Soluble Arsenic and Selenium Species in Fly Ash/Organic Waste-Amended Soils Using Ion Chromatography−Inductively Coupled Plasma Mass Spectrometry

Mixing coal fly ash with an organic waste increases macronutrient content and may make land application of fly ash a viable disposal alternative. However, trace element chemistry of these mixed waste products warrants investigation. Speciation of As and Se in soil solutions of fly ash-, poultry litter- and sewage sludge-amended soils was determined over a 10-day period by ion chromatography coupled to inductively coupled plasma mass spectrometry (IC−ICP-MS). Detection limits were 0.031, 0.028, 0.051, 0.161, 0.497, and 0.660 μg L - 1 for dimethylarsinate (DMA), As(III), monomethylarsonate (MMA), As(V), Se(IV), and Se(VI), respectively (100 μL injection). Arsenic was highly water-soluble from poultry litter and appeared to be predominantly As(V). Arsenic(V) was the predominant species in soil amended with two fly ashes. Application of fly ash/poultry litter mixtures increased As solubility and led to the prevalence of DMA as the major As species. DMA concentrations in these soil solutions decreased rapidly over the sampling period relative to As(V), suggesting that DMA readily underwent mineralization in the soil solution. Se(VI) was the predominant soluble Se species in all treatments indicating rapid oxidation of Se(IV) initially solubilized from the fly ashes.