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 deter- 

 mined 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 particulates. The fly-ash 

 bed compacted sufficiently to impede interstitial percolation, limit- 

 ing 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 

 CaC03, and total dissolved solids of 0.19 to 0.24 g/hter. 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 selected 

 coal elements (Table 1) from fertilization through 4 days post- 

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

 for the narrow-mouthed toad and goldfish. Probit-derived LC50 and 



