224 BIRGE 



LCi 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 LC50 determinations, the 12 elements most 

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

 The LC50 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 LCj '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 v/ere 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 LCi '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 LC5 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 vidth mean LC50 values below 1 ppm; group 2 included 

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

 three elements with an LC5 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 concentra- 

 tions determined for the animal species exhibiting highest sensitivity 

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

 Hg to 2.90 ppm W. Elements with approximately the same LC^o 

 concentration were further differentiated on the basis of LCj values. 



Aqueous Leaching of Fly Ash 



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

 continuous washing for 2000 hr at a flow rate of 1 liter/hr. 



