ABSTRACT
Disposal of coal fly ash in soil-capped landfills has raised questions regarding the presence of potentially toxic elements in the ash and their future disposition in the local ecosystem. Experiments were carried out on the uptake of chemical elements by cultivated and indigenous plants grown on a coal fly ash landfill and on control sites. Selenium was found to concentrate in amounts more than 50 times higher in landfill-grown plants than in control plants, and was the element of greatest interest and concern. Other elements, such as Mo and B, were often higher in the tissues of control plants, but the degree of uptake was usually less than two-fold.
Rutabaga (Brassica napus L., Cruciferae), birdsfoot trefoil (Lotus corniculatus L., Leguminoseae), and alfalfa (Medicago sativa L., Leguminoseae) absorbed more Se than other species such as carrot (Daucus carota L., Umbelliferae), corn (Zea mays L., Graminae), timothy (Phleum pratense L., Graminae), bromegrass (Bromus inermis Leyss, Graminae), red clover (Trifolium pratense L., Leguminoseae), or milkweed (Asclepias syriaca L., Asclepiadaceae). Cauline leaves of wild carrot and bitterweed (Picris hieracioides L., Compositeae) contained more Se than older rosette leaves. In sweet and field corn cultivars, greater amounts of Se were found in leaves and kernels than in stems, cobs, or roots.
Coal flue gas desulfurization will result in the production of CaSO3 as a byproduct, from which gypsum (CaSO4) can be made easily. Research by others indicated that application of gypsum to Se-containing soils often resulted in reduced Se uptake in plants. In the studies described here, application of gypsum at the rate of 2 metric tons/ha reduced the uptake of Se in both rutabaga and carrot shoots and roots. We conclude that gypsum application offers a possible management tool to control uptake and cycling of Se through plants to other biota.
