Chemical and toxicological properties of coal fly ash - University of ...

steady state conditions in the disposal pond, they may have longresidence times in the ash effluent, thus increasing the probability ofbioaccumulation by aquatic organisms.13. Of the 12 fly ash samples evaluated, five were selected for toxicitytesting on the basis of the diversity of extract pH values observed.All five extracts were acutely toxic to fathead minnow fry.14. Physicochemical components probably responsible for the acute toxicityof the fly ash extracts to fish were pH, Al, ionic strength, and Zn.Because of the complex composition of some extracts and the unknownsynergistic and antagonistic effects of the chemical constituents ofthe extracts, it was not possible from these experiments to determinewhich chemical constituents specifically were responsible for theobserved mortality.15. The fly ash extracts were diluted to levels presumed subacutely toxicfor use in bioaccu~nul at ion experiments. The growth of fathead minnowsand green sunfish exposed to these diluted fly ash extracts was notsignificantly different from that of control test organisms exposed tofiltered tap water under similar conditions.16. The fathead minnows and green sunfish accumulated similar elements fromthe fly ash extracts; the six chemical constituents most commonlyaccumulated from fly ash extracts were Al, B, Cd, Mn, Mo, and Ni. Ofthese six chemical constituents, Cd appeared to be of greatestimportance because of its highly toxic nature.1. An apparent relationship was observed between the initial pHcharacter of a fly ash leachate and its color and the matrixCaO/S03 ratio in the solid waste. Further study of the less commonlyproduced acidic high-iron fly ashes should be done.2. The long-term equilibration (LTE) extraction procedure was designed tosimulate equilibrated ash ponds. Although obtaining representative pondsamples is difficult, such field work should be done to assess theaccuracy of the LTE procedure.3. Fly ash laboratory extracts often undergo complex changes in chemistrywith time and should be studied to determine which mineral phasescontrol the aqueous solubility of the components. The chemistry ofslurry water and disposal ponds should also be studied and modeled todetermine whether the same types of changes that occur in laboratoryextracts occur in the field,4. Grab samples were collected from only nine power plants, seven of whichwere in Illinois. To provide a more complete picture of fly ashcomposition and variability, samples from other Illinois power plantsand from other states should be studied.5. The scope of the ecological analyses of fly ash in this study consistedof acute static bioassays using fathead minnow fry and bioaccumulation