Trace element solubility from land application of fly ash/organic waste mixtures with emphasis on arsenic and selenium speciation

Mixing of coal fly ash with organic wastes to provide balanced soil amendments offers a potential viable utilization of this industrial by-product; however, trace element solubility needs to be evaluated. Soil solution speciation of As and Se from fly ash/organic waste mixtures is also of environmental concern. Coupling of ion chromatography with inductively coupled plasma mass spectrometry (IC-ICP-MS) has proved an effective method for determining As speciation at trace concentrations; however, ICP-MS has not previously been used for multi-element detection in As and Se speciation analysis. Two fly ashes mixed with either poultry litter or sewage sludge at ratios of 4:l and 2:1, respectively, were land-applied to a Cecil sandy loam at application rates of 80 Mg ha{dollar}sp{lcub}-1{rcub}{dollar} fly ash, 20 Mg ha{dollar}sp{lcub}-1{rcub}{dollar} poultry litter, and 40 Mg ha{dollar}sp{lcub}-1{rcub}{dollar} sewage sludge. Maize was planted on the amended field plots and tension lysimeters were used to collect soil solution. Increased soluble concentrations of P, C, Cu, As, Se, Mo, and Cr were determined in fly ash/poultry litter plots relative to fly ash/sewage sludge plots: Increased soluble P and organic C from the poultry litter may have increased soluble oxyanion concentrations from the fly ash. Increased soil solution concentrations were transient, decreasing to near control levels after approximately 30 days. A subsequent laboratory incubation study indicated that Cu was highly soluble from poultry litter, and that soluble Cu was highly correlated with soluble C. The poultry litter was also a significant source of soluble As. Mixing of fly ash with either organic waste increased soluble Se concentrations relative to land application of the fly ash alone. Soil solution speciation showed that Se was present as selenate, Se(VI), and increased soluble Se may have resulted from higher pH and increased sulfate concentrations of the fly ash/organic waste mixtures. Soluble As was present as As(V) in fly ash-amended soils, while dimethylarsinate (DMA) was the predominate species in fly ash/poultry litter-amended soils. IC-ICP-MS proved an effective technique for As and Se speciation analysis in environmental samples, yielding detection limits of {dollar}<{dollar}1{dollar}mu{dollar}g L{dollar}sp{lcub}-1{rcub}{dollar} for all species analyzed.