNO,. n, number of samples analyzed]

Ca/Sr ratios in solutes

Pre-rain samples Post-rain samples

(n=18) (n=8)

Mean Range Standard Mean ^ Standard

deviation deviation

Whole ash 74.2 68-78 2.6 74.4 67-80 3.8 

Water leach

solute 252 200-289 28 164 MOO-200 44 

Acid leach

solute 326 290-360 28 348 162-471 94

Total amounts of ash removed (ppm) by leach 

treatments (calculated)

Pre-rain samples 

(n=18)

Mean Mean

Post-rain samples 

(n=8)

Standard Range deviation

Water leach

treatment- 1,600 

Acid leach

treatment- 6,700

480 370-860 180 

4,150 3,400-6,050 800

percent and acid leach solute about 0.5-1 percent of 

whole ash, for pre-rain samples.

AMOUNTS OF SPECIES YIELDED TO MILD AND HARSH 

LEACHING TREATMENTS

Those elements that most nearly yield equal amounts 

to the deionized water and acid treatments (fig. 9) probably have a major fraction of their leachable totals in 

the form of water-soluble surficial coatings. Elements 

that best meet this criterion are the alkali and alkaline 

earth metals, the transition metals Ni, Co, V, and Mn, 

and the anions Cl~ and SO42. Solubility limitations may 

be the controlling factor for some species concentrations. Smith, Zielinski, and Taylor (1982) ran successive 

4:1 liquid-to-ash ratio (by weight) leaches on fresh 

Mount St. Helens ash with an initial deionized water 

leach followed by an acid leach of dilute HC1 (pH 

3.5-4.0). They found the same species (SO42, Ca, Cl~, 

Na, Mg) to be yielded in greatest abundance to both the 

initial deionized water and the subsequent acid leachate, 

with the acid leach solute concentrations equal to about 

one-third those of the water leach.

Species not associated with common water-soluble 

salts and not detected in the present study in the water 

leach solution, such as PO43, Al, and Fe, are prominent
LEACHATE CHEMISTRY OF ASH 47

species in the acid leach solute. By the stoichiometry 

of any suite of igneous phases expected to act as sources 

of solute, there is in the acid leach solute a deficiency 

of Si relative to the major cations Ca, Mg, Na, and K, 

whether or not the contribution of a balanced suite of 

cations and anions from soluble surface salts is included in the calculation. It should be noted that oxides, 

sulfides, and phosphates might exhibit increased 

solubility in acidic solutions, but would be expected to 

exhibit approximately congruent dissolution. The data 

suggest the presence of a discrete phase in the ash that 

is less water soluble than other materials which are well 

represented in the water leach solute.

CONTRIBUTION TO SOLUTE BY 

PRIMARY IGNEOUS GRAINS

The distribution of all elements among the various 

species and sizes of grains in the ash is not well known. 

Ni, Mn, and Co, removed by water leach in amounts 

representing about 2-5 percent of their whole-ash totals, 

are expected to be concentrated in the opaque and dark 

minerals of the ash, which are susceptible to rapid 

breakdown by weathering; however, these elements 

may also be present in surficial coatings.

Some ash particles are older altered grains of glass, 

minerals, and lithic fragments, and any of these may 

contribute to leach solutes in distinctive ways. Such 

materials, quarried from the throat of Mount St. Helens 

during eruption, may or may not be more easily attacked by solutions than would grains of many fresh 

primary species, and they may provide solute material 

at an unknown rate.

In mixed mineral systems, the kinetic rates of dissolution of individual constituent cations are not simple 

combinations of the rates of cation dissolution from the 

individual minerals involved. Differences in the identities and grain sizes of the minerals in the mix may control variations in the fractional removal of cations from 

the outer atomic layers of the mineral grains in the 

rock-solution system.

Many authors have recently discussed the mechanisms and kinetics of uptake of material by solutions 

from minerals, glasses, rocks, and soils (Lepel and 

others, 1978; Maenhaut and others, 1979; Naughton and 

others, 1974; Smith and others, 1981). Generally, in the 

earliest stage of dissolution, cations may be displaced 

by hydronium ions in the solution. Over much longer 

times, true congruent dissolution of minerals may occur. The amount of material in solution may be a proportion of the square root of time of exposure (parabolic 

dissolution curve); with such a relationship there may 

appear to be an initial period of rapid uptake (possibly

due to very fine grain size of some particles) by the solution, followed by a later period of slower uptake during 

which the relation between time and amount of solute 

may appear to be nearly linear. The effects associated 

with the dissolution of feldspars in low-pH solutions, 

described by Busenberg and Clemency (1976), include 

relatively equal release of Na and Ca, moderate release 

of Al, and copious release of Si; these effects were not 

approximated during the acid leach treatment of Mount 

St. Helens ash in the present study. From our Mount 

St. Helens data, about two to four times more Ca than 

Na seems to be released, and large amounts of both Al 

and Si are released. However, the feldspar composition 

and mean grain size of the ash are different between the 

present study and that of Busenberg and Clemency. 

It is worthy of consideration that important sources 

of many elements in the agitated leach extractions of 

the present study, and the column leach extractions of 

Taylor and Lichte (1980), may be the abundant, 

mineralogically unidentified ultrafine particles that are 

observed clinging tenaciously to the surfaces of larger 

grains in scanning electron microscope photographs of 

the Mount St. Helens ash. Most of these are probably 

fine fragments of minerals or glass rather than particles 

of the highly soluble surficial material. As proposed by 

Holdren and Berner (1979) and Berner and Holdren 

(1979), these ultrafine grains and "* * * sites of excess 

surface energy, such as at dislocations or similar crystal 

defects * * *" could be expected to supply to solution 

greater amounts of the elements than would larger 

grains, and could thus be responsible for the initial 

parabolic dissolution observed by many researchers 

over exposure times approximately the same as those 

of the present study.

VARIATION IN AMOUNT OF THE 

SOLUBLE MATERIAL

The variation in chemical and mineralogic composition of samples of whole ash and the relationship of that 

variation to time of fall and distance from source are 

discussed in Chapter A of this volume. (See also Taylor 

and Lichte, 1980; and Sarna-Wojcicki, Meyer, and 

others, 1981.) Basically, there is one end-member compositional type of Mount St. Helens ash that is dark 

colored, with abundant opaque and dark minerals and 

calcic plagioclase, phases that taken together are 

relatively rich in Ca, Mg, Fe, Sr, Mn, Ni, Co, and V. This 

dark-colored ash is abundant in the ash that fell early 

from the suspended plume or close to Mount St. Helens, 

although there appears to be considerable local variation. The other end-member compositional type is light 

colored, and is characterized by abundant glass and
48 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

sodic plagioclase, phases rich in Si, Li, Na, and K. This 

light-colored ash is more abundant in ash that fell later 

or at greater distances from the volcano, although for 

these species also the relation between composition and 

distance from source is only general.

Various lines of evidence (composition of water leach 

solute, composition of material removed by rain, consistency in amounts of elements removed by procedures 

using varying water-to-ash ratios, and details of electrical ion balance) make it clear that a quantity of readily soluble material is present as a minor but distinct 

component of the ash. Ca, Na, K, Mg, Si, and Mn, in 

decreasing order of abundance, form the greatest bulk 

of cationic species in this soluble material. Their proportions in the solute remain fairly constant for all 

samples. However, amounts of total solute removed by 

a given leach treatment vary considerably.

The question arises of whether there is a simple relationship between amount of soluble material available 

to be dissolved from the ash, and compositional type 

of the ash. Observations on this possible relationship 

can best be made by determining statistical correlations

between (1) amount of selected elements removed in 

leach treatments and (2) concentrations of the elements 

that serve to characterize the compositional type of the 

whole ash. Table 24 presents correlation coefficients between amounts of various species removed by leach treatments from pre-rain samples, and concentrations of three 

key species in whole ash. Calcium was chosen to characterize the dark-colored ash, which is rich in ferromagnesian minerals and calcic plagioclase; Na and Si were 

chosen to characterize the light-colored ash, which is rich 

in glass and sodic plagioclase. Several species show highly 

significant correlation coefficients between mass removed by both water and acid leach treatments and 

whole-ash Ca, Na, and Si. The generally strongly positive 

correlation coefficients between whole-ash Ca and solute 

species, and the negative coefficients relating Na and Si 

to solute species, indicate that the dark-colored ash, containing opaque and dark minerals and calcic plagioclase, 

yields more of most constituents of the soluble material 

than the light-colored ash, which contains sodic 

plagioclase and glass. Solute Cu is associated with the 

more silicic type of ash and is an exception.

TABLE 24. Correlations between whole-ash calcium, sodium, and silicon, and species removed by water and acid leach treatments

[Correlation coefficients were determined for 13 ash samples from Washington, Idaho, and Montana, and for five time-sequence samples from Almira, Wash., all collected before being 

rained on. No analytical duplicates were included. Only those leachate species whose leach-solution concentrations were above the analytical detection limit for all samples are 

included in table, unless otherwise noted: one individual value below the instrumental detection limit for the Li acid leachate analyses, and two values for the Li and Si water 

leachate analyses, were assigned values 0.7 times the respective detection limits. Underlined correlation coefficients are significant at 5 percent confidence level. Cation leachate 

values were determined by inductively coupled plasma spectroscopy; anion leachate values were determined by ion chromatography; whole-ash values were determined by X-ray 

fluorescence]

Washington, Idaho, and Montana samples Almira time-sequence samples

Water 

leach 

species

Ca 

K 

Li

Mg 

Mn

Na 

Si 

Sr

Cl 

F

so 4

Wholeash Ca 

Wholeash Na 

Wholeash Si

Wholeash 

Ca

0.83

.79

.44 

.66

.53

.18 

.65

.69

-.14 

-.11 

.85

1.00

 -

Wholeash

Na

-0.64

-.58

-.49 

-.49 

-.22

-.10 

-.76

-.50

.16 

-.05 

-.57

-.72

1.00

 _

Wholeash 

Si

-0.91

-.88

-.52 

-.82

-.66

-.41 

-.52 

-.81

-.07 

-.14 

-.90

-.94

.68

1.00

Acid 

leach 

species

Al 

Ca 

Co 

Cu 

Fe

K

Li 

Mg 

Mn 

Na

Si 

Sr

V 

Y 

Zn

Cl

F

PO A

Wholeash 

Ca

0.95

.90

.67 

-.26 

.89

.94

.57

.94

.88

.06 

.88

.80

.91

.94

.47

.12 

.52 

.89

Wholeash

Na

-0.74

-.79

-.43 

.44 

-.82

-.77

-.43 

-.76

-.77

-.07 

-.83

-.70

-.70

-.69

-.72

-.04 

-.23 

-.66

Wholeash 

Si

-0.91

-.90

-.48 

.21 

-.79

-.87

-.65

-.88

-.84

-.30 

-.84

-.86

-.82

-.88

-.45

-.32 

-.45 

-.83

Acid 

leach 

species

Al 

Ca 

Co 

Cu 

Fe

K 

Li

Mg 

Mn 

Na

Si 

Sr 

V 

Y 

Zn

Cl

F

PO &

Wholeash 

Ca

0.19 

.62 

.79 

-.96

.94

.88

.71 

.90

.76 

-.12

.75 

.53 

.69 

.83 

.74

.31 

-.37 

.56

Wholeash

Na

-0.27 

-.68 

-.50 

.91

-.87

-.82 

-.56 

-.84 

-.77 

-.02

-.68 

-.59 

-.62 

-.78 

-.78

-.39 

.24 

-.65

Wholeash 

Si

-0.30 

-.71 

-.65 

.95

-.95

-.90

-.69 

-.92

-.83 

-.02

-.78 

-.63 

-.72 

-.86 

-.82

-.43 

.30 

-.66
LEACHATE CHEMISTRY OF ASH 49

Table 25 presents correlation coefficients between the 

amount of each element removed by water or acid leach 

treatments and its own whole-ash concentration. The 

data show that the relationship defined above, between 

amount of soluble material and whole-ash composition, 

holds for both water and acid leach treatments. In the 

water leach treatment only those elements that are 

more abundant in the dark-colored ash (Ca, Mg, Sr, Mn) 

significantly correlate positively between amount in 

fresh-ash water leach solute and whole-ash concentration; those that are less abundant in the dark-colored 

ash (K, Na, Si, Li) either correlate negatively or show 

no significant correlation. In the acid leach treatment, 

the same relationships hold for the two groups of four 

elements; the additional elements Al, Fe, V, Y, and Zn, 

not successfully detected in the water leach treatment, 

are positively correlated with their own whole-ash 

concentrations.

OTHER EVIDENCE ON SOURCE MATERIAL FOR 

ACID LEACH SOLUTE

The sources of solute to acid leach treatment appear 

to be: (1) the same salts available to the water leach 

treatment (largely Cl~ and SO^2 salts); plus (2) other 

less easily soluble salts such as PO^3 and possibly OH~ 

and O~2 salts or amorphous material; and (3) protondisplaced surficial cations from the minerals 

themselves. The segregation of elements into two 

distinct groups in figure 9 may be used in conjunction 

with the acid and water correlation coefficients of table 

25 and the electrical ion balance data of table 20 to give 

complementary information on the nature of sources of 

acid leach solute. The group of elements that is removed 

much better by acid than by water (the "high" part of 

the plot of fig. 9) includes Fe, Al, Y, and Zn; this suggests that a massive source of solute not available to

TABLE 25. Correlations between removal by water or acid leach treatments and whole-ash content for each chemical species

[Correlations were determined on 13 ash samples (unless otherwise noted by dagger (t), which indicates five samples) from Washington, Idaho, and Montana and on five time-sequence 

ash samples from Almira, Wash.; all were collected before being rained on. No analytical duplicates were included. Only those leachate species whose leach-solution concentrations 

were above the analytical detection limit for all samples are included in the table, unless otherwise noted: individual leachate samples registering below the instrumental detection 

limit, two each for both Li and Si for water leach analysis, and one sample for Li for acid leach analysis, were assigned values 0.7 times the respective detection limits. Underlined 

correlation coefficients are significant at the 5 percent confidence level. Cation leachate values and some whole-ash values were determined by inductively coupled plasma spectroscopy; other whole-ash values were determined by X-ray fluorescence; anion leachate values were determined by ion chromatography]

Washington, Idaho, and Montana samples Almira time-sequence samples

Ranked 

species

Mg 

Ca

Fe

Sr

Al

Zn

V

Y 

Mn

Co

Cu 

Na 

Li

Si 

K

Cl*

F 1"

Acid leach 

correlation 

coefficient

0.93

.90

.89

.87

.86

.86

.67

.63

.62

.50

.41

-.07 

-.47

-.84

-.89

.79 

.15

-.19

Ranked 

species

Ca

Mg

Mn

Sr

Li

Na

Si

K

soA T

F*

Water leach 

correlation 

coefficient

0.83

.74

.70

.67

-.02

-.10

-.52

-.82

.92 

.79 

.78

Ranked 

species

Fe 

Mg

V

Mn

Co

Zn

Ca

Cu

Sr

Y

Na 

Al 

Li

Si 

K

F 

Cl

PO,

Acid leach 

correlation 

coefficient

0.96

.92

.77

.72

.68

.66

.62

.51 

.47

.25

-.02 

-.21 

-.53

-.78 

-.80

.27 

.14

-.09

Ranked 

species

Mg 

Ca

Sr

Mn

Li

K

Na

so4

F 

Cl

Water leach 

correlation 

coefficient

0.64 

.58

.46

.35

-.68

-.46

-.35

.99

.74 

-.01
50 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

water leach becomes available to displacement by protons during the acid leach treatment. An alternate 

hypothesis would be that there is an additional reservoir of somewhat more resistant acid-soluble surficial 

salt deposits. In contrast, the elements Ni, V, and Co, 

which appear in the "low, flat" part of the plot of figure 

9, are among the group of elements removed only 

moderately more successfully by acid than by water. 

Water leach solute data on Ni, V, and Co were not complete enough to allow calculation of correlation coefficients; but from figure 9 it can be inferred that mineral 

sources of these elements for acid leach treatment are 

probably minor and that they are largely available to 

both kinds of treatments as more soluble and less soluble surficial salts.

The acid leach coefficients are generally somewhat 

larger in magnitude than those for water leach, suggesting the following: (1) to the extent that additional 

salts, rather than the surfaces of the minerals 

themselves, are the source of acid leach solute, the salts 

are probably physically associated with mineral grains 

containing a large amount of the same elements, and 

(2) the salt deposits are formed by acid attack on individual grains during or shortly after air transport. 

This is in opposition to the alternative possibility of indiscriminate condensation of element-rich aerosols on 

all types of ash particles during transport from the vent.

TRENDS IN GROUPS OF ASH SAMPLES

SYSTEMATIC AND RANDOM CHANGES IN LEACHATE

CONCENTRATIONS IN THE ALMIRA, WASH.,

TIME-SEQUENCE SAMPLES

Between samples within certain sample groups, there 

appear to be definite differences in the amount of some 

elements released to the leach treatments. This is best 

seen in the time-sequence samples from Almira, where 

there may be systematic variations in species concentrations through time of fall. Figure 10 shows variations 

in species concentrations for the water leach. For several 

leachate species, there is a striking concentration 

decrease from the sample representing the final collection period at the Almira site; the leachate concentrations are largest from samples representing the middle 

period (from 4 to 6 p.m. PDT) of ashfall collection. 

Silicon concentration, however, remains constant 

throughout the time span. Figure 11 shows similar 

trends for the acid leach. Acid leach Cu (not detected 

in water leach solute) displays behavior through time 

of fall that is opposite to that of other solute species. 

Also, F~ is abundant in solute from the initial sample. 

The systematic changes may indicate differences in the

nature and abundance of the materials that hold and 

release soluble species, and these differences may be 

associated with time of fall, changes in the composition 

of the eruptive gases, changes in temperature and 

pressure, differing exposure times of the samples before 

collection, grain size (surface area), or identity of mineral 

species (or position in mineral solid solution series). A 

systematic relationship to time of production from the 

volcano source, rather than merely an empirical relationship to time of precipitation from the overhead plume, 

must be regarded as a possibility for further research.

DIFFERING AMOUNTS OF MATERIAL YIELDED TO LEACHING 

SOLUTIONS BY GROUPS OF ASH SAMPLES

Samples collected after exposure to rain yielded less 

solute to acid leach treatment than expected if it is 

assumed that rain should remove the same amount of 

material as the 14:1 (by weight) water leach treatment. 

This may be explained through the widely reported 

observation (Leifer and others, 1981) that airborne or 

newly fallen ash bore liquid condensates of concentrated 

strong acid. Moderate wetting in the field (filling of the 

pore volume in the ash blanket, without flushing), as 

by light rain, could have exposed ash particles to extensive contact with solutions whose pH approached 

that of the acid leach treatment of the present study. 

Such exposure may have made available more material 

(to be removed later by heavier rain) than sudden 

flushing by a large volume of solution of near-neutral 

pH, such as in the water leach treatment of the present 

study. Such acid condensates may have evaporated 

before the fall of rain, leaving a residue of altered 

material on grain surfaces, to be flushed away later.

The greater yield to leaching solutions of the Almira 

samples, compared to other samples collected before exposure to rain, might be explained by similar considerations. The Almira samples were collected on plastic 

sheets, and sealed in jars only minutes or hours after 

fall. Other pre-rain samples were collected from various 

surfaces and had longer exposures to air. Contact with 

volatile acidic condensates during the time of confinement between collection and analysis could have made 

the Almira samples more susceptible to dissolution during leaching experiments. It may be observed that the 

last-collected Almira ash sample (ODWALV50) produced, for many chemical species, the lowest solute concentrations of any Almira sample. Because of the longer 

time span represented by this sample it was exposed 

to air several times longer than any other sample in the 

sequentially collected suite. However, the last-collected 

Almira sample also differs from the others in its wholeash chemistry; it also conforms differently than the
LEACHATE CHEMISTRY OF ASH 51

other Almira samples to the set of strong positive and 

negative correlations observed between amount of 

solute removed by leach treatments and whole-ash 

chemical composition for the larger group of all samples 

collected before exposure to rain.

5.6 

5.4 

5.2 

5.0 

4.8 

4.6

30

4.5 

4.3 

4.0

3.5

3.0 

2.8

120 

110 

100 

90 

80

1,200 

1,100 

1,000 

900 

800 

725

3,500 

2,750

2,000 

1 P

Whole-ash Ca

, 

I

Si

I ' 

 '

Sr

___ r J

_

Mg

-

Ca

 J -

. ^ I '

I

'

:

LI

. _ »*L___»

Na

- 

. ______ * _______ -

"

Cl

/ i

64.5 

64.2

63.6 

63.0 

62.4 

61.8 

61.2 

0.8 

0 6 

0.4 

0.2

19 

17 

15 

13

500 

470 

440 

410 

380

114 

110

100 

90

80 

76

790 

750 

700 

650

600 

580

m. 2 p.m. 3 p.m. 4 p.m. 5 p.m. 6 p.m. v V 8 a.m. 

MAY 18, 1980 MAY 19, 1980

FIGURE 10. Water leach concentrations (in ppm ash; whole-ash Ca 

and Si in weight percent) of solute species in samples collected 

through five abutting time increments at Almira, Wash. Arrows 

point to the appropriate concentration scale.

GRAIN SIZE OF THE ASH

Consideration of the varying average grain sizes of 

the ash samples in relation to amount and composition 

of leachates is complicated by the fact that the ash-fall

600

550 

500

470 

5.2

5.0

4.5

610

590

570

79

70 

61 

52

40

1,300

1,200

1 1 Kn

 ~~ ^

r Na

Zn

 __J !

_

Al

t '

L_J }___, 

-

, ____ J 

1

, p<V ^

_

1

_

- _ -i y

-

Cu

r ~~?

-

~

_______ Ff ______ -

C' -»"

. / . ,

3.6 

3.4 

3.2

3.0 

2.9

3,000

2,500 

2,100

6.5 

6.0 

5.5

5.0 

4.9

800 

750 

700

650 

630

onn

850 

800 

750 

~?nn

2 p.m. 3pm A p.m. 5 p.m. 6 p.m. 

MAY 18, 1980

8 a.m. 

MAY 19, 1980

FIGURE 11. Acid leach concentrations of solute species in samples 

collected through five abutting time increments at Almira, Wash. 

Arrows point to the appropriate concentration scale.
52 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

blanket is believed to be composed of discrete strata of 

variable relative thickness. The character and magnitudes of the component strata are discussed in detail 

by Sarna-Wojcicki, Shipley, and others (1981). Our ash 

samples represent vertical integrations of those strata, 

except for those from Almira and Missoula in which portions of the total thickness were sampled discretely. The 

basal "unit 1" of Sarna-Wojcicki, Shipley, and others 

(1981) is a thin, gray, silt-size ash; "unit 2," directly 

overlying unit 1, is also thin, and is a "salt and pepper," 

fine-sand-size ash composed of lithic and crystal 

fragments and fine pumice shards; "unit 3," directly 

overlying unit 2, is as much as 20 or more times thicker 

than units 1 or 2, and is a light-gray to tan, fine-sandto silt-size ash composed of pumice and glass shards, 

crystals, and minor lithic fragments. Only at those 

geographic locations where the ash-fall blanket 

stratigraphy has been mapped could the relative 

amounts of the different strata represented in our 

samples be well determined and well interpreted; this 

would be most reliable in the thick central area of the 

ash-fall blanket, partly because of the ease of mapping 

the thick blanket in that region and partly because unit 

3 increases its predominance over other units there. 

More detailed analysis of the data, and possibly more 

spatial grain size distribution information, would be required to determine whether there is any association 

between the larger observed yield of solute and the 

larger relative thickness of the finer grained unit 1 in 

ash close to the volcano. The same is true for the problem of determining the relationship between the relative 

amount of ferromagnesian constituents of the leachates 

and the relatively large amounts of dark units 1 and 2 

from samples collected close to the volcano.

RELATIONSHIP OF LEACHATES OF

MOUNT ST. HELENS ASH TO 

LEACHATES OF COMMON SOILS

COMPARISON OF AMOUNTS OF ELEMENTS

REMOVED FROM ASH AND AMOUNTS REMOVED FROM

COMMON SOILS, AND THE INTENSITY AND CAPACITY

PROPERTIES OF THE TWO MATERIALS

Despite the higher solution extract values for ash 

than for soils (table 17), there is an important and fundamental difference between the intensity and capacity properties of ash and soils. This difference is that 

solute concentrations through a series of extractions on 

the ash decrease greatly, whereas it has been well 

established for decades (Adams, 1971) that solute concentrations from sequential extractions of typical soils, 

irrespective of the nature of the leach treatment, change

only little. Table 26 presents measurements by Taylor 

and Lichte (1980) of concentrations of selected elements 

in three successive, 4-hour, single-pore-volume leaches 

of ash, and also compares these values to the average 

saturated-paste soil extract values of Bradford and 

others (1971). Ash leachate values obtained by the column method by Taylor and Lichte are presented in this 

table in spite of yielding, for many minor and trace 

elements, different values from those obtained by the 

14:1 extraction method of the present study. It is interesting to note that among the elements listed in table 

26 as having low concentrations in the ash leachates, 

there are some that are commonly thought of as being 

of "environmental concern" (Na, B, Ba, Mo); among 

those with high concentrations are some recognized as 

essential or beneficial to plant nutrition (K, Mg, Cu, Fe, 

Zn). A different impression is gotten from the data of 

table 17, in which leachate data from the present study 

and other ash leachate studies are compared to summarized leachate data for common soils. In table 17, in 

which the data are presented as whole-rock concentrations rather than as solution concentrations, the 

amounts of Na, Ba, and Mo released by ash are as large 

or larger than those released by soils. However, in 

evaluating the data on comparative amounts of metals 

released by ash and soils, the reader is cautioned to bear

TABLE 26. Successive pore-volume water leaches of ash compared

to water extracts of common soils 

[Value in parentheses is semiquantitative. Successive pore-volume leaches are from data of

Taylor and Lichte (1980) for ash from Spokane, Wash.; common soil extract values

are from Bradford and others (1971)

Element

#1

Successive porevolume leaches 

(mg/L)

#2

Common soil

extract mean

(ppm)

#3

High concentrations in ash leachates

Co 

Cu

Fe 

K

0.1 

.3 

.1 

(70)

0.011

.04

.03

0.003 

.02 

.2

0.06

.04

.05

20

Li

Mg

Mn

Zn

.6

109

22

.6

.14

20

3.8

.04

.05

6.7

1.2

.008

.11

38

.17

.07

Low concentrations in ash leachates

B

Ba

Mo

Na

V

0.8

.12

.02

559

<.001

0.4

.1

.01

115

<.001

0.08

.04

.02

43

.003

3

.26

.7

524

.07
LEACHATE CHEMISTRY OF ASH 53

in mind the importance of the units in which the data 

are presented, and the different metal-releasing 

behaviors of ash and soils in successive leach 

treatments.

CONTRASTS IN LEACHABLE CHEMISTRY OF ASH 

AND TYPICAL SOILS

The correlations between compositions of whole-ash 

samples and their leachates in this study are stronger 

than those reported throughout the literature for whole 

soils and their leachates (Severson and others, 1978). 

There is better precision between leachate analyses of 

splits of ash samples in the present study than between 

those of splits of soil samples reported in the literature. 

Also, there is rather good correspondence between 

results on ash samples leached using somewhat different methods (namely, the deionized water leach 

method of the present study done at a 14:1 waterrash 

ratio and the single-pore-volume deionized water leach 

of Taylor and Lichte, 1980), whereas different methods 

used for availability analyses of soils commonly yield 

different results (Jenne and Luoma, 1977; Mitchell, 

1972; Yagodin and Sobachkina, 1977). Most of these 

contrasts probably stem from the fact that the ash is 

a simpler material than most soils. The ash is largely 

composed of primary igneous materials (although 10 

percent or more of distal and 25 percent or more of proximal ash samples may be altered material), whereas soils 

consist of primary minerals, secondary minerals, clays, 

organic matter, and grain coatings composed of sesquioxides of transition and other metals. In many soils, 

a major fraction of the reservoir of elements available 

to leaching treatments (or even whole-soil elements) 

could be contained in any of these phases. Recently, 

there has been discussion of the possibility of complex 

redistributions of chemical species (extractable ions) 

taking place among the many soil constituents during 

the laboratory extraction procedures themselves 

(Rendell and Batley, 1980). Such redistributions may 

be similar to processes operating in the system of plant 

roots, soil components, and solutions in nature. Such 

complications are much less likely to be important in 

the case of the ash and the complex redistribution of 

the chemical species it would release.

CONCLUSIONS

1. Elements yielded by the ash to the two leaching 

treatments used in this study come from two 

distinct types of source material in the ash. The 

first source material, which yielded the bulk of

material removed by the near-neutral pH (water) 

leach treatment, is composed of salts or amorphous 

material and probably represents surficial coatings 

on the grains of the primary igneous species in the 

ash. Such material may be largely composed of 

alkali and alkaline earth metals, and Mn and Si, and 

the anions SO^2 and Cl~, with lesser amounts of F~ 

and NO§. The close electrical balance between cations and anions in the water leach solute implies 

congruent dissolution of ionic salt material. A PO^3 

salt phase, susceptible to dissolution only by the 

harsher acid treatment, may also be present.

The second source material is the primary igneous 

phases themselves, which largely through surficial 

cation-proton ion-exchange reactions yielded the 

bulk of the much larger amounts of material removed as solute by the low-pH (acid) leach treatment. In addition to the alkali and alkaline earth 

metals present in the water leach solute, large 

amounts of the mineral-forming species Fe, Al, and 

Si are present in the acid leach solute. In contrast 

to the water leach, no close electrical balance between cations and anions removed from the ash exists in the acid leach solute, confirming that 

surficial deposits of ionic salts are not the sole 

source of material removed by acid leach treatment. 

Cations in acid leach solute are present in different 

proportions from those in the grains themselves.

2. More generally, in both water and acid leach 

treatments, chemical species were removed from 

the ash in varying proportions of their whole-ash 

contents. Ni, Mn, and Co, and P, Cu, Y, La, and Mn 

were removed by water and acid leaches, respectively, to the greatest fractional extent. This is so in 

the water leach solute because the compositions of 

the surficial salt deposits are different from those 

of the grains of ash. In the acid leach it is so because 

some species were selectively removed during the 

cation-proton ion-exchange reactions that occurred 

on the surfaces of the various minerals. Larger absolute amounts of all elements were removed by 

acid leach than by water leach, but for some species 

the difference in removal by the two types of treatment was much greater than for others (50-500 

times more Cu, Fe, and Zn were removed by acid 

leach than by water leach, but only 2-5 times more 

Mn, K, Mg, Ca, and Sr). This is due to (1) the partitioning of elements between grains and surface 

coatings, and (2) certain minerals, with their distinctive compositions, being more susceptible to acid 

attack than others.

3. Strong positive and negative statistical correlations 

between concentrations of an element in whole ash 

and amounts of the same element in water leach
54 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

solute show that of the two end-member compositional types of ash, the dark-colored type (rich in 

opaque and dark minerals and calcic plagioclase 

and partly altered material, and poor in glass and 

sodic plagioclase) released a greater amount of 

material to leach treatment than did the lightcolored type. The contrast may be due to different 

eruption times and associated plume gas 

chemistries for the two types of ash, to different 

susceptibility to grain degradation while under attack by acid droplets shortly after eruption, or to 

other factors.

4. In nature, much of the material present as soluble 

surficial coatings was removed at the time of first 

contact of the ash-fall blanket with waters of nearneutral pH, such as rain. This was confirmed by 

laboratory measurements on samples from single 

sites, some collected before exposure to rain, some 

after. The excellent cation-anion electrical balance 

for material apparently removed by rain confirms 

the common-salt compositional nature of that 

material.

5. Single leach treatments of ash yielded larger solute 

concentrations of all species measured than would 

be yielded by soils. However, subsequent leaching 

of the ash yielded only much diminished solute concentrations, in contrast to natural soils that continue to release substantial quantities of solute to 

subsequent wettings.

6. There is a much better correspondence between 

whole-ash elemental concentrations and leachable 

concentrations, especially acid leach concentrations, than is ever the case for soils. This is probably a reflection of the absence from the ash of 

clays, organic matter, and oxide coatings.

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APPENDIXES C AND D
58 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

APPENDIX C. COMPLETE TABULATION OF ANALYTICAL RESULTS FOR LEACHATES

[Leachate determinations were done by inductively coupled plasma optical emission spectroscopy for non-anionic species and by ion chromatography for anionic species, after 14:1 watenash 

or 0.01 M HjSO, acid:ash leach treatments of 4 hours, with gentle agitation. The leachate analyses are described in Chapter B of this volume]

Coding key for eight-character sample identifiers for ash samples analyzed is as follows:

Character 1. 0="original," collected by on-site colleagues immediately after deposition 

L="later," collected by authors weeks after deposition.

Character 2. D=not rained on before collection ("dry")

R=exposed to rain before collection ("rain")

Character 3. Initial of State in which sample was collected: W=Washington, I=Idaho, C=Colorado, M=Montana, and K=Kentucky

Characters 4 and 5. City or town or other name for locality:

AL=Almira HE=Helena RL=Ralston

CA=Coeur d'Alene LE=Lewis town RR=Randle Ranger District

CO=Connell MC=Miles City RZ=Ritzville

CR=Columbia River MI=Missoula SG=Sprague

basin ML=Moses Lake SH=Mount St. Helens

DE=Denver PL=Plummer SM=St. Maries

EL=Ellensburg RA=Rest area, 18 SP=Spokane

EM=Emida miles east of UC=Union City

GL=Glasgow Ellensburg YK=Yakima

HA=Harrison RI=Richland YV=Yakima Valley

Character 6. Collector of sample:

B=Mr. Burton M=Dan Mueller V=Homer Evers

C=Russ Collett P=Paul Hammond W=Willard Henning

E=EUen Hall Q=Air Qual. Bur. X=Hansford Shacklette

H=Ed Heffern R=Ken Cochran Y=Donnie Rambo

K=Thor Kiilsgaard S=Wyatt Silker Z=Kathleen Smith

L=Steve Luthy T=Anita Tarbert

Character 7. Sample number of sub-location number, if more than one sample was collected by a single collector at the site identified by 

characters 4, 5, and 6.

Character 8. An "x" indicates that sample is one member of a duplicate pair (analytical split). In each duplicate pair one sample is labelled 

"x", the other "o". All samples not split for duplicate analyses are labelled "o".
LEACHATE CHEMISTRY OF ASH 

WATER LEACHATE ANIONS

[Values in ppm]

59

Sample

LRWSHP10

LRWSHP20

LRWSHP30

LRWSHP40

LRWSHP50

LRWSHP60

LRWSHP70

LRWSHP80

LRWSHP90

LFWSHPOO

ODWRRR10

ODWRRR1X

ODWRRR20

ODWRRR2X

ODWRRR30

ORWRRR40

ORWRRR50

LRWYVZ10

LRWYVZ20

LRWRAZ10

LRWRAZ20

LRWELZ10

LRWYKZ50

LRWCRZ10

LRWCRZ20

ODWRIS10

LRWMLZ10

LRWMLZ1X

LRWMLZ20

LRWMLZ2X

LRWMLZ30

LRWMLZ40

ODWALV10

ODWALV20

Cl

78

980

320

400

350

200

170

21

5

12

430

520

720

730

430

5

41

2

3

13

7

46

97

12

13

290

36

36

30

43

24

8

610

610

F

4

7

6

6

6

6

6

2

4

3

8

13

9

9

11

4

4

3

3

7

4

6

9

5

5

8

6

5

6

6

7

5

10

10

N03

<50

50

<50

50

69

<50

<50

<50

50

<50

<50

60

63

53

56

63

<50

<50

53

51

93

74

130

<50

<50

150

<50

<50

<50

68

77

76

70

<50

P04

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

so4

310

870

340

390

400

280

220

63

35

7

2,100

2,100

2,700

2,800

2,800

39

91

56

100

120

50

550

160

74

97

980

120

110

98

121

170

45

2,800

2,700

Sample

ODWALV30

ODWALV3X

ODWALV40

ODWALV50

LRWCOZ10

LRWCOZ IX

LRWCOZ20

LRWCOZ 30

ODWRZY10

ODWRZY1X

ODWRZW10

ODWRZW20

LRWRZZ10

LRWRZZ20

LRWRZZ2X

LRWRLZ10

LRWRLZ20

LRWSGZ10

LRWSGZ20

ORWSPT10

ODWSPK10

ODWSPK20

ODWSPK30

ODIPLC20

LRIHAZ10

ODICAE10

ODIEMC30

ODIEMC3X

ODISMC10

ODISMC1X

ODMMIL10

ODMMIL20

ODMMIL30

ODMMIL40

Cl

790

670

750

580

8

5

6

7

580

560

480

160

15

16

18

40

14

36

160

86

620

460

450

470

17

340

490

460

490

460

540

200

410

150

F

12

25

11

11

5

4

4

4

20

10

14

12

10

7

6

13

5

5

9

7

13

10

11

20

3

11

13

11

10

11

14

10

11

18

N03

<50

340

<50

64

60

50

150

56

180

<50

<50

100

160

<50

56

<50

70

<50

310

<50

140

<50

120

220

<50

<50

84

<50

<50

<50

<50

53

69

<50

P04

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

<150

so4

3,500

2,900

3,300

2,000

53

36

34

48

870

820

1,000

220

380

87

110

160

59

73

405

730

2,800

990

1,200

740

32

790

800

760

770

210

2,200

720

1,900

1,440
60 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

WATER LEACHATE CATIONS

[Values in ppm]

Sample Al Ba Ca Co Cu Fe K La Li Mg Mn Na Ni Si Sr Zn

ODWRRR10

ODWRRR1X

ODWRRR20

ODWRRR2X

ODWRRR30

ORWRRR40

LRWRAZ10

LRWRAZ20

ODWRIS10

ODWALV10

ODWALV20

ODWALV30

ODWALV3X

ODWALV40

ODWALV50

LRWCOZ10

LRWCOZ1X

LRWCOZ20

LRWCOZ30

ODWRZY10

ODWRZY1X

ODWRZW10

LRWRZZ10

LRWRZZ20

LRWRZZ2X

ORWSPT10

ODWSPK10

ODWSPK20

ODWSPK30

ODIPLC20

LRIHAZ10

ODICAE10

ODIEMC30

ODIEMC3X

ODISMC10

ODISMC1X

ODMMIL20

ODMMIL30

ODMMIL40

<10 4.3

<10 4.1

<10 6.6

<10 3.4

<10 4.8

<10 5.1

<10 4.4

<10 5.1

<10 3.2

<10 3.8

<10 4.7

<10 6.7

<10 4.8

<10 3.3

<10 5.2

<10 5.9

<10 3.5

60 4.8

17 4.4

<10 3.2

<10 5.4

<10 4.7

<10 3.9

<10 5.3

<10 4.0

<10 4.2

<10 3.6

<10 4.4

<10 3.4

<10 5.8

<10 5.4

<10 6.7

<10 3.2

<10 2.2

<10 5.3

<10 2.9

<10 3.9

<10 4.8

<10 4.9

700

740

890

920

900

40

80

22

430

970

980

1,200

1,100

1,200

720

26

30

10

15

380

360

410

100

35

70

280

1,100

410

460

320

120

410

330

330

300

300

260

700

540

0.3

.3

.4

.3

.3

.3

.3

.3

.3

.3

.4

.3

.4

.3

.3

.3

.2

2.5

.3

.2

.3

.2

.2

.3

.2

.2

.3

.3

.2

.3

.3

.4

.3

.3

.2

.3

.3

.2

.3

<0.1

<. 1

.1

<. 1

<.l

<. 1

<. 1

<. 1

.3

<. 1

<.l

<. 1

<.l

<. 1

<.l

<.l

<. 1

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

<.l

<.l

<.l

<. 1

<.l

<.l

.3

<. 1

<. 1

<. 1

<.l

<. 1

<.l

.2

.3

<10 73

<10 73

<10 88

<10 87

<10 98

<10 <10

<10 <10

<10 <10

<10 54

<10 96

<10 95

<10 113

<10 107

<10 111

<10 76

<10 <10

<10 <10

<10 <10

<10 <10

<10 54

<10 51

<10 40

<10 <10

<10 <10

<10 <10

<10 35

<10 89

<10 48

<10 53

<10 38

10 30

<10 38

<10 36

<10 37

<10 38

<10 38

<10 30

<10 59

<10 49

<0.1

<. 1

<.l

<.l

<.l

<. 1

<. 1

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

<. 1

14.0

<.l

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

.1

.2

<.l

<. 1

<. 1

<. 1

<.l

<. 1

<. 1

<. 1

<.l

0.5

.3

.6

.6

<.5

<. 1

<. 1

<. 1

.1

.6

.6

.6

.3

.8

.2

.2

<.l

3.8

<.l

.2

.1

.2

<.l

<. 1

<.l

.1

.4

.1

.1

<. 1

<.l

.3

<. 1

<.l

.3

<.l

.1

.3

.1

70

80

90

90

100

<10

<10

<10

50

100

100

120

110

110

80

<10

<10

<10

<10

60

50

40

<10

<10

10

30

90

50

50

40

30

40

40

40

40

40

30

60

50

10

11

14

14

18

1

1

0

8

15

15

19

18

19

13

0

0

0

0

7

6

6

1

0

1

3

16

8

9

7

4

3

6

6

6

6

3

9

8

420

420

520

520

340

50

50

50

200

400

410

510

460

480

380

30

30

40

20

350

340

280

80

80

80

140

400

290

290

300

90

230

270

260

260

250

200

310

230

0.2 <]

.9 <!

1.0 <]

.8 <]

.7 <]

.6 <]

.8 <]

.6 <]

3.9 <]

.8 <]

.6 <]

.9 <]

.6 <]

1.0 <]

.6 <]

.6 <]

.7 <]

.8 <]

.9 <]

.7 <]

.5 <]

.9 <]

.6 <1

.8 <]

.6 <1

.9 <1

.7 <]

.8 <]

.6 <]

.8 <]

.7 <]

.6 <]

.4 <]

.8 <]

.8 <1

.7 <]

.9 <]

.6 <]

.6 <]

LO 30

10 20

LO 30

LO 20

LO 20

LO <10

LO <10

LO 20

[0 20

LO 30

LO 30

LO 30

LO 30

LO 30

LO 30

LO <10

[0 20

LO 20

[0 110

LO 10

LO 20

LO 20

LO 20

LO 20

LO 20

LO 30

[0 30

LO 20

LO 20

LO 20

LO 20

LO 30

LO <10

LO 10

LO <10

LO <10

LO 10

LO 20

LO 20

2.7

2.7

3.3

3.3

3.4

.2

.4

.2

1.8

3.5

3.5

4.3

3.8

4.2

2.8

.2

.2

<. 1

.1

1.6

1.5

1.7

.4

.2

3.3

1.0

3.8

1.8

1.9

1.5

.8

1.6

1.5

1.6

1.4

1.4

1.3

2.6

2.0

0.3 <0.1

.2 <.l

<.l <.l

.1 <.l

.2 <.l

.2 <. 1

<. 1 <. 1

.2 <. 1

.2 <.l

.1 <.l

.2 <.l

.2 <. 1

.2 <.l

.2 <.l

.2 <.l

.1 <.l

.1 <.l

<.l 5.7

.3 <.l

.2 <.l

.2 <.l

.1 <.l

.2 <.l

.2 <. 1

<.l <.l

.2 <.l

.2 <.l

.2 <.l

.2 <.l

.1 <. 1

.2 <.l

.2 <.l

.2 <.l

.1 <. 1

.2 <.l

<. 1 <.l

.2 <.l

.1 <. 1

.2 <.l

<0.1

<. 1

<.l

<.l

<.l

<.l

<. 1

<. 1

.3

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

<. 1

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

<.l

<. 1

<. 1

<.l

<.l

<.l

<. 1

<. 1

<.l
LEACHATE CHEMISTRY OF ASH 

H2SO4 LEACHATE ANIONS

[Values in ppm]

61

Sample

LRWSHP10

LRWSHP20

LRWSHP30

LRWSHP40

LRWSHP50

LRWSHP60

LRWSHP70

LRWSHP80

LRWSHP90

LRWSHPOO

ODWRRR10

ODWRRR1X

ODWRRR20

ODWRRR2X

ODWRRR30

ORWRRR40

ORWRRR50

LRWYVZ10

LRWYVZ20

LRWRAZ10

LRWRAZ20

LRWELZ10

LRWYKZ40

Cl

130

1,100

550

380

350

260

230

34

29

29

580

330

860

840

540

24

62

24

28

40

28

80

130

F

55

62

54

37

40

52

50

14

34

17

69

67

66

67

82

23

10

32

36

41

38

60

59

N03

<50

<50

<50

<50

<50

<50

<50

<50

67

<50

110

95

56

<50

60

50

66

70

71

<50

<50

73

110

P04

1,150

1,130

1,000

700

750

1,080

1,150

430

800

520

1,100

1,020

930

900

1,200

520

250

800

880

1,180

880

1,030

930

Sample

LRWYKZ50

LRWCRZ10

LRWCRZ20

ODWRIS10

LRWMLZ10

LRWMLZ1X

LRWMLZ20

LRWMLZ2X

LRWMLZ30

LRWMLZ40

ODWALV10

ODWALV20

ODWALV30

ODWALV3X

ODWALV40

ODWALV50

LRWCOZ10

LRWCOZ1X

LRWCOZ20

LRWCOZ30

ODWRZY10

ODWRZY1X

ODWRZW10

Cl

79

35

36

370

73

61

74

73

56

31

710

840

930

860

900

700

20

32

34

23

750

680

290

F

45

44

43

60

48

14

47

43

46

45

83

34

93

84

90

75

36

48

41

53

48

48

52

N03

200

150

78

210

110

120

64

69

78

<50

<50

170

110

97

<50

76

<50

77

70

70

65

<50

78

P04

780

900

880

980

1,000

900

980

900

950

900

1,300

1,250

1,350

1,350

1,330

1,180

950

1,230

1,050

1,350

900

830

900

Sample

ODWRZW20

LRWRZZ10

LRWRZZ20

LRWRZZ2X

LRWRLZ10

LRWRLZ20

LRWSGZ10

LRWSGZ20

ORWSPT10

ODWSPK10

ODWSPK20

ODWSPK30

ODIPLC20

LRIHAZ10

ODICAE10

ODIEMC30

ODIEMC3X

ODISMC10

ODISMCIX

ODMMIL10

ODMMIL20

ODMMIL30

ODMMIL40

Cl

200

41

42

46

80

53

80

230

140

770

510

460

540

6

440

610

570

280

570

320

130

490

200

F

40

46

41

42

42

42

46

47

63

88

55

61

43

36

56

46

49

46

46

81

48

71

29

N03

71

<50

53

<50

59

<50

<50

<50

<50

<50

<50

<50

69

<50

60

53

<59

<50

59

70

63

91

<50

P04

730

850

830

880

1,000

930

1,000

1,000

1,030

1,250

1,000

1,050

880

750

1,000

950

850

800

980

1,250

900

1,130

1,130
62 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

H2SO4 LEACHATE CATIONS

[Values in ppm]

Sample

ODWRRR10

ODWRRR1X

ODWRRR20

ODWRRR2X

ODWRRR30

ORWRRR40

LRWRAZ10

LRWRAZ20

ODWRIS10

ODWALV10

ODWALV20

ODWALV30

ODWALV3X

ODWALV40

ODWALV50

LRWCOZ10

LRWCOZ1X

LRWCOZ20

LRWCOZ30

ODWRZY10

ODWRZY1X

ODWRZW10

LRWRZZ10

LRWRZZ20

LRWRZZ2X

ORWSPT10

ODWSPK10

ODWSPK20

ODWSPK30

ODIPLC20

LRIHAZ10

ODICAE10

ODIEMC30

ODIEMC3X

ODISMC10

ODISMC1X

ODMMIL20

ODMMIL30

ODMMIL40

Al

530

545

540

516

582

196

207

358

365

543

549

602

565

604

530

210

240

328

401

395

401

387

399

411

397

464

541

412

397

368

354

422

360

337

358

354

346

503

453

Ba

1.8

2.0

2.2

2.1

2.5

1.7

1.8

2.0

1.5

2.1

2.5

1.9

2.3

2.2

2.0

2.0

2.2

1.9

2.3

2.1

1.9

2.1

2.2

1.8

2.1

2.1

1.8

2.5

1.5

3.2

2.6

2.1

2.0

1.8

2.1

1.5

2.0

2.2

2.0

Ca

2,100

2,200

2,300

2,200

2,500

740

1,100

1,000

1,500

2,600

2,600

3,000

2,700

2,900

2,100

990

1,100

960

2,100

1,300

1,300

1,400

1,100

1,000

1,000

1,500

2,600

1,500

1,500

1,200

910

1,800

1,200

1,200

1,200

1,200

1,200

2,000

1,700

Co

0.5

.5

.5

.6

.7

<.l

.3

.2

.3

.7

.7

.4

.7

.6

.4

.3

.3

.2

.4

.3

.4

.2

.2

<. 1

.2

.5

.3

.3

.3

.2

.4

.2

.2

.2

.2

.2

.2

.3

.3

Cu

5.0

5.3

6.7

6.9

7.1

2.9

3.1

6.5

8.7

5.3

4.9

5.6

4.9

5.9

6.7

3.3

3.5

5.6

.4

6.7

6.6

7.2

6.7

7.0

6.4

6.2

7.0

9.3

8.5

9.2

5.3

7.0

9.2

8.7

8.1

7.5

5.5

8.4

5.2

Fe

820

820

620

580

740

270

340

380

360

790

810

780

750

790

630

260

300

310

23

380

380

350

400

400

410

550

670

400

380

280

350

440

260

250

280

270

290

380

420

K

540

520

500

430

530

170

200

230

290

530

530

530

500

540

440

170

220

190

470

280

290

220

250

250

230

360

470

290

280

210

210

280

200

190

200

190

190

310

300

La

2.7

3.2

3.0

2.8

3.2

1.4

1.8

1.8

2.7

3.3

4.0

4.1

3.9

3.8

3.0

1.8

2.2

1.8

1.8

1.7

2.0

1.7

1.8

1.7

1.5

2.5

3.4

2.2

2.2

1.7

1.7

2.2

1.8

1.6

1.6

1.6

1.9

3.2

2.9

Li

1.0

.7

1.0

.8

.9

.2

<.l

.1

.3

1.0

.9

.9

1.2

1.2

.6

<.l

<.l

.3

.1

.7

.6

<. 1

.3

.1

.3

.2

.6

.3

.4

.2

.2

.2

.2

.4

.1

.2

.2

.6

.5

Mg

500

500

460

420

490

150

200

230

260

500

510

500

480

510

410

170

210

190

460

270

280

220

240

240

230

340

440

270

260

200

200

270

200

180

190

190

190

300

280

Mn

63

66

63

60

72

16

23

24

30

74

75

81

77

80

57

20

22

20

36

32

33

28

21

21

22

39

67

37

37

25

17

40

23

23

25

25

21

39

31

Na

510

530

610

600

460

100

78

150

270

470

480

600

530

590

490

58

73

120

20

480

500

410

220

210

200

230

500

420

410

410

160

380

390

390

380

390

330

440

320

Ni

0.7

.8

1.0

1.1

.9

<.l

.4

.1

8.2

1.1

1.4

1.2

.8

.8

.3

.6

.3

.5

.9

.3

.4

.3

<.l

.2

.6

.5

.7

<.l

.4

.3

<.l

<. 1

.2

.8

<.l

<.l

<.l

.8

.4

P

390

400

310

300

430

230

400

320

400

460

470

490

480

480

430

390

420

370

450

310

320

340

310

310

320

360

450

390

380

330

330

360

330

330

330

340

350

420

420

Si

280

290

280

250

290

120

120

170

190

290

300

300

300

310

260

130

160

160

630

180

180

170

190

200

180

20

280

200

180

170

160

240

160

150

160

150

160

230

230

Sr

6.6

6.9

7.1

6.8

7.9

1.8

2.5

2.8

4.3

7.5

7.6

8.7

8.2

8.6

6.4

2.1

2.4

2.5

13.0

4.5

4.3

4.2

3.3

3.0

3.0

4.2

7.5

4.7

4.6

4.0

3.0

5.7

4.1

3.9

3.9

3.8

3.8

6.1

4.8

V

1.7

1.7

1.5

1.4

1.6

.6

.9

1.0

1.4

1.6

1.7

1.7

1.6

1.8

1.4

.8

.9

.9

.3

.9

1.0

.9

.9

.9

1.0

1.3

1.5

1.1

1.1

.9

.8

1.0

.8

.9

.8

.8

.8

1.5

1.4

Y

2.9

3.1

2.8

2.7

3.3

1.2

1.8

1.7

2.6

3.5

3.6

3.6

3.6

3.7

2.9

1.9

2.1

1.8

2.6

1.8

1.9

1.8

1.7

1.6

1.8

2.5

3.5

2.3

2.3

1.8

1.7

2.2

1.8

1.7

1.8

1.8

1.8

3.0

2.7

Zn

4.3

4.4

7.0

7.1

6.0

1.7

1.9

2.8

9.9

4.9

4.9

5.2

5.0

5.1

4.2

1.6

2.2

1.9

1.3

2.7

2.5

2.4

1.9

2.2

2.3

3.7

5.2

2.9

2.9

2.1

2.6

12.0

2.5

2.2

2.3

2.3

2.3

3.4

3.7
LEACHATE CHEMISTRY OF ASH 63

HNO3 LEACHATE ANIONS

[Values in ppm]

Sample

ODWALV30

ODWALV3X

ODWRZY10

LRWRZZ2X

LRIHAZ10

F

77

80

45

39

32

Cl

880

770

660

38

30

P0 4

1,200

1,200

400

560

470

so 4

4,100

3,600

1,200

400

500

OTHER MEASUREMENTS

Specific Catlon 

Sample conductivity

(micromhos/cm) p

ODWRRR10

ODWRRR1X

ODWRRR20

ODWRRR2X

ODWRRR30

ORWRRR40

LRWRAZ10

LRWRAZ20

ODWRIS10

ODWALV10

ODWALV20

ODWALV30

ODWALV3X

ODWALV40

ODWALV50

LRWCOZ10

LRWCOZ1X

LRWCOZ20

LRWCOZ30

ODWRZY10

0.47

.50

.63

.66

.55

<.20

<.20

<.20

.33

.67

.63

.80

.72

.69

.38

<.20

<.20

<.20

<.20

.35

6.2

6.4

7.1

7.5

7.5

.5

1.4

1.2

3.1

7.8

7.8

10.3

8.7

8.1

5.6

.8

.9

.8

6.9

2.9

exchange capacity 

(meq/lOOg)

K

0.2

.2

.1

.6

.2

<.l

<.l

<. 1

<.l

.1

.1

.2

.2

.2

.2

<. 1

<.l

<. 1

.9

<. 1

Mg

0.8

.8

1.0

1.0

1.1

<. 1

<.l

<. 1

.5

1.0

1.1

1.2

1.2

1.2

.8

<.l

.1

<.l

3.8

.6

Na

1.8

1.8

2.2

2.5

1.4

<. 1

.2

.2

.8

1.7

1.7

2.2

2.0

2.0

1.6

<. 1

<.l

<. 1

<.l

1.4

Specific 

Sample conductivity

Cation

(micromhos/cm) Ca

ODWRZY1X

ODWRZW10

LRWRZZ10

LRWRZZ20

LRWRZZ2X

ORWSPT10

ODWSPK10

ODWSPK20

ODWSPK30

ODIPLC20

LRIHAZ10

ODICAE10

ODIEMC30

ODIEMC3X

ODISMC10

ODISMC1X

ODMMIL20

ODMMIL30

ODMMIL40

0.32

.32

<.20

<.20

<.20

<.20

.65

.30

.35

.31

<.20

.32

.30

.20

.30

.28

.23

.39

.33

3.0

3.2

1.7

1.4

1.5

3.2

7.7

3.1

3.6

2.3

1.0

4.1

2.3

2.4

2.3

1.9

2.1

5.0

3.5

exchange capacity 

(meq/lOOg)

K Mg

<0.1 0.6

<.l .4

<.l .2

<.l .2

<.l .2

<.l .5

<.l .9

<.l .5

<.l .6

<. 1 .4

<.l .3

<. 1 .5

<.l .4

<. 1 .4

<.l .4

<. 1 .3

<.l .3

<. 1 .6

.2 .4

Na

1.5

1.2

.4

.4

.4

.5

1.7

1.2

1.2

1.1

.2

1.0

1.1

1.1

1.0

.9

.9

1.4

.9
64 CHEMISTRY OF ASH AND LEACHATES, MOUNT ST. HELENS, WASHINGTON

APPENDIX D. ESTIMATE OF ANALYTICAL ERROR IN CHEMICAL CONCENTRATION DATA FOR

LEACHATES

Analytical precision is estimated by the geometric error for each chemical species determined. The geometric error is the antilog of the 

log standard error, and is calculated from the logarithms of the differences in measured concentrations between samples that are members 

of pairs of analytical replicates (splits). The use of logarithmic data minimizes the perturbing effect of uncommon, extreme-value data upon 

the final value of the error parameter. The number of sample pairs from whose data the error parameter calculation was made are also listed 

in the appendix.

For anions (Cl~, F", PO^3, and SO'2), geometric error was calculated from concentration values of four pairs of samples. For samples with 

qualified values (below detection limit, where only an upper limit is given), a value of 0.7 times the detection limit was substituted and used 

in the calculation. The number of pairs free of qualified values is given in the table.

LEACHATE CHEMICAL ANALYSES AND CATION EXCHANGE CAPACITY

[Geometric error for specific conductivity, 1.10, determined on six pairs]

Chemical Geometric 

species error

Number of 

pairs

De ionized water leach

Cl

F

N03

so4

Ba

Ca

Co

K

Li

Mg

Mn

Na

Ni

Si

Sr

V

HN03 leach

Cl

F

P04

so4

1.16

1.30

2.00

1.37

1.34

1.17

1.22

1.02

1.60

1.10

1.22

1.03

1.49

1.38

1.87

1.47

1.85

1.12

1.21

1.52

10

10

2

10

8

8

8

6

4

6

8

8

8

5

8

5

1

1

1

1

Chemical 

species

Geometric 

error

Number of 

pairs

H2 S04 leach

Cl

F

N03

P04

Al

Ba

Ca

Co

Cu

Fe

K

La

Li

Mg

Mn

Na

Ni

P

Si

Sr

V

Y

Zn

1.27

1.33

1.36

1.09

1.04

1.11

1.04

1.32

1.05

1.'04

1.07

1.08

1.42

1.06

1.03

1.06

1.54

1.02

1.06

1.04

1.06

1.04

1.08

10

10

4

10

8

8

8

7

8

8

8

8

7

8

8

8

7

8

8

8

8

8

8

Chemical Geometric Number of 

species error pairs

Cation exchange capacity

Ca 1.07 8

K 1.49 3

Mg 1.11 7

Na 1.05 7

if- U.S. GOVERNMENT PRINTING OFF ICE: 1987-773-047/66000