AQUATIC TOXICOLOGY OF TRACE ELEMENTS 



227 



TABLE 3 



COMPARATIVE TOXICITY OF COAL 



ELEMENTS TO FISH AND AMPHIBIAN 



EMBRYO-LARVAL STAGES 



Mean toxicity index* 



Most sensitive species index 



Element 



LC50 , 

 ppm 



Element 



Species 



LC50, 

 ppm 



LCi, 

 ppb 



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

 narrow-mouthed toad, goldfish, and rainbov^ 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 decHne was observed for pH, 

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



