°43oi D

Author Birge, Wesley J.

Corporate Author

RODOrt/ArtiOlB TitlO Aquatic Toxicology of Trace Elements of Coal and Fly

Ash

JOUmal/BOOk TltlU Energy and Environmental Stress in Aquatic Systems: s

Year

 1978

Month/Day

Color

 D

Number of Images 22

DflSCriptOn NOtOS

 Alvin L

-

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label, "Arsenic/Cacodylic Acid and Herbicide Blue". Doc. No.

CONF-771114

Thursday, February 14, 2002 Page 4301 of 4919
-from "^JvA/icaJl J>-<or/A«'6<« C*r., UUS

Series - V*. / 977

AQUATIC TOXICOLOGY OF TRACE ELEMENTS

OF COAL AND FLY ASH

WESJ_Ey.T SIR G K

T. H. Morgan School of Biological Sciences, University of Kentucky,

Lexington, Kentucky

ABSTRACT

Aquatic bioassays were performed on 22 coal elements, with developmental and

juvenile stages of fish and amphibians used as test organisms. For more sensitive

test species, LC50 values of 0.1 ppm or less were observed for 15 trace elements,

and LC] values ranged down to 0.1 to 0.2 ppb for mercury and silver. Studies

also were performed on the aqueous leaching characteristics and toxicological

properties of coal-produced fly ash. A 52-kg sample of precipitator-collected fly

ash was subjected to continuous flow-through washing for 2000 consecutive

hours in a bench-scale ash-settling pond. Chemical characteristics of the

simulated effluent compared closely with those recorded for actual ash-settling

ponds. During the first 500 hr of operation, conductivity averaged 690

iUmhos/cm, and a mean of 0.56 g/liter was observed for total dissolved solids.

Gradual decreases were observed thereafter. Effluent pH averaged 4.3 during the

first 500 hr but approached the level of influent water (7.1 to 7.9) by 2000 hr.

Maximum effluent concentrations detected for seven selected metals were 126

ppm Al, 766 ppb Zn, 518 ppb Cu, 500 ppb Cd, 370 ppb Ni, 87 ppb Hg, and 8

ppb Ag. Mean concentrations for the first 500 hr of elution were 32.6 ppm Al,

350 ppb Zn, 156 ppb Cd, 1 55 ppb Ni, 1 1 0 ppb Cu. '2.1 ppb Ag, and 1.8 ppb Hg.

All metals except mercury reached maximum levels within 500 hr, and

concentrations declined thereafter. Mean mercury levels increased to 27 and 15

ppb for the second and third 500-hr elution intervals Afte r 522 and 1033 hr of

elution time, continuous-flow treatment with undiluted ash effluent produced

100% mortality of frog and .sunt'ish eggs. A 0.1 dilutio n at 1033 hr resulted in

42'" hatehabiiit y of sunfish eggs. Afte r 1775 hr of continuous leaching,

undiluted ash effluen t and 0.1 and 0.01 dilution s gave survival frequencies of 57,

76, and (S89f for goldfish eggs, compared with 92~ for controls. Metals analyzed

for undiluted effluen t administered to goldfish were well below LCj determinations, except aluminum, which was present at the LC; ;, level.
220 BIRGE

With the increasing dependence on coal as a national energy source,

there is a serious need to investigate further the effects of coal

production and use on environmental health. Numerous recent

studies emphasize the extent to which coal utilization has grown

beyond our ability to identify fully the hazardous trace elements in

coal, quantify their release rates into the environment, and define

their biological and health-related effects (Ayer, 1974; Yavorsky and

Akhtar, 1974; Babu, 1975; Vaughan et al., 1975). Approximately

two-thikds of the over 60 elements that occur in coal have been

detected as environmental pollutants (Vitez, 1976). Although toxicological data are largely incomplete, most of the elements found in

coal and other fossil fuels are known to have at least some toxic

effects on animal species (National Academy of Sciences—National

Academy of Engineering, Committee, 1973; Smith, Ferguson, and

Carlson, 1975; Vitez, 1976).

The annual combustion of 600 million tons of coal constitutes

the major source of environmental contamination with coal trace

elements (Abel and Rancitelli, 1975; Bolton et al., 1975; Sheibley,

1975). The main sources of water pollution are power plants, which

dispose of more than 50 million tons/year of bottom ash and

precipitated fly ash (Rubin and McMichael, 1974; Chu, Nicholas, and

Ruane, 1975). Large quantities of water are used in sluicing ash

residues to settling ponds, and pond effluents contain toxic metals

that affect the quality of receiving waters (Theis, 1975; Hildebrand,

Cushman, and Carter, 1976). For each 1000-MW capacity, sluicingwater requirements for Tennessee Valley Authority (TVA) power

Stations average 11.5 million gal/day or 4.2 billion gal/year (Environmental Protection Agency, 1974; Chu, Nicholas, and Ruane, 1975).

Current projections indicate that the rate of coal combustion will

1

 double by the mid 1980s (Vaughan et al., 1975). Therefore, a better

; understanding of the aquatic toxicology of coal-derived contami-

\ nants is essential if we are to maximize coal use and also institute

J safeguards necessary to maintain reasonable and proper environ-

: mental health.

* In this study, aquatic bioassays were performed to establish a

comparative toxicological ranking for 22 coal elements, identify

those which may be particularly hazardous to aquatic ecosystems,

and provide quantitative data for use in further evaluations of

environmental standards and pollution-abatement technology. In

addition, a bench-scale settling pond was developed to simulate

fly-ash effluents and to investigate the aqueous leaching of toxic

elements. Continuous flow embryo—larval bioassays were used for in

situ monitoring of ash effluents to provide direct toxicological

evaluations on complex suites of trace cloments.
AQUATIC TOXICOLOGY OF TRACE ELEMENTS 221

MATERIALS AND METHODS

Aquatic Bioassays

Semistatic embryo—larval bioassays were performed on the

goldfish (Carassius auratus), the rainbow trout (Salmo gairdneri), and

the narrow-mouthed toad (Gastrophryne carolinensis) with rapidscan procedures previously described (Birge and Just, 1975). Eggs

were exposed to coal elements from fertilization through 4 days

posthatching, giving treatment periods of 7 days for toads and

goldfish and 28 days for trout. Test water and toxicant were

renewed at regular 12-hr intervals. Mean water hardness, with

standard error, was 195 ± 5.4 ppm CaCO3 for goldfish and toad

stages and 104 ± 2.0 for trout. Test water pH averaged 7.4 ± 0.1.

Dissolved oxygen was maintained near saturation by continuous,

moderate aeration. Other chemical and physical characteristics of the

reconstituted test water were described by Birge and Black (1977).

Water temperature was 13.0 ± 0.5°C for trout eggs and 22.0 ± 1.0°C

for other species.

Test organisms were examined daily to tabulate frequencies of

mortality and teratogenesis. Control adjusted LC1 and LCSO values

were calculated for combined test responses by log probit analysis

(Daum, 1969). Anomalous survivors were counted as lethals. Control

eggs were cultured simultaneously with experimentals and under

identical conditions, except for omission of toxic coal elements.

Minimum sample size was set at 150 eggs per culture.

The 22 coal elements and test compounds selected for bioassay

analysis are given in Table 1. Depending on the degree of anticipated

toxicity, exposure concentrations were initiated at 10 to 100 ppm

and continued at two- to tenfold dilutions until survival of

experimental animals equaled or approached that observed for

controls. Each coal element was administered at 10 to 14 exposure

levels. Elemental concentrations of test water were monitored by

atomic absorption spectrophotornetry with a model 503 Perkin—

Elmer unit equipped with an HGA-2100 graphite furnace and a

mercury analyzer (Perkin—Elmer Corp., 1973).

Aqueous Leaching of Fly Ash

A bench-scale Plexiglas settling pond was designed to investigate

the aqueous leaching characteristics of precipitator-collected fly ash

obtained from a local 1000-MW coal-fired power plant. A 52-kg

sample of dry ash was deposited in an 88.2-liter settling chamber. A

Gilson Minipuls II peristaltic pump (Gilson Medical Electronics, Inc.)

provided a cnnuni'ou ^ flow of water o\vr the ash bee1 at a rate of 1
222 BIRGE

TABLE 1

COAL TRACE ELEMENTS SELECTED

FOR BIO ASSAY EVALUATIONS

Trace

element

Aluminum

Antimony

Arsenic

Cadmium

Cobalt

Chromium

Copper

Germanium

Lanthanum

Lead

Manganese

Mercury

Molybdenum

Nickel

Silver

Selenium

Strontium

Thallium

Tin

Tungsten

Vanadium

Zinc

Bioassay

test compound

A1C13

SbCl3

NaAsO2

CdCl2

Co(NCM2

Cr03

CuSC-4

Ge02

LaCl3

PbCl2

MnCl2

HgCl2

Na2MoO4

NiCl2

AgN03

Na2SeO4

SrCl2

T1C13

SnCl2

Na2WO4

V205

ZnCl2

Concentration*

in coal, ppm

10,440—12,900

0.50—1.26

4.45-14.02

0.47—2.52

2.90—9.57

13.75—18.00

8.30-15.16

1.00—6.59

3.80—10.00

4.90—34.78

33.80-49.40

0.12—0.20

5.00-7.54

16.00—21.07

0.03-0.12

2.08-2.20

10.00—23.00

0.29—2.00

0.03-4.79

0.10—3.00

28.50-32.71

46—272

*The majority of values are from Ruch,

Gluskoter, and Shimp (1974), Fulkerson et al.

(1975), and Carter (1975) and represent means for

multiple coal samples taken largely from western

•Kentucky and southern Illinois. Lower means for

Ag, Tl, Sn, and W are from Lloyd (1976), and the

upper mean for Ag is from Vaughan et al. (1975).

liter/hr, giving a detention time of 42 hr. Water was discharged from

the settling chamber into an overflow-equipped effluent reservoir.

The ash-to-water ratio and the detention time were calculated to

approach conditions observed for a local ash-settling pond (Freeman

and Birge, 1978). Also, the detention time was in good agreement

with times reported for a number of TVA ash ponds (Chu, Ruane,

and Steiner, 1976). Influent and effluent water samples were taken

at 1- to 2-day intervals for 2000 hr of continuous operation to

observe changes in water-quality parameters. Determinations were

made on pH, conductivity, alkalinity, and total dissolved solids, and
AQUATIC TOXICOLOGY OF TRACE ELEMENTS 223

analyses were performed for seven selected metals (Ag, Al, Cd, Cu,

Hg, Ni, and Zn). Alkalinity and total dissolved solids were determined according to standard methods (American Public Health

Association, 1975), and metals were analyzed by atomic absorption

spectrophotometry. Fly ash displayed good settling characteristics,

and effluent water was essentially free of ash participates. The fly-ash

bed compacted sufficiently to impede interstitial percolation, limiting water movement primarily to surface flow. Through the first 770

hr of operation, influent water was distilled and deionized and had a

conductivity less than 0.25 jumhos/cm and a pH of 6.8. Total

dissolved solids and trace metals were not detectable. During the

remainder of the leaching period, the settling chamber was supplied

with carbon-filtered tap water, which had a pH of 7.1 to 7.9,

conductivity of 141 to 252 jumhos/cm, alkalinity of 54 to 70 ppm

CaCO3, and total dissolved solids of 0.19 to 0.24 g/liter. Water

temperatures ranged from 24.4 to 26.0°C.

Bioassay Monitoring of Fly-Ash Effluent

Continuous-flow bioassays were performed on the simulated ash

effluent to evaluate toxicological properties of the aqueous leachates.

Eggs of the goldfish (Carassius auratus), redear sunfish (Lepomis

microlophus), leopard frog (Rana pipiens), and Fowler's toad (Bufo

fowleri) were used as test organisms. Full-strength effluent and serial

dilutions thereof were perfused continuously through 300-ml egg

chambers at flow rates of 200 to 300 ml/hr. Effluent dilutions of

0.1, 0.01, 0.001, and 0.0001 were achieved with a proportional

diluter (Freeman and Birge, 1978). Exposure was maintained from

fertilization through hatching, and results were expressed as percent

survival (hatchability). Hatching times averaged 1.5 days for Fowler's

toad, 2.5 days for the leopard frog, and 3 days for sunfish and

goldfish. Minimum sample size was set at 100 eggs. Control egg

chambers received the same influent water as that supplied to the

simulated ash-settling pond. Bioassays were initiated after 522, 1033,

and 1775 hr of continuous aqueous leaching of the original 52-kg

fly-ash sample.

RESULTS

Embryo-Larval Bioassays

Fish and amphibian eggs were exposed to each of 22 selecte

coal elements (Table 1) from fertilization through 4 days pos

hatching, giving treatment periods of 28 days for trout and 7 da\

for the narrow-mouthed toad and goldfish. Probit-derived LC? 0 an.
224 BIRGE

LCj values expressed in parts per million and parts per billion,

respectively, are summarized in Table 2. In order of decreasing

toxicity, on the basis of LCSO determinations, the 12 elements most

lethal to trout were Hg, Ag, La, Ge, Ni, Cu, Cd, V, Tl, Pb, Cr, and Sr.

The LCSO values were 0.005, 0.01, and 0.02 for Hg, Ag, and La,

respectively; 0.05 for Ge and Ni; 0.09 for Cu; 0.13 for Cd; and 0.16

to 0.20 for V, Tl, Pb, Cr, and Sr. The calculated LC, 's for the

more toxic elements were 0.2 for Hg and Ag, 0.4 for Ge, 0.6 for Ni,

0.8 for La, 1.8 for Cu, 2.5 for Pb, and 6.0 to 6.1 for Sr and Cd

(Table 2).

The goldfish was the least sensitive of the three test species. The

12 elements most toxic to goldfish eggs were Ag, Hg, Al, Cd, As, Cr,

Co, Pb, Ni, Sn, Zn, and V. The LC50 values were 0.03, 0.12, 0.15,

0.17, 0.49, 0.66, 0.81, and 1.66 for the first eight, respectively; 2.14

for Ni and Sn; 2.54 for Zn; and 4.60 for V. The LCj values obtained

for these metals ranged from as low as 0.4 and 0.6 ppb for Al and Ag

to 400 ppb for Zn. Certain coal elements (e.g., Ag and Hg) were

more toxic to fish embryos; others (e.g., Al, Cd, Ge, and Pb)

exhibited considerable toxicity to posthatched juveniles.

In bioassays with the narrow-mouthed toad, the 12 most lethal

elements were Hg, Ag, Zn, Cr, Pb, Cd, Cu, As, Ge, Co, Ni, and Al.

The LC50 values were 0.001, 0.01, 0.01, and 0.03 ppm for the first

four elements, respectively; 0.04 ppm for Pb, Cd, Cu, and As; and

0.05 ppm for Ge, Co, Ni, and Al. The calculated LCj 's ranged

only from 0.1 and 0.6 ppb for Hg and Ag to 1.6 and 3.2 ppb for Cd

and Pb.

The LCS o values were averaged for all animal species (Table 3) to

provide a simplified toxicological index for the 22 elements. This

mean toxicity index provided a convenient ranking, consisting of

three general toxicity groups. Group 1 included ten highly toxic

elements with mean LC50 values below 1 ppm; group 2 included

nine elements with LC5 0 values of 1 to 5 ppm; and group 3 included

three elements with an LC5 0 range of 20 to 47 ppm.

The selected coal elements were also ranked according to a most

sensitive species index (Table 3) based on median lethal concentrations determined for the animal species exhibiting highest sensitivity

to each of the 22 elements. The LC5 0 values ranged from 0.001 ppm

Hg to 2.90 ppm W. Elements with approximately the same LC5 0

concentration were further differentiated on the basis of LCi values.

Aqueous Leaching of Fly Ash

A 52-kg sample of precipitator-collected fly ash was subjected to

continuous washing for 2000 hr at a flow rate of 1 liter'hr.
AQUATIC TOXICOLOGY OF TRACE ELEMENTS

TABLE 2

COAL-ELEMENT LC, ANDLC5 0 VALUES

WITH 95% CONFIDENCE LIMITS

Element

and

animal species

Aluminum

Trout

Goldfish

Toad

Antimony

Trout

Goldfish

Toad

Arsenic

Trout

Goldfish

Toad

Cadmium

Trout

Goldfish

Toad

Chromium

Trout

Goldfish

Toad

Cobalt

Trout

Goldfish

Toad

Copper

Trout

Goldfish

Toad

Germanium

Trout

Goldfish

Toad

Lanthanum

Trout

Goldfish

Toad

Lead

Trout

Goldfish

Toad

Manganese

Trout

Goldfish

I'oad

. _ Confidence limit _ c

ppm

0.56

0.15

0.05

0.58

11.3

0.30

0.54

0.49

0.04

0.13

0.17

0.04

0.18

0.66

0.03

0.47

0.81

0.05

0.09

5.20

0.04

0.05

5.60

0.05

0.02

60.4

0.29

0.18

1.66

0.0-1

2.91

*v22

I -12

Lower

0.40

0.02

0.04

0.34

3.99

0.18

0.42

0.39

0.02

0.10

0.13

0.03

0.07

0.40

0.03

0.38

0.27

0.02

0.05

4.13

0.03

0.03

1.76

0.03

0.01

30.3

0.19

0.10

0.85

0.02

1.N5

2.39

0 ,-1 \

Upper

0.70

0.82

0.08

0.92

55.0

0.51

0.67

0.61

0.07

0.18

0.21

0.05

0.31

1.10

0.04

0.58

2.27

0.08

0.15

6.41

0.05

0.07

7.84

0.08

0.0-1

105

0.43

0.32

3.05

0.07

1.37

2-1.6

2 !D

ppb

256

0.4

2.3

28.6

111

3.8

39.7

15.5

1.6

6.1

15.0

1.6

19.1

8.1

1.0

34.2

6.8

0.9

1.8

299

1.0

0.4

143

1.2

0.8

1987

7.5

2.5

14.6

3.2

3hb

2 1 . :>

'} 0

Confidence limit

-\- Lower

52.7

0.0

0.7

4.6

0.1

0.7

15.5

7.5

0.2

1.8

4.4

0.9

0.4

1.5

0.6

13.8

0.0

0.3

1.0

101

0.3

0.1

2.7

0 1

0.0

136

2.3

U.2

1.4

0.1

66 2

0 1

: ' ~

Upper

371

5.6

4.8

72.2

663

10.7

71.6

26.6

4.4

12.9

19.2

2.5

56.5

22.1

1.5

60.8

42.6

2.0

4.5

571

1.3

0

567

3>

2 7

6503

16.2

8.!

53.1

9.1

800

I h 2

9 X
226 BIRGE

TABLE 2 (Continued)

Element

and

animal species

Mercury

Trout

Goldfish

Toad

Molybdenum

Trout

Goldfish

Toad

Nickel

Trout

Goldfish

Toad

Selenium

Trout

Goldfish

Toad

Silver

Trout

Goldfish

Toad

Strontium

Trout

Goldfish

Toad

Thallium

Trout

Goldfish

Toad

Tin

Trout

Goldfish

Toad

Tungsten

Trout

Goldfish

Toad

Vanadium

Trout

Goldfish

Toad

Zinc

Trout

Goldfish

Toad

j _, Confidence limit

ppm

0.005

0.12

0.001

0.73

60.0

0.96

0.05

2.14

0.05

4.18

8.78

0.09

0.01

0.03

0.01

0.20

8.58

0.16

0.17

7.00

0.11

0.40

2.14

0.09

15.61

120

2.90

0.16

4.60

0.25

1.06

2.54

0,01

Lower

0.004

0.10

0.001

0.30

7.94

0.58

0.04

1.19

0.03

2.82

7.23

0.08

0.01

0.02

0.01

0.10

2.11

0.12

0.09

1.94

0.09

0.23

0.36

0.08

6.71

92.3

2.44

0.07

0.51

0.13

0.75

1.59

0.01

Upper

0.005

0.14

0.002

1.40

92.2

1.60

0.06

3.63

0.09

5.82

10.6

0.15

0.02

0.03

0.03

0.38

21.2

0.21

0.30

9.96

0.14

0.67

3.45

0.13

31.98

156

3.50

0.30

9.10

0.44

1.39

4.18

0.04

LC,,

ppb

0.2

14.3

0.1

22.3

39.3

3.1

0.6

55.8

0.4

79.5

506

5.0

0.2

0.6

0.6

6.0

45.3

2.4

8.4

52.5

2.4

15.5

68.8

1.7

828

345

10.7

6.9

55.2

7.4

20.0

400

0.6

Confidence limit

Lower

0.1

8.2

0.0

1.2

0.9

0.6

0.2

7.9

0.0

17.5

267

0.7

0.1

0.4

0.0

0.3

0.0

1.0

0.7

1.1

1.1

2.1

0.0

0.3

14.2

4.7

4.5

0.3

0.0

0.6

5.7

26.5

0.0

Upper

0.3

21.2

0.3

83.4

261

9.5

1.2

160

1.5

202

805

7.3

0.4

0.9

2.0

19.9

396

4.6

24.8

266

4.5

42.5

390

4.5

2810

2139

21.2

22.8

116

23.0

33.2

500

2.2
AQUATIC TOXICOLOGY OF TRACE ELEMENTS 227

TABLE 3

COMPARATIVE TOXICITY OF COAL

ELEMENTS TO FISH AND AMPHIBIAN

EMBRYO-LARVAL STAGES

Mean toxieity index* Most sensitive species index

Element

Toxicity group 1

Silver

Mercury

Cadmium

Aluminum

Cobalt

Arsenic

Chromium

Lead

Nickel

Tin

Toxicity group 2

Zinc

Vanadium

Copper

Germanium

Thallium

Strontium

Antimony

Manganese

Selenium

Toxicity group 3

Lanthanum

Molybdenum

Tungsten

LCso,

ppm Element

0.02

0.04

0.11

0.25

0.29

0.36

0.45

0.62

0.75

0.88

1.20

1.67

1.78

1.90

2.43

2.98

4.07

4.18

4.35

20.25

20.56

47.17

Mercury

Silver

Zinc

Lanthanum

Chromium

Copper

Cadmium

Arsenic

Lead

Nickel

Cobalt

Germanium

Aluminum

Tin

Selenium

Thallium

Strontium

Vanadium

Antimony

Molybdenum

Manganese

Tungsten

Species

Toad

Trout

Toad

Trout

Toad

Toad

Toad

Toad

Toad

Trout

Toad

Toad

Toad

Toad

Toad

Toad

Toad

Trout

Toad

Trout

Toad

Toad

LCso,

ppm

0.001

0.01

0.01

0.02

0.03

0.04

0.04

0.04

0.04

0.05

0.05

0.05

0.05

0.09

0.09

0.11

0.16

0.16

0.30

0.73

1.42

2.90

LC,,

ppb

0.1

0.2

0.6

0.8

1.0

1.0

1.6

1.6

3.2

0.6

0.9

1.2

2.3

1.7

5.0

2.4

2.4

6.9

3.8

22.3

3.0

10.7

*LC5o values at 4 days posthatching averaged for three species,

narrow-mouthed toad, goldfish, and rainbow trout.

Detention time was 42 hr, and water-quality parameters were plotted

and averaged for each of four 500-hr elution intervals. Total

dissolved solids, conductivity, and pH showed marked decreases

during the first 100 hr of elution time {Fig. 1). Total dissolved

solids decreased from 2.2 g/liter at 18 hr to 0.5 g/liter at 94 hr,

averaging 0.56 g/liter for the first 500 hr. Conductivity (jUmhos)

decreased from 2400 at 20 hr to 900 at 94 hr and continued to drop

slowly to 200 at 500 hr. The sharpest decline was observed for pH,

which decreased from 7.7 at 1 hr to about 4.0 at 18 hr, averaging 4.3
228 BIRGE

8.0

,pH

A , Total dissolved solids

• , Conductivity

100 200 300

FLY ASH LEACHING TIME, hr

400 500

0.0

Fig. 1 Changes in fly-ash effluent with leaching time.

for the first elution interval. As seen in Fig. 1, changes in these

effluent parameters were most pronounced during the initial 4 days

of ash-leaching time, presumably correlating with the period during

which leachable components were most rapidly removed from the fly

ash. Mean, values for the first 500 hr are given in Table 4.

Midway in the second elution interval, at 770 hr, the influent

• source was changed to carbon-filtered tap water. This action was

taken to determine whether influent water of higher pH and greater

buffering capacity would alter the leaching process. Initially,

conductivity and total dissolved solids of the effluent rose proportionately with increases observed for the new influent water, but

values for these parameters declined steadily over the third and

fourth elution intervals, closely approaching those obtained for

influent water by 2000 hr (see Materials and Methods section). After

the change to influent tap water, effluent pH for the second elution

interval increased steadily from 4.5 to 7.1. A gradual increase

continued thereafter, and, during the last two elution intervals, pH

ranges of 7.1 to 7.9 and 7.0 to 7.7 were recorded for influent and

effluent water, respectively. Although total alkalinity was not

determined during the first 1000 hr, ranges for the third and fourth

elution intervals were 32 to 55 and 46 to 62 ppm CaCO3, compared

with 54 to 69 ppm for influent tap water. After 2000 hr of

continuous washing of the original fly-ash sample, influent and
AQUATIC TOXICOLOGY OF TRACE ELEMENTS 229

TABLE 4

CHARACTERISTICS OF SIMULATED ASH-POND EFFLUENT

Characteristic Simulated effluent* TVA range*

Total dissolved solids, g/liter

pH

Conductivity, /jmhos/cm

Alkalinity, $ mg/liter CaCO3

Ag, Mg/liter

Al, mg/liter

Cd, Mg/liter

Cu, Mg/liter

Hg, Mg/liter

Ni, Mg/liter

Zn, Mg/liter

Input, ml/hr

Output, ml/hr

% evaporation

0.56 ±0.17

4.3 ±0.1

690 + 80

43 + 3

2.1 ± 0.9

32.6 + 6.1

156 + 35

110 + 26

1.8 + 0.5

155 ±16

350 ± 33

969 + 10

897 + 18

8 + 2

0.14—0.52

4.4—11.3

242—855

40—154

1.4-7.2

1-37

10—310

0.2-38

31—1100

30—1510

*Mean ± standard error for initial 500 hr of continuous operation.

tRange of mean values for 14 TVA ash ponds (Chu, Ruane, and Steiner,

1976).

I Alkalinity determined for the third 500-hr elution interval.

effluent water did not differ substantially in pH, alkalinity, conductivity, or total dissolved solids.

Effluent concentrations for the seven selected metals monitored

through 1500 hr are summarized in Table 5. Maximum concentrations, which in most instances were observed during the first 100 hr

of elution time, were 126 ppm Al, 766 ppb Zn, 518 ppb Cu, 500 ppb

Cd, 370 ppb Ni, 87 ppb Hg, and 8 ppb Ag. Mean concentrations for

the first 500 hours were 32.6 ppm Al, 350 ppb Zn, 156 ppb Cd, 155

ppb Ni, 110 ppb Cu, 2.1 ppb Ag, and 1.8 ppb Hg. The 500-hr elutior

patterns for Al, Cu, Ni, and Zn are illustrated in Fig. 2. Elevaf

concentrations observed at about 300 hr correlated with mechanic

disturbances that temporarily facilitated water filtration through the

fly-ash bed. Concentrations for all metals except mercury continued

to decline progressively with further leaching time, resulting in mean

values for the third elution interval of 540 ppb Al, 61.4 ppb Zn, 33.6

ppb Ni, 25.7 ppb Cd, 4.1 ppb Cu, and 0.2 ppb Ag (Table 5). Mercun.

fluctuated from 0.3 to 7.4 ppb during the first 500 hr but increasei

substantially thereafter, with mean values of 27.4 and 14.9 ppb fo<

the second and third elution intervals. However, the mercury levei

dropped markedly toward the end of the third elution period,

averaging 2.6 + 0.7 ppb after 1360 hr. Metals were not detected ir
23d BIRGE

TABLE 5

METAL CONCENTRATIONS FOR FLY-ASH EFFLUENT

Element

Ag

Al

Cd

Cu

Hg

Ni

Zn

Maximum

tration, ppb

8

126,000

500

518

87

370

766

Mean concentration for three elution intervals, ppb*

0—500 hr

2.1 ±0.9

32,600 + 6,100

156 ± 35

110+ 26

1.8 ±0.5

155 + 16

350 + 33

500—1000 hr

0.2 + 0.2

1,570 ±260

93.8 + 24.8

14 + 1.8

27.4 + 11.7

58 + 10

106 ± 20

1000— 1500 hr

0.2 + 0.2

540 + 80

25.7 ± 11.3

4.1 ± 0.8

14.9 + 5.3

33.6 + 2.3

61.4 +4.1

Influent

concentration, ppb

0.0

230 ± 29

1.7 + 0.8

3.5 ± 0.9

0.0

3.3 + 1.4

4.9 + 3.1

*Mean values with standard errors were based on analyses taken at 1- to 3-day intervals.

100 200 300

FLY ASH LEACHING TIME, hr

400 500

Fig. 2 Leaching patterns for fly-ash metals.

the distilled—deionized influent water used for the first 770 hr, and

background values for the carbon-filtered tap water are given in

Table 5.

Bioassay Analysis of Fly-Ash Effluent

Four sets of embryo—larval bioassays were performed on fly-ash

effluent by use of a continuous-flow system. Tests were initiated
AQUATIC TOXICOLOGY OF TRACE ELEMENTS 231

after 522, 1033, and 1775 hr of continuous aqueous leaching of the

original 52-kg sample of precipitator-collected fly ash. At 522 hr

tests were conducted on eggs of the leopard frog and Fowler's toad

with undiluted ash effluent. Prog eggs suffered rapid and complete

mortality, and a hatching frequency of 46% was observed for

Fowler's toad. Survival was 97 to 99% for control populations

treated with the same influent water source used to supply the flyash leaching chamber (Table 6). Bioassays were initiated at 1033 hr

on eggs of the redear sunfish. Undiluted effluent produced complete

mortality, and 0.1 and 0.01 dilutions gave survival frequencies of 42

and 90%, which closely approached control survival. In tests with

goldfish eggs conducted at 1775 hr, survival averaged 57, 76, and

88% for undiluted effluent and 0.1 and 0.01 dilutions, respectively.

Control survival was 92%.

Effluent metal concentrations observed for the amphibian

bioassays approximated mean values given for the second elution

interval (Table 5). Although ash toxicants produced a near-LC50

response for toad eggs, the exposure period was limited to only 1.5

days. In addition, developmental stages of Fowler's toad are highly

resistant to trace metals, compared with other amphibian and piscine

species (Birge, 1976). Animal species used for the initial toxicological

TABLE 6

EMBRYO-LARVAL BIOASSAYS ON FLY-ASH EFFLUENT

Species

Leopard frog

(Rana pipiens)

Fowler's toad

(Bufo fowleri)

Redear sunfish

(Lepomix

microlophux)

Goldfish

(Carasxius

aura tun)

Elution

interval,

hr

522-582

522-558

1033—1105

1775-1847

Exposure

time,

days

2.5

1.5

3.0

3.0

Bioassay

solution

Ash effluent

Control

Ash effluent

Control

Ash effluent

Diluted effluent

0.1

0.01

0.001

0.0001

Control

Ash effluent

Diluted effluent

0.1

0.01

Control

Percent

survival

at hatching

0

97

46

99

0

42

90

93

95

89

57

76

88

92
232 BIRGE

characterization of coal elements were not available for the first two

sets of effluent bioassays. Sunfish eggs, however, have the same

hatching time (exposure period) as goldfish and generally exhibit

similar sensitivity when used in aquatic bioassays (Birge, Black,

and Westerman, 1978). During the exposure period for sunfish eggs,

mean effluent metal concentrations, with standard errors, were

0.4 ± 0.2 ppb Ag, 1070 ± 230 ppb Al, 72.0 ± 43.0 ppb Cd, 5.5 ± 1.8

ppb Cu, 20.6 ± 4.8 ppb Hg, 31.5 ± 1.4 ppb Ni, and 70.0 ± 6.7 ppb

Zn. At the 0.1 dilution, which gave 42% survival for sunfish eggs

(Table 6), all analyzed metals except aluminum were well below

goldfish LC! values. Aluminum was present at approximately

two-thirds of the LCSO value. Although the effluent was not

analyzed for all possible toxicants, this correlation tends to support

application of the toxicological index given for coal elements

(Tables 2 and 3). Before the goldfish bioassays were initiated,

effluent metal concentrations had dropped to 0 ppb Ag, 160 ± 10

ppb Al, 1.5 ±1.5 ppb Cd, 4.5 ± 1.8 ppb Cu, 3.8 ± 0.7 ppb Hg,

23.0 ± 3.0 ppb Ni, and 44.5 ± 8.0 ppb Zn. These values were all

below LCi 's calculated for goldfish, except aluminum, which was

present at about the LC50 level (Table 2). The undiluted effluent

gave 57% survival.

DISCUSSION

The embryo—larval bioassays reported in Table 2 demonstrate

'the high toxicity of numerous inorganic coal elements to aquatic

biota. Depending on the animal species, LC50 values of 0.1 ppm or

less were observed for 15 coal elements, and calculated LC] 's

ranged down, to 0.1 to 0.2 ppb for mercury and silver. Tungsten was

the least toxic element in all cases, with LC50 values ranging from

2.90 ppm for the toad to 120 ppm for the goldfish. When the test

1

 data were averaged, the increasing order of sensitivity of animal

species was goldfish, trout, and toad.

The order of toxicity of the 22 elements, as determined by LC50

values, varied somewhat for embryo—larval stages of the three

species. Only Ag, Cd, Cr, Hg, Ni, and Pb occurred among the 12 most

toxic elements for all three, but Al, As, Co, Cu, Ge, V, and Zn were

included in this group for two species (Table 2). Of particular

interest were the consistent extreme toxicity of mercury and silver to

developmental stages of all species and certain selective responses,

such as the high relative toxicity of aluminum to goldfish, germanium and lanthanum to trout, and selenium and zinc to the toad.
AQUATIC TOXICOLOGY OF TRACE ELEMENTS 233

100 H£

0 -

0.0001 0.001 0.01 0.1

SILVER CONCENTRATION, ppm

Fig. 3 Effects of silver on embryo—larval stages.

1.0

Several patterns of response were discernible concerning the

differential sensitivity of the three test organisms. Highest uniformity

was obtained for silver, which gave an exceptionally narrow range of

LC50 values (0.01 to 0.03 ppm). As seen in Fig. 3, this relationship

held for the full range of exposure concentrations. Germanium

produced similar effects on the two most sensitive test animals, trout

and toads, but was substantially less toxic to the goldfish (Fig. 4).

This same pattern was given by Cu, Mo, Ni, Sb, Sr, Tl, and V. A still

more heterogeneous response occurred for Pb (Fig. 5), Hg, and

certain other elements (e.g., La, Sn, and W). Considering the response

patterns summarized in Figs. 3 to 5, it is probable that the diversity of

aquatic species affected by pollution would increase in the order of

Pb, Ge, and Ag. Although elements such as Pb and Ge likely

would affect fewer species, these toxicants probably would contribute to an ecological imbalance of aquatic biota. As noted, Se,

Zn, and certain other elements (e.g., As and Co) were more selective

for the toad, and, on the basis of LC5 0 values, the toad was the most

sensitive species for 17 of the 22 elements. This suggests that

amphibians may constitute particularly sensitive target sites for cord

contaminants. For example, goldfish LCS (l determinations for

selenium and zinc exceeded those for the toad about 100 and 250

times, respectively.
234 BIRGE

0 -

0.001 0.01 0.1 1

GERMANIUM CONCENTRATION, ppm

Fig. 4 Effects of germanium on embryo—larval stages.

100

100

0 -I

0.001 0.01 0.1 1

LEAD CONCENTRATION, ppm

100

Fig. 5 Effects of lead on embryo—larval stages.
AQUATIC TOXICOLOGY OF TRACE ELEMENTS 235

The heterogeneity of response observed for the three animal

species somewhat complicates application of the bioassay data on

coal elements to impact assessment and pollution-abatement technology. Therefore, the mean LCS 0 and sensitive species indexes

(Table 3) were developed to provide a simplified data base for energy

and environmental engineers. The sensitive-species ranking for coal

elements was used to delineate upper limits of toxicity observed for

the 66 independent bioassays, and the mean index summarized

average test responses. Despite some notable exceptions (e.g., Al and

La), the toxicological orders given in the two indexes were generally

similar. Principal differences in relative order were attributed to

elements exhibiting disproportionate selective toxicity for a particular animal species. The only extreme disparity involved lanthanum,

for which mean and sensitive species LC50 values differed by three

orders of magnitude. We should note that several recent publications

review additional bioassay data for some of the trace metals found in

coal (National Academy of Sciences—National Academy of Engineering, Committee, 1973; Vaughan et al., 1975; Environmental Protection Agency, 1976).

In the fly-ash leaching study, characteristics of the simulated

effluent were compared with those recorded for 14 TVA ash ponds.

As seen in Table 4, good agreement was obtained for all test

parameters except aluminum and cadmium, but concentrations for

these metals were within TVA ranges early in the third elution

interval. The high initial values for aluminum and cadmium may have

resulted from use of distilled influent water, which contributed to

low pH in the simulated ash pond. These and other results indicate

that the quality of effluent water may be improved somewhat by

regulating certain parameters (e.g., pH and alkalinity) of influent

water used for ash sluicing.

Appreciable metal leaching continued, however, even after 770

hr, when the change was made in influent water (Table 5). The

resulting suite of toxic metals produced lethality of test organisms

through 1775 to 1847 hr of continuous elution time (Table 6).

Effluent metal concentrations (Table 5) were compared to freshwater guidelines (National Academy of Sciences—National Academy

of Engineering, Committee, 1973; Environmental Protection Agency,

1976) to further evaluate potential effects of fly-ash leaching on

aquatic biota. Through 1775 hr, mercury remained well above the

limit of 0.05 ppb, and aluminum exceeded the 100-ppb level

considered deleterious to growth and survival of fish. Cadmium was

over the trout standard of 0.4 to 1.2 ppb for 1775 hr and exceeded

the maximum limit for other aquatic species (4 to 12 ppb) for 1050
236 BIRGE

to 1435 hr. On the basis of the Environmental Protection Agency's

(EPA) application factor (0.01) and the trout, toad, and goldfish

embryo—larval LCS 0 values, nickel and zinc concentrations exceeded

recommended levels for all test species through 1775 hr, and silver

was above acceptable limits for 1050 to 1266 hr. Copper, with an

application factor of 0.1, exceeded calculated concentrations for

trout and toad through 1000 to 1500 hr but was over the goldfish

limit for only 22 hr. Using embryo—larval rather than adult LCSO

values resulted in more stringent limits for Ag, Cu, Ni, and Zn.

However, freshwater standards should permit adequate protection

for sensitive life-cycle stages. Except for copper, the suggested EPA

application factors appeared acceptable for embryo—larval stages. On

the basis of data in Table 2, 0.01 to 0.05 of LC5 0 determinations

gave values that generally fell within or near 95% confidence limits

for LC, 's. In comparison with the EPA value of 0.1, a more suitable

application factor for copper was found to be 0.05 for goldfish and

trout and 0.01 for the toad.

Since combined toxicological effects of complex suites of trace

metals are difficult to quantify by existing hazard-assessment criteria,

direct bioassay monitoring was used to provide further characterization of ash effluent. As noted, after 1033 hr of continuous elution,

undiluted ash effluent produced 100% mortality of sunfish eggs, and

survival of goldfish eggs was reduced to 57% when exposure was

initiated at 1775 hr. A 0.1 dilution produced an approximate LC50

for sunfish, and 0.01 gave essentially control-level survival for both

species. When median survival was obtained, concentrations of all

monitored metals except aluminum were at or below goldfish LCj

values, and aluminum was present at about the LC50 level (Table 2).

Effluent dilutions that gave control-level survival did not contain any

monitored metals at concentrations exceeding goldfish LC] values.

Although ash effluent was not analyzed for all possible toxicants,

results obtained by direct effluent monitoring were in good

agreement with the independent embryo—larval bioassays for coal

elements. Also, trace metals present at or below the probit LCi 's did

not exert any overt synergistic effects. In addition, results indicate

that continuous-flow embryo—larval test systems are highly suitable

for in situ toxicological monitoring of complex coal effluents.

Although not intended to serve in lieu of actual field studies,

simulated ash ponds can be used to characterize aqueous leaching

processes and to evaluate ash effluents for potential environmental

hazards. Test parameters can be manipulated individually to determine effects on metal elution rates, and such model systems can be

particularly useful in comparing ash residues of coal from different
AQUATIC TOXICOLOGY OF TRACE ELEMENTS 237

formations. The chemical composition of bottom and fly ash is

highly variable, depending on the source of the coal used, combustion conditions, and such factors as the efficiency of emission -

control equipment (Moulton, 1973; Chu, Nicholas, and Ruane, 1975;

Cooper, 1975). In addition to differences in ash composition,

numerous physical and chemical factors may affect the leaching of

trace elements and the final composition of ash-pond water. These

factors include the quantity of water used for sluicing; its temperature, pH, and hardness; and various performance characteristics of

the settling pond. As noted by Chu, Nicholas, and Ruane (1975), the

effects of such variables on the quality of ash-pond effluents are not

sufficiently understood. It is known, however, that a number of

coal-derived inorganic elements reach appreciable concentrations in

ash-pond waters. Since 1973, TVA has analyzed for 17 trace

elements in quarterly grab samples from bottom ash, fly ash, and

combined ash ponds, and the results have been summarized by Chu

and co-workers (Chu, Nicholas, and Ruane, 1975; Chu, Krenkel, and

Ruane, 1976). Discharges from fly-ash ponds were reported to

contain up to 7.3 ppm Al, 0.3 ppm Ba, 0.04 ppm Cd, 0.1 ppm Cr,

0.3 ppm Cu, 0.08 ppm Pb, 13.4 ppm Mn, 1.1 ppm Ni, and 1.5 ppm

Zn. Ranges for a number of these metals are summarized in Table 4.

Other investigators also have considered various problems

associated with fly-ash disposal (Guthrie, Cherry, and Rodgers, 1974;

Theis, 1975: Holland et al., 1975). Theis (1975) indicated that the

production of metal leachates and alterations of pH and dissolved

oxygen may affect receiving waters. He also demonstrated significant

release rates for trace metals when fly ash was dispersed in distilled

water. Holland et al. (1975) investigated the environmental effects of

trace elements in the pond disposal of ash and flue-gas desulfurization sludge. Samples of ash and sludge from five generating stations

were studied by simulated ponding. In general, concentrations of

aqueous leachates were low, but Ba, B, Cr, Hg, and Se exceeded EPA

guidelines for public water supplies. However, these investigators did

not compare their findings with EPA standards for freshwater biota,

which generally are more stringent, and they did not consider the

combined toxic effects of the resulting metal mixtures. Guthrie,

Cherry, and Rodgers (1974) evaluated the impact on biota in

waters receiving ash-basin effluent from a coal-fired power plant.

Bacterial, plant, and animal diversities were reduced at sites affected

by ash effluents. Abiotic water parameters affected by ash-basin

effluents included temperature, turbidity, dissolved oxygen, and pH.

Concentrations of coal-ash leachates (e.g., Cd, Cr. Cu, Hg, and Zn)

were lowest in effluent water, somewhat greater in aquatic biota, and
238 BIRGE

highest in benthos. This indicated accumulation of these toxicants in

biomass and bottom sediment.

The results given here show clearly that a substantial number of

minor and trace elements of coal and fly ash are highly toxic to

aquatic organisms. Many are leachable from ash residues at concentrations that prove lethal to fish and amphibian embryo—larval stages

and other organisms. Since annual coal utilization in the United

States may reach 1 billion tons or more in the near future (Vaughan

et al., 1975), it remains essential to characterize more fully the toxic

properties of coal-derived contaminants, ascertain their release rates,

and determine their pathways of exchange within and ultimate

effects upon aquatic ecosystems.

ACKNOWLEDGMENTS

I should like to acknowledge efforts devoted to bioassay

evaluation by A. G. Westerman and J. A. Black and contributions by

R. A. Freeman and J. E. Hudson to the fly-ash-leaching studies. I am

most grateful to B. A. Ramey for preparation of the manuscript and

figures. The research reported here was supported by the Institute

for Mining and Minerals Research, Lexington, Kentucky (grant

number 7576-EZ).

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