LONG-TERM SUPPLY AND UPTAKE BY PLANTS OF ELEMENTS FROM COAL FLY-ASH

To assess the mineral composition of plants growing in pure fly ash, g rasses growing on lysimeters filled with alkaline, neutral, or acid fl y ash were sampled several times in a 6-year period. The samples were analyzed for elements essential for plants and animals as well as non- essential, but environmentally significant, trace elements. Grasses we re also sampled-from ash dumps that were 20 and 30 years old. Fly ash is not a proper source of plant macronutrients N, P, and K. Plant grow th on the alkaline fly ash can be influenced for some time by the high salinity of that ash. Grasses growing on unweathered fly ash were fou nd to be high in Al, B, Co, Fe, Mo, Ni, Pb, and Se. Concentrations of several elements declined in time but levels of B, Fe, Mo, and Ni were still elevated in grasses on both fly ash dumps. All concentrations, except Al, were lower than toxicity levels for plants as found in lite rature. In plants growing on fresh fly ash concentrations of Mo, Pb, a nd Se can exceed the maximum tolerable levels for domestic animals. On weathered fly ashes (ash dumps) the Mo, Pb, and Se concentrations in grasses were below the maximum tolerable levels. Effects on animals by Mo in weathered ash may not be excluded because Mo concentrations can be high enough to induce Cu deficiency. Animals that feed on plants g rown on fly ash could suffer from Ca, Mg, Na, and P deficiency.