Characterization of microbial abundance and activity from three coal ash basins

Abstract

The effects of coal ash (differing in age by the time of disposal) on the abundance of soil microorganisms, dehydrogenase activity and soil respiration were assessed. Samples of sluiced and cyclone-bottom ash from two abandoned sites, and one sluiced-ash site, currently in use, were collected at the Savannah River Site in Barnwell County, S.C. Soil samples collected near the ash basins were used as a control. There were significant differences by location in the estimates of actinomycetes, culturable bacteria, fungi, amylolytic organisms, and nitrifying, denitrifying and selenate-reducing bacteria. In general, higher estimates of actinomycetes, bacteria, fungi, amylolytic organisms and denitrifying bacteria were obtained from the abandoned sluiced-ash basin. The estimates of nitrifying and selenate-reducing bacteria were highest in the new ash basin currently in use. Microbial populations were correlated with pH, % total C, or % total N. Most of the correlations were associated with total N. Microbial diversity indices (phyleal and physiological) were determined to be low (< 1.0) for all locations. However, phyleal diversity indices also correlated with % total N. Increases in dehydrogenase activity and soil respiration were observed when ash or soil samples were treated with glucose or glucose plus ammonium nitrate, indicating that the availability of simple organic compounds and N are limiting factors for microbial activity. Cumulative CO 2 evolution indicated that a priming effect occurred by day 15 of incubation after glucose or glucose plus ammonium nitrate had been applied. The results suggest that the abundance, diversity and activity of microorganisms increase as the ash basin ages. The land-disposal of fly ash will require the addition of low C:N ratio residues to stimulate microbial community development.