煤灰中砷分析

Arsenic concentrations in coal fly ash are variable (depending on the source coal), but, in general, As concentrations in fly ash are higher than background soil values. Arsenic is also relatively soluble from fly ash because it occurs as a surface precipitate on the ash particles. Vast quantities (> 100 million tons) of fly ash are generated in the US annually, and most of this ash is disposed of by sluicing to ash settling basins. In this preliminary study we report on the As speciation in a series of ash settling basins at a functioning power plant on the Savannah River Site, Aiken, SC. Animals inhabiting the ash basins have been identified as having greater body burdens of As and Se than comparable animals from reference sites in the vicinity (Hopkins et al. 1998). Arsenic bioavailability depends on the prevalent speciation, which determines solubility, mobility, and toxicity; hence, by investigating As chemistry on a speciation basis we hope to better understand the biogeochemistry of As in the ash basin system. Fly ash is sluiced from the power plant to two settling beds, where initial particle settling occurs. Water flows from these beds to a primary ash basin, followed by a secondary basin then to a swamp prior to discharge into Beaver Dam Creek, which drains directly into the Savannah River (Figure 1). Residence time for basin 1 was estimated at 39 days and for basin 2 was 22 days.