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U.S. GEOLOGICAL SURVEY

Open-File Report 

By Tricia A. Lincoln, Debra A. Horan-Ross, 

Michael R. McHale, and Gregory B. Lawrence

Troy, New York

2001

01-71

Quality-Assurance Data for Routine Water 

Analyses by the U.S. Geological Survey 

Laboratory in Troy, New York—

July 1993 through June 1995
U.S. DEPARTMENT OF THE INTERIOR

Gale A. Norton, Secretary

U.S. GEOLOGICAL SURVEY

Gordon P. Eaton, Director

The use of firm, trade, and brand names in this report is for identification purposes only and does

not constitute endorsement by the U.S. Geological Survey

For addtional information write to: Copies of this report can be purchased

U.S. Geological Survey

Information Services

Box 25286, Mail Stop 417

Denver Federal Center

Denver, CO 80225-0046

from:

District Chief

U.S. Geological Survey

425 Jordan Road

Troy, New York 12180
Contents III

CONTENTS

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

Introduction .......................................................................................................................................................................... 2

Purpose and Scope....................................................................................................................................................... 2

Participating Projects .................................................................................................................................................. 2

Quality-Assurance/Quality-Control Program Description ................................................................................................... 3

Quality-Control Samples ............................................................................................................................................ 3

Filter Blanks and Analytical Blanks ........................................................................................................................... 3

Triplicate Environmental Samples .............................................................................................................................. 4

U.S. Geological Survey's Standard Reference Sample Program ................................................................................ 4

Environment Canada’s LRTAP Interlaboratory Study ............................................................................................... 5

Blind Reference Samples ............................................................................................................................................ 5

Control-Chart Development and Evaluation ........................................................................................................................ 5

Quality-Control Samples ............................................................................................................................................ 5

Filter Blanks and Analytical Blanks ........................................................................................................................... 5

Triplicate Environmental Samples .............................................................................................................................. 5

Environment Canada’s LRTAP Interlaboratory Study ............................................................................................... 7

Blind Reference Samples ............................................................................................................................................ 7

Summary of Results............................................................................................................................................................... 7

A. Quality-Control Samples ....................................................................................................................................... 7

B. Filter Blanks and Analytical Blanks ...................................................................................................................... 8

C. Triplicate Environmental Samples ......................................................................................................................... 9

D. U.S. Geological Survey’s Standard Reference Sample Program............................................................................ 10

E. Environment Canada’s LRTAP Interlaboratory Study ........................................................................................... 11

F. Blind Reference Samples ........................................................................................................................................ 11

Selected References .............................................................................................................................................................. 12

FIGURES

1-5. Graphs showing results of quality-control data for water-sample analyses from July 1993 through June 1995.

1. High- and low-concentration quality-control samples

A. Acid-neutralizing capacity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

B. Aluminum, total monomeric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

C. Aluminum, total. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

D. Ammonium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

E. Calcium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

F. Carbon, dissolved inorganic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

G. Carbon, dissolved organic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

H. Carbon, dissolved organic (soil expulsions) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

I. Chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

J. Fluoride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

K. Magnesium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

L. Nitrate (ion chromatography) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

M. Nitrate (colorimetric method) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

N. pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

O. Potassium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

P. Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Q. Sodium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

R. Sulfate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
IV Contents

2. Filter blank and analytical blank samples

A. Aluminum, total monomeric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

B. Aluminum, organic monomeric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

C. Aluminum, total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

D. Ammonium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

E. Calcium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

F. Carbon, dissolved organic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

G. Chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

H. Magnesium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

I. Nitrate (ion chromatography). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

J. Potassium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

K. Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

L. Sodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

M. Sulfate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3. Triplicate environmental samples

A1.Acid-neutralizing capacity (for triplicate means not in the range of +20 μeq/L) . . . . . . . . . . . . . . . . . . . . . . . . . 21

A2.Acid-neutralizing capacity (for triplicate means in the range of +20 μeq/L) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

B. Aluminum, total monomeric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

C. Aluminum, organic monomeric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

D. Aluminum, total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

E. Calcium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

F. Carbon, dissolved organic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

G. Chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

H. Magnesium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

I. Nitrate (ion chromatography). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

J. pH. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

K. Potassium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

L. Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

M. Sodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

N. Sulfate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

4. Environment Canada’s LRTAP Interlaboratory Study

A1.Acid-neutralizing capacity (for samples not in the range of +20 μeq/L). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

A2.Acid-neutralizing capacity (for samples in the range of +20 μeq/L). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

B. Ammonium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

C. Calcium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

D. Carbon, dissolved organic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

E. Chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

F. Magnesium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

G. Nitrate (ion chromatography). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

H. pH. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

I. Potassium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

J. Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

K. Sodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

L. Sulfate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5. Blind Reference Samples

A. Calcium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

B. Chloride . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

C. Magnesium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

D. pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

E. Potassium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

F. Sodium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

G. Sulfate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Contents V

TABLES

1. Number of environmental samples and quality-control samples analyzed by USGS Laboratory, and summary 

of quality control (QC) data for each constituent from July 1993 through June 1995 . . . . . . . . . . . . . . . . . . . . . . . . 4

2. Reporting limits and data-quality objectives for accuracy, precision, and blanks for solution analyses performed 

by the U.S. Geological Survey Laboratory in Troy, N.Y., July 1993 through June 1995. . . . . . . . . . . . . . . . . . . . . . 6

3. Results obtained by Troy, N.Y. Laboratory for U.S. Geological Survey Standard Reference Sample (SRS) 

Program, July 1993 through June 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

ABBREVIATED UNITS OF MEASUREMENT

mg/L milligrams per liter

μeq/L microequivalents per liter

μmol/L micromoles per liter

Other Abbreviations

ANC acid-neutralizing capacity

CV coefficient of variation

DI deionized water

DQO data-quality objective

LRTAP Long-Range Transport of Atmospheric Pollutants

MCV mean concentration value

MPV most probable value

QA quality assurance

QC quality control

QC-high high-concentration quality-control sample

QC-low low-concentration quality-control sample

SRS Standard Reference Sample

USGS U.S. Geological Survey 
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Quality-Assurance Data for Routine Water Analyse

by the U.S. Geological Survey Laboratory in Troy, 

New York, July 1993 through June 1995

By Tricia A. Lincoln, Debra A. Horan-Ross, Michael R. McHale, and 

Gregory B. Lawrence

Abstract

A laboratory for analysis of low-ionicstrength water has been developed at the U.S. 

Geological Survey (USGS) office in Troy, N.Y., to 

analyze samples collected by USGS projects in 

the Northeast. The laboratory’s quality-assurance 

program is based on internal and interlaboratory 

quality-assurance samples and quality-control 

procedures developed to ensure proper sample 

collection, processing, and analysis. The qualityassurance/quality-control data are stored in the 

laboratory’s SAS1 data-management system, 

which provides efficient review, compilation, and 

plotting of quality-assurance/quality-control data. 

This report presents and discusses samples 

analyzed from July 1993 through June 1995.

Quality-control results for 18 analytical 

procedures were evaluated for bias and precision. 

Control charts show that data from seven of the 

analytical procedures were biased throughout the 

analysis period for either high-concentration or 

low-concentration samples but were within 

control limits; these procedures were: acidneutralizing capacity, dissolved inorganic carbon, 

dissolved organic carbon (soil expulsions), 

chloride, magnesium, nitrate (colorimetric 

method), and pH. Three of the analytical 

procedures were occasionally biased but were 

within control limits; they were: calcium (high 

high-concentration samples for May 1995), 

dissolved organic carbon (high for highconcentration samples from January through 

September 1994), and fluoride (high in sample

for April and June 1994). No quality-control 

sample has been developed for the organic 

monomeric aluminum procedure.

Results from the filter-blank and analytical

blank analyses indicate that all analytical 

procedures in which blanks were run were with

control limits, although values for a few blanks 

were outside the control limits. Blanks were no

analyzed for acid-neutralizing capacity, dissolv

inorganic carbon, fluoride, nitrate (colorimetric 

method), or pH.

Sampling and analysis precision are evalua

herein in terms of the coefficient of variation 

obtained for triplicate samples in 14 of the 18 

procedures. Data-quality objectives were met b

more than 90 percent of the samples analyzed 

all procedures except total monomeric aluminu

(85 percent of samples met objectives), total 

aluminum (70 percent of samples met objective

and dissolved organic carbon (85 percent of 

samples met objectives). Triplicate samples we

not analyzed for ammonium, fluoride, dissolve

inorganic carbon, or nitrate (colorimetric metho

Results of the USGS interlaboratory Stand

Reference Sample Program indicated high data 

quality with a median result of 3.6 of a possibl

1 Use of trade, product, or firm names in this publication is for 

descriptive purposes only and does not imply endorsement by the 

U.S. Government.
2 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, New 

July 1993 through June 1995

4.0. Environment Canada’s LRTAP 

interlaboratory study results indicated that more 

than 85 percent of the samples met data-quality 

objectives in 6 of the 12 analyses; exceptions 

were calcium, dissolved organic carbon, chloride, 

pH, potassium, and sodium. Data-quality 

objectives were not met for calcium samples in 

one LRTAP study, but 94 percent of samples 

analyzed were within control limits for the 

remaining studies. Data-quality objectives were 

not met by 35 percent of samples analyzed for 

dissolved organic carbon, but 94 percent of 

sample values were within 20 percent of the most 

probable value. Data-quality objectives were not 

met for 30 percent of samples analyzed for 

chloride, but 90 percent of sample values were 

within 20 percent of the most probable value. 

Measurements of samples with a pH above 6.0 

were biased high in 54 percent of the samples, 

although 85 percent of the samples met dataquality objectives for pH measurements below 

6.0. Data-quality objectives for potassium and 

sodium were not met in one study (only 33 

percent of the samples analyzed met the 

objectives), although 85 percent of the sample 

values were within control limits for the other 

studies. Measured sodium values were above the 

upper control limit in all studies.

Results from blind reference-sample analyses 

indicated that data-quality objectives were met by 

more than 80 percent of the chloride, pH, 

potassium, and sodium samples. Data-quality 

objectives were not met by 35 percent of the 

magnesium samples and 45 percent of the sulfate 

samples. Data-quality objectives were not met by 

calcium samples.

INTRODUCTION

The U.S. Geological Survey (USGS) maintains a 

laboratory at its Troy, N.Y., office to analyze lowionic-strength water for USGS watershed-research 

projects that require major-ion analyses of 

precipitation, soil-water, shallow ground-water, and 

stream-water samples. The methods used in this 

laboratory are described in detail in Lawrence and 

others (1995).

Analyses done during the 2-year period 

1993-June 1995) represented by this report w

neutralizing capacity (ANC), total monomer

aluminum, organic monomeric aluminum, to

aluminum, ammonium, calcium, dissolved i

carbon (DIC), dissolved organic carbon (DO

chloride, fluoride, magnesium, nitrate (ion 

chromatograph and colorimetric method), p

potassium, silicon, sodium, and sulfate.

Purpose and Scope

This report documents the quality-assur

practices and quality-control data of this lab

and is intended for use by current and prosp

cooperating agencies. It (1) describes quality

and quality-assurance procedures of the labo

presents graphs showing the results from an

quality-control samples, filter blanks and an

blanks, triplicate environmental samples, an

reference samples, and (3) explains analytic

and outliers and the corrective actions taken

Participating Projects

The numbers and types of samples analy

the laboratory during the 2-year period are 

summarized below, by the project for which 

associated; numbers in parentheses are USG

numbers.

Project: Neversink Watershed Study (NY91

Cooperator: New York City Department of 

Environmental Protection

Analyses: 997 samples (stream water, shallo

water, and snow).

Project: Biogeochemical Processes that Co

Nitrogen Cycling and Associated H

and Aluminum Leaching in an Und

Headwater Basin (NY91-204)

Cooperator: New York City Department of 

Environmental Protection

Analyses: 3,100 samples (stream water, sha

ground-water, soil water solution, 

by expulsion method, and snow).

Project: Long-Term Monitoring of Five Str

the Catskill Mountains (NY85-152

Cooperator: U.S. Environmental Protection 

Analyses: 370 stream-water samples.
Project: Forest-Floor Aluminum and Calcium 

Chemistry—Relations with Acid Deposition, 

Root Vitality, Stand Dynamics, and Red 

Spruce (NY92-208)

Cooperator: U.S. Forest Service

Analyses: 360 samples (stream water, soil water 

solution, and soil water by expulsion 

method).

Project: Variable Source-Area Control of Episodic 

Stream Chemistry (NY92-209)

Cooperator: U.S. Forest Service

Analyses: 348 stream-water samples.

Additional information on projects of the New 

York District is given in Lee (1996).

QUALITY-ASSURANCE/QUALITY-CONTROL 

(QA/QC) PROGRAM DESCRIPTION

The quality of the data produced at this laboratory 

is maintained by adherence to the standard operating 

procedures described in Lawrence and others (1995) 

and by participation in externally administered 

quality-assurance (QA) programs. Results of QA data 

are evaluated by the laboratory supervisor and primary 

analysts, and appropriate corrective action is taken 

when needed. The data quality objectives (DQO’s) are 

based on (1) the precision and accuracy levels 

generally required in projects using the Troy 

Laboratory, and (2) the analytical limits of the 

methods used.

Quality-Control Samples

Quality-control (QC) samples are used to 

determine the accuracy of an instrument’s calibration 

and to detect variations in instrument response within 

an analytical run. Source material for all QC samples 

either is obtained from a manufacturer other than the 

producer of the source material used to make 

calibration standards, or is obtained from a different lot.

The concentrations of QC samples are chosen to 

bracket the expected range of the environmentalsample concentrations. A high-concentration QC 

sample and a low-concentration QC sample (referred 

to herein as QC-high and QC-low) are prepared for 

most analyses; exceptions are inorganic monomeric 

aluminum, for which column efficiency is used to 

determine the acceptability of the data, and fluorid

for which only one QC sample is prepared because 

concentrations encountered by the laboratory are 

within a narrow range.

Quality-control samples are analyzed immediat

after calibration, after every 10 analyses of 

environmental samples, and at the end of each run. 

Exceptions to the frequency of QC-sample analyse

are ANC (after every 17 environmental samples), a

pH (after every 10 to 13 environmental samples). Q

samples that do not meet DQO’s for accuracy are 

rerun, and if the value is acceptable, the run is 

continued. If the rerun-QC-sample value is 

unacceptable, the environmental-sample data 

preceding it are rejected, and the instrument is 

recalibrated. Only accepted QC-sample and 

environmental-sample data are entered into the 

database. An exception to this practice occurs when 

the volume of an environmental sample is insuffici

for a rerun. In this case, the environmental-sample 

QC data are entered into the database and flagged, 

the project chief then decides whether to accept or 

reject these data. Analytical results of QC samples 

included in this report to indicate (1) the frequency 

out-of-control data that are not rerun, and (2) biase

and trends of within control data. The number of 

samples analyzed, and a summary of the qualityassurance data, are given in table 1.

Filter Blanks and Analytical Blanks

A filter blank and an analytical blank are includ

in each group of 50 environmental samples. 

Filter blanks are aliquots of deionized (DI) wa

that are processed and analyzed in the same manne

environmental samples. Filter blanks are analyzed 

only for constituents that require filtration. Filter-bl

analysis indicates whether contamination has occur

during bottle-washing procedures, filtration, sampl

preservation, or laboratory analysis.

Analytical blanks are aliquots of DI water that 

processed and analyzed as environmental samples, 

except that the filtration step is omitted. 

Contamination found in analytical blanks may be 

attributed to bottle washing, sample preservation, o

laboratory analysis, but not to filtration.

Quality-Assurance/Quality-Control (QA/QC) Program Description
4 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, New 

July 1993 through June 1995

Triplicate Environmental Samples

One set of field triplicate environmental samples is 

included in each group of 50 samples. A field triplicate 

set consists of three consecutive samples taken from 

one site. The purpose of environmental triplicate 

samples is to determine long-term analytical precision. 

Precision can be affected by bottle washing, samplecollection, sample processing procedures, and 

analysis. Environmental samples are selected for 

triplicate analysis on a rotating basis to ensure a wide 

range of sample concentrations.

Triplicate environmental samples were analyzed 

consecutively on the instrument sample tray until 

December 1993. Presently, the laboratory al

between consecutively analyzing a triplicate 

separating the triplicate set over the day’s an

U.S. Geological Survey’s Standard Re

Sample Program

The USGS Standard Reference Sample 

(SRS) conducts a national interlaboratory an

evaluation program semiannually. The Troy 

participates in the low-ionic-strength compo

this program. Reference samples are prefixe

and are analyzed for calcium, chloride, flu

Table 1. Number of environmental and quality-control samples analyzed by USGS Laboratory, and summary of qu

(QC) data for each constituent, July 1993 through June 1995. 

[QC-high = high concentration quality-control sample. QC-low = low concentration quality-control sample.]

Summary of QC data

Number of samples analyzed

Number of QC 

samples exceeding 

control limits

QC-high QC-low

Number of Q

exceeding c

by more tha

Constituent QC-high 

Project

samples

QC samples

QC-high QC-low

Acid-neutralizing capacity 3713 68 307 0 0 0 

Aluminum, total monomeric 4038 564 564 1 2 0 

Aluminum, organic monomeric 4038 0 0 0 0 0 

Aluminum, total 4594 730 736 11 7 4 

Ammonium 1381 394 394 7 7 0 

Calcium 5707 509 509 2 7 0 

Carbon, dissolved inorganic 289 68 68 1 1 0 

Carbon, dissolved organic 4204 560 561 0 14 0 

Carbon, dissolved organic (soil 

expulsions) 352 33 33 0 3 0 

Chloride 4186 589 589 0 0 0 

Fluoride 2041 405 0 1 0 1 

Magnesium 4304 514 514 5 2 2 

Nitrate (ion chromatography) 4450 602 603 0 1 0 

Nitrate (colorimetric method) 976 195 195 2 1 0 

pH 4124 115 507 1 2 0 

Potassium 3745 437 437 1 6 1 

Silicon 4175 615 615 6 3 0 

Sodium 3750 444 444 1 4 0 

Sulfate 4171 586 586 0 0 0 
magnesium, pH, potassium, sodium, and sulfate. 

Typically, the low-ionic-strength sample consists of 

snow that is collected, melted, filtered, and possibly 

spiked with reagent-grade chemicals to meet the goals 

of the SRS program. Laboratory personnel are aware 

of the presence of the SRS sample at the time of 

analysis but do not know the constituent concentrations 

until a published report is received from the USGS. 

The most probable value (MPV) for each constituent is 

calculated by nonparametric statistics. Individual 

laboratory performances are rated numerically; the 

highest score is 4.0, and the lowest is 0.0.

Environment Canada’s LRTAP 

Interlaboratory Study

The Troy laboratory participates in the LRTAP 

interlaboratory quality-assurance program, in which a 

set of 10 samples is analyzed three times per year. The 

samples are obtained from predominantly low-ionicstrength waters from various sources, such as 

precipitation, snow, lakes, and streams throughout 

North America and western Europe. The 

concentrations of the constituents in the LRTAP 

samples are similar to those of the environmental 

samples analyzed at the Troy laboratory. Laboratory 

results are compared with a median concentration 

value (MCV) calculated from results from all 

participants in the LRTAP program. Laboratory 

personnel are aware of the presence of LRTAP 

samples at the time of analysis but do not know the 

MCV of the constituents until Environment Canada 

publishes a report at the conclusion of each study. 

Blind Reference Samples

The Troy laboratory analyzes USGS SRS 

samples that have been processed as routine 

environmental samples. These blind reference 

samples are disguised and therefore assumed by the 

analyst to be a project sample. The blind reference 

samples have most probable values that are reported 

by the USGS SRS program. The SRS samples are 

rotated as supplies are exhausted, and periodically the 

identity of the blind reference sample is changed. One 

blind reference sample is included in each set of 50 

environmental samples.

CONTROL-CHART DEVELOPMENT 

AND EVALUATION

Control charts (figs. 1-5) are plots of QC data i

relation to time; in this report, they are used to (1) 

confirm that laboratory DQO’s are met for individu

QC samples, (2) detect long-term biases within the 

control limits, and (3) provide comparisons with 

results from other laboratories. 

A constituent analysis is considered biased if 7

percent or more of the points on a chart are above o

below the theoretical value.

Quality-Control Samples

Results of QC sample analyses are plotted on 

control charts in which the central line is equal to t

theoretical value of the control sample. Each analy

has prescribed control limits that have been 

established to meet project DQO’s (table 2). The lim

are represented by the upper and lower control-lim

lines on each chart. QC-high and QC-low samples 

plotted on separate graphs by constituent and date o

analysis, and the control charts are evaluated for tren

and(or) bias. All data are reported in micromoles p

liter (μmol/L) except pH (pH units) and ANC 

(microequivalents per liter, μeq/L).

During the period represented by this report, seve

quality-control samples concentrations were changed 

reflect typical environmental-sample concentrations (

example, fig. 1M). The concentration changes are 

discussed in the summary of results. 

Filter Blanks and Analytical Blanks

Results from blank analyses (fig. 2) are plotted 

control charts, by constituent. The control limits we

established to meet project DQO’s (table 2) and are 

represented by horizontal lines on the control chart

Data are plotted as concentration in relation to date 

collection. The control charts are evaluated to ident

possible contamination or positive interferences.

Triplicate Environmental Samples

The coefficient of variation (CV) for each 

triplicate sample concentration is plotted by 

constituent and date of collection in figure 3. Data 

Control-Chart Development and Evaluation
6 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, New 

July 1993 through June 1995

with mean concentrations less than the defined 

reporting limit (table 2) are excluded. The DQO for all 

constituents is a CV of less than 10 percent, with the 

exception of total monomeric aluminum and organic 

monomeric aluminum, which are 15 percent. Each 

circle within the control charts represents the CV of a 

triplicate environmental sample. 

where: s = standard deviation, and 

= arithmetic mean of triplicate s

ANC triplicate sample means were plott

graphs. The first graph shows the CV for trip

sample means outside the range of -20 to +2

(fig. 3A1); the second graph shows values th

CV s

x = --( ) 100

x

Table 2. Reporting limits and data-quality objectives for accuracy, precision, and blanks for solution analyses

performed by the U.S. Geological Survey Laboratory in Troy, N.Y., July 1993 through June 1995.

[DQO, data-quality objective. μmol/L, micromoles per liter. CV, coefficient of variation. ANC, acid-neutralizing capacity. pH and ANC valu

(in parentheses) are in pH units and microequivalents per liter, respectively.]

1

 ANC: Values in parentheses are in microequivalents per liter. For values within +20 microequivalents per liter, an absolute 

data-quality objective of +6 microequivalents per liter is used for precision. 

2

 Quality-control samples for organic monomeric aluminum are unavailable.

3

 Concentrations are expressed as micromoles carbon per liter.

4

 pH: Percent error and coefficient of variation determined from [H+].

Constituent or property

Reporting 

limit 

(μmol/L)

Accuracy Precision

Filter a

analyt

blan

DQO

(μmo

Low-concentration 

quality-control sample

High-concentration 

quality-control sample

 DQO (CV)

DQO 

(percent 

error)

Concentration

(μmol/L)

DQO 

(percent 

error)

Concentration

(μmol/L)

Acid-neutralizing capacity 1 none 10 (-39.9) 10 (125) 10 non

Aluminum, total monomeric 1.5 15 7.41 10 18.5 15 0.7

Aluminum, organic monomeric 2 1.5 none none none none 15 0.7

Aluminum, total 1.0 20 1.0 10 15.0 10 0.5

Ammonium 2.0 15 7.14 10 17.9 10 1.0

Calcium 2.0 10 25.0 10 99.8 10 1.0

Carbon, dissolved inorganic3 41.0 15 83.3 10 416 10 non

Carbon, dissolved organic3 41.0 15 83.3 10 416 10 18

Carbon, dissolved organic (soil 

expulsions)3 41.0 10 416 10 1665 10 non

Chloride 2.0 10 8.47 10 84.7 10 0.5

Fluoride 0.5 15 1.58 none none 10 non

Magnesium 1.0 10 8.23 10 32.9 10 0.5

Nitrate (ion chromatography) 2.0 10 4.84 10 48.4 10 0.

Nitrate (colorimetric method) 5.0 15 42.9 10 100 10 non

pH4 none 10 (4.41) 20 (6.88) 10 non

Potassium 1.0 10 5.12 10 25.6 10 0.5

Silicon 6.0 10 35.6 10 107 10 3

Sodium 1.0 10 8.70 10 43.5 10 1.0

Sulfate 2.0 10 8.33 10 83.3 10 0.
between -20 and +20 μeq/L (fig. 3A2). Each symbol 

on the graph represents the difference between the 

triplicate sample mean and the individual values of 

that triplicate sample.

Environment Canada’s LRTAP Interlaboratory 

Study

Interlaboratory comparison graphs (fig. 4) are 

based on results from LRTAP samples and represent 

LRTAP studies from July 1993 through March 1995. 

The Troy laboratory did not participate in Study 34 

(October 1993). Samples with MCV’s less than the 

reporting limits were excluded from the graphs. The 

MCV and the control limits of +10 percent are 

represented by lines on the graphs; the percent 

difference (D) is calculated as:

D = [(AV - MCV)/MCV] x 100

where: AV = analyzed value, and

MCV = mean concentration value

A separate graph is shown for ANC values in t

+20 to -20 μeq/L range; results for these samples a

plotted as the difference between the laboratory va

and the MCV (fig. 4A2). The LRTAP pH results 

consist of two sets of data—pH values less than 6.0

and pH values equal to or greater than 6.00. The tw

sets of data have different DQO’s, which are 

represented by a solid line and a dashed line on the 

graph (fig. 4H).

Blind Reference Samples

Results from blind reference sample analyses 

(fig.5) are plotted on separate control charts, by 

constituent and date of analysis. Samples with MP

less than the reporting limits were excluded from th

graphs. The MPV and the control limits of +10 perc

are represented by lines on the graphs; the percent 

difference (D) is calculated as:

D = [(AV-MPV)/MPV]x100

where: AV = analyzed value, and

MPV = most probable value

SUMMARY OF RESULTS

The following sections summarize the results for (A) quality-control samples (fig. 1, p. 14-18), (B) filter 

blanks and analytical blanks (fig 2, p.19-20), (C) triplicate environmental samples (fig. 3, p. 21-22), (D) SRS 

samples (table 3), (E) LRTAP samples (fig. 4, p. 23-24), and (F) blind samples (fig. 5, p. 25).

A. Quality-Control Samples

Acid-Neutralizing Capacity (fig. 1A).– DQO’s were 

met by 100 percent of the samples. No apparent 

trends or biases were evident among the QC-low 

sample. The QC-high sample had a low bias 

during this time period.

Aluminum, Total Monomeric (fig. 1B).–DQO’s were 

met by 99 percent of the samples. No apparent 

trends or biases were evident among the QC-high 

and QC-low samples.

Aluminum, Organic Monomeric.–No QC sample has 

been developed for this analysis.

Aluminum, Total (fig. 1C).–DQO’s were met by 99 

percent of the samples. No apparent trends or 

biases were evident among the QC-high and QClow samples.

Ammonium (fig. 1D).–DQO’s were met by 99 perc

of the samples. No apparent trends or biases w

evident among the QC-high and QC-low samp

Calcium (fig. 1E).–DQO’s were met by 99 percen

the samples. A slight high bias was observed f

analyses performed in May 1995.

Carbon, Dissolved Inorganic (fig. 1F).–DQO’s w

met by 99 percent of the samples. The QC-hig

and QC-low samples were biased high during t

time period.

Carbon, Dissolved Organic (fig. 1G).–DQO’s w

met by 99 percent of the samples. A high bias w

observed for the QC-high sample in 1994. No 

apparent trend or bias was evident for the QC

low sample.

Carbon, Dissolved Organic (soil expulsions) (f

1H).–DQO’s were met by 95 percent of the 

Summary of Results
8 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, New 

July 1993 through June 1995

samples. The QC-high graph shows a slight 

high bias.

Chloride (fig. 1I).–DQO’s were met by 100 percent of 

the samples. The QC-high graph illustrates a low 

bias until December 1993; this was due to an error 

in preparation of QC stock solution and has been 

corrected. The QC-low sample shows a possible 

high bias which has been corrected by adding a 

blank standard to the calibration curve. Data was 

flagged in the database.

Fluoride (fig. 1J).–DQO’s were met by 99 percent of the 

samples. The high bias in early 1994 is attributed to 

the QC stock solution, which was replaced.

Magnesium (fig. 1K).–DQO’s were met by 99 percent 

of the samples. The QC-high and QC-low samples 

appear to have a slight low bias.

Nitrate (ion chromatography) (fig. 1L).–DQO’s 

were met by 99 percent of the samples. No 

apparent trends or biases were evident among the 

QC-high and QC-low samples.

Nitrate (colorimetric method) (fig. 1M).–DQO’s 

were met by 99 percent of the samples. The QChigh and QC-low samples appear to be biased low; 

this is attributed to incomplete conversion of 

nitrate to nitrite by the cadmium-reduction 

column. The column was operating at 90-percent 

efficiency during this period. Project chiefs were 

notified of the low bias; data were not changed. In 

July 1994, the QC-high and QC-low 

concentrations were changed to 99.99 and 42.88 

μmol/L, respectively, to reflect typical 

environmental-sample concentrations.

pH (fig. 1N).–DQO’s were met by 99 percent of the 

samples. No apparent trends or biases were evident 

among the QC-high sample. The QC-low sample 

had a high bias during this time period.

Potassium (fig. 1O).–DQO’s were met by 99 percent of 

the samples. No apparent trends or biases were 

evident among the QC-high and QC-low samples. 

The potassium QC-low concentration was increased 

from 5.12 to 6.40 μmol/L in 1995 to reflect typical 

environmental-sample concentrations.

Silicon (fig. 1P).–DQO’s were met by 99 percent of the 

samples. No apparent trends or biases were 

evident among QC-low samples. The QC-high 

sample had a slight high bias during this time 

period. The QC-low control limit was lowered to 

10 percent in response to the improvement and 

refinement of the analysis.

Sodium (fig. 1Q).–DQO’s were met by 99 

the samples. No apparent trends or bia

evident among the QC-high and QC-lo

samples. The sodium QC-low concentr

increased from a theoretical value of 8

10.88 μmol/L in 1995 to reflect typica

environmental-sample concentrations.

Sulfate (fig. 1R).–DQO’s were met by 100 

of the samples. No apparent trends or 

were evident among the QC-high sam

QC-low sample had a slight high bias d

time period.

B. Filter Blanks and Analytical Blanks

Acid-Neutralizing Capacity.–Blanks were 

analyzed for this constituent.

Aluminum, Total Monomeric (fig. 2A).–T

was met by 93 percent of the samples. H

results were obtained in July and Augus

The instrument software, which calculat

analysis results, was upgraded, and an i

default setting was discovered that subt

absorbance of the leading baseline from 

sample peak absorbance. This has been 

the software now calculates an average a

from the leading and trailing baselines a

subtracts this value from the sample pea

data were flagged in the database.

Aluminum, Organic Monomeric (fig. 2B)

DQO was met by 94 percent of the sam

blank results were obtained in July and 

1993. The instrument software, which c

sample-analysis results, was upgraded, 

incorrect default setting was discovered 

subtracted the absorbance of the leading 

from the sample peak absorbance. This 

corrected; the software now calculates a

absorbance from the leading and trailing 

and subtracts this value from the sample 

Sample data was flagged in the databas

Aluminum, Total (fig. 2C).–The DQO was 

percent of the samples. No systematic tr

evident for this analysis.

Ammonium (fig. 2D).–The DQO was met b

percent of the samples. No systematic tr

evident for this analysis. Routine blank

discontinued for the ammonium analysi

October of 1993. Ammonium was not an
every environmental sample after this date. 

Samples were frozen and then analyzed in batches 

throughout the year.

Calcium (fig. 2E).–The DQO was met by 91 percent of 

the samples. No systematic trends were evident for 

this analysis.

Carbon Dissolved Inorganic.–Blanks were not 

analyzed for this constituent.

Carbon, Dissolved Organic (fig. 2F).–The DQO was 

met by 84 percent of the samples. A new 

instrument has been purchased, which is expected 

to increase the percent of samples that met the 

DQO.

Carbon, Dissolved Organic (soil expulsions).–

Blanks were not analyzed for this constituent.

Chloride (fig. 2G).–The DQO was met by 80 percent 

of the samples.

Fluoride.–Blanks were not analyzed for this 

constituent.

Magnesium (fig. 2H).–The DQO was met by 96 

percent of the samples. No systematic trends were 

evident for this analysis.

Nitrate (ion chromatography) (fig. 2I).–The DQO 

was met by 93 percent of the samples. No 

systematic trends were evident for this analysis.

Nitrate (colorimetric method).–Blanks were not 

analyzed for this constituent.

pH.—Blanks were not analyzed for this constituent.

Potassium (fig. 2J).–The DQO was met by 88 percent 

of the samples. No systematic trends were evident 

for this analysis.

Silicon (fig. 2K).–The DQO was met by 78 percent of 

the samples. No systematic trends were evident for 

this analysis.

Sodium (fig. 2L).–The DQO was met by 90 percent of 

the samples. No systematic trends were evident for 

this analysis.

Sulfate (fig. 2M).–The DQO was met by 97 percent of 

the samples. No systematic trends were evident for 

this analysis.

C. Triplicate Environmental Samples

Acid-Neutralizing Capacity (figs. 3A1 and 3A2).–

The DQO was met by 96 percent of the triplicate 

samples.

Aluminum, Total Monomeric (fig. 3B).–The DQ

was met by 78 percent of the triplicate sample

Aluminum, Organic Monomeric (fig. 3C).–The 

DQO was met by 93 percent of the triplicate 

samples.

Aluminum, Total (fig. 3D).–The established precis

DQO was exceeded by 42 percent of the samp

Use of a graphite furnace for aluminum analys

has been discontinued. An ICP has been 

purchased, and improved results are expected.

Ammonium.–Triplicate samples were not analyze

for ammonium.

Calcium (fig. 3E).–The DQO was met by 91 percen

the triplicate samples.

Carbon Dissolved Inorganic.–Triplicate samples 

were not analyzed for ammonium.

Carbon, Dissolved Organic (fig. 3F).–The DQO w

met by 82 percent of the triplicate samples.

Carbon, Dissolved Organic (soil expulsions).–

Triplicate samples were not analyzed for 

ammonium.

Chloride (fig. 3G).–The DQO was met by 89 perc

of the triplicate samples.

Fluoride.–Triplicate samples were not analyzed 

ammonium.

Magnesium (fig. 3H).–The DQO was met by 98 

percent of the triplicate samples.

Nitrate (ion chromatography) (fig. 3I).–The DQO 

was met by 89 percent of the triplicate sample

Nitrate (colorimetric method).–Triplicate sampl

were not analyzed for ammonium.

pH (fig. 3J).–The DQO was met by 100 percent of 

triplicate samples.

Potassium (fig. 3K).–The DQO was met by 89 perc

of the triplicate samples.

Silicon (fig. 3L).–The DQO was met by 97 percen

the triplicate samples.

Sodium (fig. 3M).–The DQO was met by 92 percen

the triplicate samples.

Sulfate (fig. 3N).–The DQO was met by 100 percen

the triplicate samples.

Summary of Results
10 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, N

July 1993 through June 1995

D. U.S. Geological Survey’s Standard 

Reference Sample (SRS) Program

Laboratory results for all SRS samples were rated 

between “good” and “excellent.” Overall laboratory 

performance ratings for each SRS sample were:

P-21 4.0

P-22 3.7

P-23 3.4

P-24 3.3

All analyses received a rating of 3 or 4 f

constituent with two exceptions. pH received 

for P-22 but improved to 4 in both samples t

followed. Sodium received a 2 for P-23.

Table 3. Results obtained by Troy, N.Y., Laboratory for U.S. Geological Survey 

Standard Reference Sample (SRS) Program, October 1993 through May 1995

(MPV, most probable value; TV, Troy laboratory value; mg/L, milligrams per liter; 

dash indicates no results reported)

Analyte

MPV, TV, 

and ratinga

SRS sample number

P-21

10/93b

P-22

4/94c

P-23 

10/94d

P-24 

5/95e

Calcium MPV, mg/L — 0.725 1.13 —

TV, mg/L — 0.760 1.20 —

Rating — 3 3 —

Chloride MPV, mg/L 3.90 2.92 0.310 1.20

TV, mg/L 3.83 2.90 0.205 1.10

Rating 4 4 3 3

Fluoride MPV, mg/L — 0.028 0.120 —

TV, mg/L — 0.020 0.120 —

Rating — 4 4 —

Magnesium MPV, mg/L — 0.098 0.317 —

TV, mg/L — 0.100 0.320 —

Rating — 4 4 —

pH MPV 4.06 5.81 6.40 4.73

TV 4.06 5.60 6.33 4.72

Rating 4 2 4 4

Potassium MPV, mg/L — 0.203 0.483 —

TV, mg/L — 0.210 0.450 —

Rating — 4 3 —

Sodium MPV, mg/L — 1.70 0.500 —

TV, mg/L — 1.70 0.420 —

Rating — 4 2 —

Sulfate MPV, mg/L 0.50 0.728 1.28 0.338

TV, mg/L 0.46 0.785 1.27 0.335

Rating 4 4 4 4

a Laboratory rating system: 4 is highest score; 0 is lowest

b Sample described in Long and Farrar (1994a) c Sample described in Long and Farrar (1994b)

d Sample described in Long and Farrar (1995a) e Sample described in Long and Farrar (1995b)
E. Environment Canada’s LRTAP 

Interlaboratory Study

Environment Canada’s LRTAP program does not 

audit the analysis of total monomeric aluminum, 

organic monomeric aluminum, dissolved inorganic 

carbon, dissolved organic carbon (soil expulsions), 

fluoride, and nitrate (colorimetric method).

The laboratory did not submit results for total 

aluminum analyses during this time period.

Acid-Neutralizing Capacity (figs. 4A1 and 

4A2).—The DQO was met by 98 percent of the 

LRTAP samples. No trend or bias was evident.

Ammonium (fig. 4B).—The DQO was met by 

100 percent of the LRTAP samples. LRTAP samples 

were not run for ammonium after study 33. 

Environmental samples are no longer routinely 

analyzed for ammonium. Samples are selectively 

analyzed a few times yearly.

Calcium (fig. 4C).—The DQO was met by 76 

percent of the LRTAP samples. The low bias in study 

38 was due to incorrect dilutions of stock solutions.

Carbon, Dissolved Organic (fig. 4D).—The 

DQO was met by 70 percent of the LRTAP samples. 

The outliers were most often biased low.

Chloride (fig. 4E).—The DQO was met by 76 

percent of the LRTAP samples. All outliers were 

biased high.

Magnesium (fig. 4F).—The DQO was met by 

88 percent of the LRTAP samples. No trend or bias 

was evident.

Nitrate (ion chromatography).—The DQO was 

met by 97 percent of the LRTAP samples.

pH (fig. 4H).—The DQO was met by 85 percent 

of the LRTAP samples with a pH less than 6.00. 

Samples with a pH above 6.00 were biased high. The 

high number of pH measurements that were biased 

high are most likely the result of a difference in 

methods used by the Troy laboratory and the other 

laboratories participating in the LRTAP program. The 

USGS method uses a millivolt-stability criterion to 

determine whether equilibration with the electrode has 

occurred. Most laboratories use a preset time for all 

samples. Low-pH samples equilibrate more quickly 

than high-pH samples. Laboratories that use the same 

equilibration time for low and high pH samples will, 

therefore, bias their measurement of a high-pH sample 

if this sample is preceded by a low-pH sample. This 

relation explains why about half of the LRTAP pH 

measurements appear to be biased high. Successful 

measurement of the pH of quality-control samples 

with values above 6.7 supports this conclusion.

Potassium (fig. 4I).—The DQO was met by 66 

percent of the LRTAP samples. All outliers were 

biased low.

Silicon (fig. 4J).—The DQO for silicon was n

met. All data was biased high. An ICP was recentl

installed for silicon analysis, and improved results 

are expected.

Sodium (fig. 4K).—The DQO was met by 66 

percent of the LRTAP samples. The low percentage 

was primarily the result of a low bias in all sample

from study 35. The cause is uncertain, but 80 perce

of the samples since that study have met the DQO’

Sulfate (fig. 4L).—The DQO was met by 98 

percent of the samples. No trend or bias was eviden

F. Blind Reference Samples

Blind reference samples are analyzed for all 

constituents for which the SRS program reports. Th

blind reference samples are not analyzed for acidneutralizing capacity, total monomeric aluminum, 

organic monomeric aluminum, total aluminum, 

ammonium, dissolved inorganic carbon, dissolved 

organic carbon, dissolved organic carbon (soil 

expulsions), fluoride, nitrate (ion chromatography)

nitrate (colorimetric method), and silicon.

Calcium (fig. 5A).–The DQO for calcium was not m

The calcium method used during this period 

included a lanthanum chloride reagent, whose 

concentration was too low to mask interferenc

Environmental-sample data were erroneously l

The method was corrected, and project sample

were reanalyzed for calcium. Initial data were 

flagged as erroneous, and reanalysis data were 

added to the database.

Chloride (fig. 5B).–The DQO was met by 91 perc

of the blind reference samples. No trend or bia

was evident.

Magnesium (fig. 5C).–The DQO was met by 59 

percent of the blind reference samples.

pH (fig. 5D).–The DQO was met by 100 percent 

the blind reference samples. No trend or bias 

was evident.

Potassium (fig. 5E).–The DQO was met by 77 perc

of the blind reference samples. No trend or bia

was evident.

Summary of Results
12 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, N

July 1993 through June 1995

Sodium (fig. 5F).–The DQO was met by 80 percent of 

the blind reference samples. Most of the outliers 

were biased low.

Sulfate (fig. 5G).–The DQO was met by 51 percent of 

the samples. All outliers were biased low. The SRS 

sample that was used as the blind reference sample 

during this period was 8 years old. The sulfate 

MPV’s may have been inaccurate after this long 

time period. More recent SRS samples are 

currently used for blind reference samples, and 

results have improved.

SELECTED REFERENCES

Lawrence, G.B., Lincoln, T.A., Horan-Ross, D.A., Olson, 

M.L., and Waldron, L.A., 1995, Analytical methods of 

the U.S. Geological Survey’s New York District Water 

Analysis Laboratory: U.S. Geological Survey OpenFile Report 95-416, 78 p.

Lee, M.P., 1996, U.S. Geological Survey Water-Resources 

Programs in the New York District–fiscal years 1993-

94: U.S. Geological Survey Open-File Report 96-113, 

48 p.

Long, H. K., and Farrar, J. W., 1994a, Report on the U.S. 

Geological Survey’s evaluation program for Standard 

Reference Samples distributed in October 1

(trace constituents), M-128 (major constitu

(nutrients), N-41 (nutrients), P-21 (low ioni

and Hg-17 (mercury), AMW-3 (acid mine w

WW-1 (whole water): U.S Geological Surv

File Report 94-42, 177 p.

_____1994b, Report on the U.S. Geological Sur

evaluation program for Standard Reference 

distributed in April 1994: T-129 (trace cons

M-130 (major constituents), N-42 (nutrient

(low ionic strength), and Hg-18 (mercury): 

Geological Survey Open-File Report 94-36

_____1995a, Report on the U.S. Geological Sur

evaluation program for Standard Reference 

distributed in October 1994: T-131 (trace co

T-133 (trace constituents), M-132 (major co

N-43 (nutrients), N-44 (nutrients), P-23 (low 

strength), and Hg-19 (mercury): U.S. Geolo

Survey Open-File Report 95-117, 139 p. 

_____1995b, Report on the U.S. Geological Sur

evaluation program for Standard Reference 

distributed in May 1995: T-135 (trace const

134 (major constituents), N-45 (nutrients), 

(nutrients), P-24 (low ionic strength), Hg-2

(mercury), and SED-5 (bed material): U.S. 

Survey Open-File Report 95-395, 135 p.
Figures 1-5

Figures
14 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, N

July 1993 through June 1995

1993 1994 1995

Figure 1. High- and low-concentration quality control samples: A. Acid-neutralizing capacity. B. Aluminum, total

monomeric. C. Aluminum, total. D. Ammonium.

B. ALUMINUM, TOTAL

MONOMERIC

C. ALUMINUM, TOTAL

100

110

120

130

140

150

160

ACID-NEUTRALIZING CAPACITY,

IN MICROEQUIVALENTS PER LITER

10

11

12

13

14

15

16

17

18

19

20

ALUMINUM, TOTAL

IN MICROMOLES PER LITER 0.5

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1.4

1.5

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

ALUMINUM, TOTAL

IN MICROMOLES PER LITER

High Concentration Sample High Concentration Sample

Low Concentration Sample

DATE OF ANALYSIS

-50

-45

-40

-35

-30

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

ACID NEUTRALIZING CAPACITY,

IN MICROEQUIVALENTS PER LITER

Low Concentration Sample

6

7

8

9

10

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

ALUMINUM, TOTAL MONOMERIC,

IN MICROMOLES PER LITER

CONTROL SAMPLE THEORETICAL VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

DATE OF ANALYSIS

15

17

19

21

23

25

ALUMINUM, TOTAL MONOMERIC,

IN MICROMOLES PER LITER

High Concentration Sample

14

16

18

20

22

AMMONIUM,

IN MICROMOLES PER LITER

D. AMMONIUM

4

6

8

10

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

AMMONIUM,

IN MICROMOLES PER LITER

DATE OF ANALYSIS

Low Concentration Sample

High Concentration Sample

A. ACID-NEUTRALIZING CAPACITY

DATE OF ANALYSIS

Low Concentration Sample

1993 1994 1995

1993 1994 1995 1993 1994 1995
Figure 1. High- and low-concentration quality control samples (continued): E. Calcium. F. Carbon, dissolved

inorganic. G. Carbon, dissolved organic. H. Carbon, dissolved organic (soil expulsions).

50

60

70

80

90

100

110

120

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Ma

CARBON, DISSOLVED ORGANIC,

IN MICROMOLES PER LITER

CONTROL SAMPLE THEORETICAL VALUE UPPER CONTROL LIMIT LOWER CONTRO

80

85

90

95

100

105

110

115

120

125

CALCIUM,

IN MICROMOLES PER LITER 20

22

24

26

28

30

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

CALCIUM,

IN MICROMOLES PER LITER

High Concentration Sample

Low Concentration Sample

E. CALCIUM

DATE OF ANALYSIS

F. CARBON, DISSOLVED INORGANIC

360

380

400

420

440

460

480

500

CARBON, DISSOLVED INORGANIC,

IN MICROMOLES PER LITER 60

70

80

90

100

110

120

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

CARBON, DISSOLVED INORGANIC,

IN MICROMOLES PER LITER

High Concentration Sample

Low Concentration Sample

DATE OF ANALYSIS

G. CARBON, DISSOLVED ORG

300

320

340

360

380

400

420

440

460

480

500

CARBON, DISSOLVED ORGANIC,

IN MICROMOLES PER LITER

High Concentration Sample

Low Concentration Sample

DATE OF ANALYSIS

1250

1350

1450

1550

1650

1750

1850

1950

2050

CARBON, DISSOLVED ORGANIC,

IN MICROMOLES PER LITER 300

350

400

450

500

550

600

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Ma

CARBON, DISSOLVED ORGANIC,

IN MICROMOLES PER LITER

High Concentration Sample

Low Concentration Sample

H. CARBON, DISSOLVED ORGANIC (SOIL EXP

DATE OF ANALYSIS

1993 1994 1995 1993 1994 

1993 1994 1995 1993 1994 1

Figure 1
16 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, N

July 1993 through June 1995

Figure 1. High- and low-concentration quality control samples (continued): I. Chloride. J. Fluoride.

K. Magnesium. L. Nitrate (ion chromatography).

6.5

7

7.5

8

8.5

9

9.5

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

MAGNESIUM,

IN MICROMOLES PER LITER

CONTROL SAMPLE THEORETICAL VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

I. CHLORIDE

65

75

85

95

105

CHLORIDE,

IN MICROMOLES PER LITER

7

8

9

10

11

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

CHLORIDE,

IN MICROMOLES PER LITER

High Concentration Sample

Low Concentration Sample

DATE OF ANALYSIS

J. FLUORIDE

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

FLUORIDE,

IN MICROMOLES PER LITER

Control Sample

DATE OF ANALYSIS

K. MAGNESIUM

26

28

30

32

34

36

38

40

42

MAGNESIUM,

IN MICROMOLES PER LITER

DATE OF ANALYSIS

High Concentration Sample

Low Concentration Sample

DATE OF ANALYSIS

35

40

45

50

55

60

NITRATE,

IN MICROMOLES PER LITER

High Concentration Sample

3.5

4

4.5

5

5.5

6

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

NITRATE,

IN MICROMOLES PER LITER

Low Concentration Sample

L. NITRATE (ION CHROMATOGRAPH

1993 1994 1995 1993 1994 1995

1993 1994 1995

1993 1994 1995
Figure 1. High- and low-concentration quality control samples (continued): M. Nitrate (colorimetric method). N. pH

O. Potassium. P. Silicon.

4

4.5

5

5.5

6

6.5

7

7.5

8

Jul Sep Nov Jan Mar May Jul Sep Nov Jan M

POTASIUM,

IN MICROMOLES PER LITER

M. NITRATE (COLORIMETRIC METHOD)

50

60

70

80

90

100

110

120

NITRATE,

IN MICROMOLES PER LITER

High Concentration Sample

15

25

35

45

55

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

NITRATE,

IN MICROMOLES PER LITER

DATE OF ANALYSIS

Low Concentration Sample

6.6

6.7

6.8

6.9

7

7.1

7.2

PH 4.3

4.35

4.4

4.45

4.5

4.55

4.6

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

PH

CONTROL SAMPLE THEORETICAL VALUE CONTROL LIMIT LOWER CONTRO

N. pH

DATE OF ANALYSIS

High Concentration Sample

Low Concentration Sample

80

90

100

110

120

130

140

SILICON,

IN MICROMOLES PER LITER 25

27

29

31

33

35

37

39

41

43

45

Jul Sep Nov Jan Mar May Jul Sep Nov Jan M

SILICON,

IN MICROMOLES PER LITER

P. SILICON

DATE OF ANALYSIS

High Concentration Sample

Low Concentration Sample

20

21

22

23

24

25

26

27

28

29

30

POTASIUM,

IN MICROMOLES PER LITER

O. POTASSIUM

DATE OF ANALYSIS

High Concentration Sample

Low Concentration Sample

1993 1994 1995 1993 1994 1

1993 1994 1995 1993 1994 

Figure 1
18 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, N

July 1993 through June 1995

Figure 1. High- and low-concentration quality control samples (continued): Q. Sodium. R. Sulfate.

7

8

9

10

11

12

13

14

15

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

SODIUM,

IN MICROMOLES PER LITER

Q. SODIUM

35

37

39

41

43

45

47

49

51

53

55

SODIUM,

IN MICROMOLES PER LITER

DATE OF ANALYSIS

High Concentration Sample

Low Concentration Sample

6

6.5

7

7.5

8

8.5

9

9.5

10

10.5

11

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

SULFATE,

IN MICROMOLES PER LITER

CONTROL SAMPLE THEORETICAL VALUE UPPER CONTROL LIMIT LOWER CONTROL LIMIT

60

65

70

75

80

85

90

95

100

105

110

SULFATE,

IN MICROMOLES PER LITER

R. SULFATE

DATE OF ANALYSIS

High Concentration Sample

Low Concentration Sample

1993 1994 1995

1993 1994 1995
-1

-0.5

0

0.5

1

1.5

2

A. ALUMINUM, TOTAL MONOMERIC

-1

-0.5

0

0.5

1

1.5

2

-0.5

0

0.5

1

1.5

2

2.5

3

-0.5

0

0.5

1

1.5

2

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

D. AMMONIUM

C. ALUMINUM, TOTAL

B. ALUMINUM, ORGANIC MONOMERIC

-2

-1

0

1

2

3

4

E. CALCIUM

-100

-50

0

50

100

150

200

F. CARBON, DISSOLVED ORGAN

-10

0

10

20

30

40

50

60

G. CHLORIDE

-0.5

0

0.5

1

1.5

2

2.5

3

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar 

ANALYTICAL BLANK FILTER BLANK CONTROL LIMIT

1993 1994 1995 1993 1994 1

DATE OF COLLECTION DATE OF COLLECTION

H. MAGNESIUM

Figure 2. Filter-blank and analytical-blank samples: A. Aluminum, total monomeric. B. Aluminum, organic

monomeric. C. Aluminum, total. D. Ammonium. E. Calcium. F. Carbon, dissolved organic. G. Chloride. H.

Magnesium.

Figure 2
20 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, N

July 1993 through June 1995

-5

0

5

10

15

20

25

30

35

I. NITRATE (ION CHROMATOGRAPHY)

-1

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

-2

-1

0

1

2

3

4

5

6

7

8

J. POTASSIUM

K. SILICON

-5

0

5

10

15

20

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

ANALYTICAL BLANK FILTER BLANK CONTROL LIMIT

1993 1994 1995

1993 1994 

DATE OF COLLECTION

DATE OF COLLECTIO

-10

0

10

20

30

40

50

Jul Sep Nov Jan Mar May Jul Sep Nov 

L. SODIUM

M. SULFATE

Figure 2. Filter-blank and analytical-blank samples (continued): I. Nitrate (ion chromatography). J. Potas

Silicon. L. Sodium. M. Sulfate. NITRATE, IN MICROMOLES PER LITER POTASSIUM, IN MICROMOLES PER LITER SILICON, IN MICROMOLES PER LITER SODIUM, IN MICROMOLES PER LITER

SULFATE, 

IN MICROMOLES PER LITER
-40

-30

-20

-10

0

10

20

30

A1. ACID-NEUTRALIZING CAPACITY

(for triplicate means not in ± 20 μeq l-1 range)

0

5

10

15

20

25

30

35

B. ALUMINUM, TOTAL MONOMERIC

-25

-5

15

35

55

75

95

Jul Oct Jan Apr Jul Oct Jan Apr

COEFFICIENT OF VARIATION PERCENT LINE

C. ALUMINUM, ORGANIC MONOMERIC

Figure 3. Triplicate environmental samples: A1. Acid-neutralizing capacity (for triplicate means not in the range 

± 20 μeq l-1). A2. Acid-neutralizing capacity (for triplicate means in the range of ± 20 μeq l-1). B. Aluminum, total

monomeric. C. Aluminum, organic monomeric. D. Aluminum, total. E. Calcium. F. Carbon, dissolved organic.

 G. Chloride.

0

10

20

30

40

50

60

70

80

90

100

0

5

10

15

20

25

30

35

40

D. ALUMINUM, TOTAL

E. CALCIUM

0

10

20

30

40

50

60

F. CARBON, DISSOLVED ORGANIC

0

5

10

15

20

25

30

35

40

Jul Oct Jan Apr Jul Oct Jan Apr

G. CHLORIDE

DATE OF COLLECTION DATE OF COLLECTION

1993 1994 1995 1993 1994 199

A2.

-20

-15

-10

-5

0

5

10

15

20

DIFFERENCE FROM MEAN

CONTROL LIMITS

A2. ACID-NEUTRALIZING CAPACITY

(for triplicate means in ±20 μeq l-1range)

Figure
22 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, N

July 1993 through June 1995

0

5

10

15

20

25

30

H. MAGNESIUM

0

5

10

15

20

25

30

J. pH

0

5

10

15

20

25

30

Jul Oct Jan Apr Jul Oct Jan Apr

COEFFICIENT OF VARIATION 10 PERCENT LINE

K. POTASSIUM

0

2

4

6

8

10

12

14

16

18

L. SILICON

0

5

10

15

20

25

30

0

2

4

6

8

10

12

Jul Oct Jan Apr Jul Oct Ja

M. SODIUM

N. SULFATE

Figure 3. Triplicate environmental samples (continued): H. Magnesium. I. Nitrate (Ion Chromatography). J. 

Potassium. L. Silicon. M. Sodium. N. Sulfate.

DATE OF COLLECTION

DATE OF COLLECTION

1993 1994 1995

1993 1994 

0

10

20

30

40

50

60

70

80

90

I. NITRATE (ION

CHROMATOGRAPHY)

COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION

COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION COEFFICIENT OF VARIATION
-20

-15

-10

-5

0

5

10

15

20

-25

-20

-15

-10

-5

0

5

10

15

20

25

DIFFERENCE

STUDY 33 STUDY 35 STUDY 36 STUDY 37 STUDY 38

A1. ACID-NEUTRALIZING CAPACITY

(f or samples not in the range of ±20 μeq l-1)

A2. ACID NEUTRALIZING CAPACITY

(f or samples in the range of ±20 μeq l-1)

STUDY 33 STUDY 35 STUDY 36 STUDY 37 STUDY 38

-20

-15

-10

-5

0

5

10

15

20

STUDY 33 STUDY 35 STUDY 36 STUDY 37 STUDY 38

B. AMMONIUM

-60

-40

-20

0

20

40

60

PERCENT DIFFERENCE THEORETICAL VALUE UPPER CONTROL LIMIT LOWER CONTR

C. CALCIUM

STUDY 33 STUDY 35 STUDY 36 STUDY 37 STUDY 38

Figure 4. Environment Canada, LRTAP laboratory study: A1. Acid-neutralizing capacity (for means not in the ra

±20μeq l-1). A2. Acid-neutralizing capacity (for sample means in the range of ±20μeq l-1). B. Ammonium. C. Cal

D. Carbon, dissolved organic. E. Chloride. F. Magnesium. G. Nitrate (ion chromatography).

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

STUDY 33 STUDY 35 STUDY 36 STUDY 37 ST

D. CARBON, DISSOLVED ORGAN

-20

-10

0

10

20

30

40

50

60

E. CHLORIDE

STUDY 33 STUDY 35 STUDY 36 STUDY 37 ST

-100

-80

-60

-40

-20

0

20

40

F. MAGNESIUM

-20

-15

-10

-5

0

5

10

15

20

25

30

STUDY 33 STUDY 35 STUDY 36 STUDY 37 ST

STUDY 33 STUDY 35 STUDY 36 STUDY 37 ST

G. NITRATE (ION CHROMATOGRAP

LRTAP STUDIES 33 THROUGH 38 LRTAP STUDIES 33 THROUGH 38

Figure 4
24 Quality-Assurance Data for Routine Water Quality Analyses by the U.S. Geological Survey Laboratory in Troy, N

July 1993 through June 1995

-40

-20

0

20

40

60

80

100

120

140

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

PERCENT DIFFERENCE. pH<6.00

(Control 10%)

PERCENT DIFFERENCE. pH>6.00

(Control 20%)

STUDY 33 STUDY 35 STUDY 36 STUDY 37 STUDY 38

H. pH

-40

-30

-20

-10

0

10

20

30

40

DIFFERENCE FROM MEAN

 CONCENTRATION VALUE (IN PERCENT)

STUDY 33 STUDY 35 STUDY 36 STUDY 37 STUDY 38

I. POTASSIUM

-40

-30

-20

-10

0

10

20

30

40

DIFFERENCE FROM MEAN

 CONCENTRATION VALUE (IN PERCENT)

STUDY 33 STUDY 35 STUDY 36 STUDY 37 STUDY 38

J. SILICON

-60

-50

-40

-30

-20

-10

0

10

20

30

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

PERCENT DIFFERENCE THEORETICAL VALUE UPPER CONTROL LIMIT LOWER CO

K. SODIUM

STUDY 33 STUDY 35 STUDY 36 STUDY 37 STUDY 38

-20

-10

0

10

20

30

40

DIFFERENCE FROM MEAN

CONCENTRATION VALUE (IN PERCENT)

STUDY 33 STUDY 35 STUDY 36 STUDY 37 STU

L. SULFATE

LRTAP STUDIES 33 THROUGH 

LRTAP STUDIES 33 THROUGH 38

Figure 4. Environment Canada, LRTAP laboratory study (continued): H. pH. I. Potassium. J. Silicon. K. Sod

Sulfate.
-60

-40

-20

0

20

40

60

B. CHLORIDE

-20

-15

-10

-5

0

5

10

15

20

THEORETICAL VALUE UPPER CONTROL LIMIT LOWER CONTROL 

-25

-20

-15

-10

-5

0

5

10

15

20

25

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

-40

-30

-20

-10

0

10

20

30

40

E. POTASSIUM

D. pH

-40

-30

-20

-10

0

10

20

30

40

F. SODIUM

G. SULFATE

1993 1994 1995

1993 1994 1995

DATE OF COLLECTION

DATE OF COLLECTION

 . 

-50

-40

-30

-20

-10

0

10

20

30

40

50

PERCENT DIFFERENCE

A. CALCIUM

-40

-30

-20

-10

0

10

20

30

40

C. MAGNESIUM

Jul Sep Nov Jan Mar May Jul Sep Nov Jan Mar May

Figure 5. Analytical blind samples: A. Calcium. B. Chloride. C. Magnesium. D. pH. E. Potassium. F. Sodium. G. Su

Figure 5