TEMPORAL VARIATIONS IN TRACE METAL UPTAKE MEASURED IN PLANTS GROWN IN COAL FLY ASH AMENDED SOILS

Temporal variations in trace metal uptake were evaluated in basil, tomato, zucchini, and dwarf sunflower grown in soils amended with 5, 10, and 20% by weight of fly ash, a coal combustion byproduct that has been used as a soil amendment at reclaimed mine sites. Plants were also grown in unamended soils as a control. Stems and leaves were harvested at 4, 8, and 11 weeks of growth, and submitted for analysis by inductively coupled plasma mass spectrometry to determine trace metal uptake. Elements analyzed included Ag, As, Au, Ba, Bi, Br, Cd, Co, Cs, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Th, Tl, U, W, and Zn, which are commonly found in fly ash.

Preliminary evaluation of the data indicates that the amount of fly ash amendment does not significantly influence the concentration of most trace elements in the analyzed plants. The only elements to increase in concentration with increasing quantities of fly ash were As (particularly in basil, tomato, and zucchini), Mo (basil, tomato, and squash), and Tl (tomato, zucchini, and squash). Variations in trace element concentrations do, however, occur in plant material collected from the various harvest events. Several elements, particularly Cd, were more highly concentrated in the third cutting, suggesting continued uptake through time. Other elements, including Co and Mn, were more highly concentrated in plant material collected from the first harvest, with concentrations decreasing in subsequent harvests. This decrease in concentration over time may be related to 1) decreased availability of trace elements in the soil possibly due to removal during watering and/or 2) relocation of the trace elements to other parts of the plants that were not tested, such as fruits, flowers, or roots.