Effect of low concentrations of phosphate ions on extraction of arsenic from naturally contaminated soil.

The effect of low concentrations of phosphate ions on the extraction of arsenic (As) was tested on naturally contaminated soil (As 126 mg/kg) using batch experiments. Interaction entails the extraction of low concentrations of As (5.4-23.3 microg/L As). There are statistical differences in the contents of As, Ca, Cu, Ni, Pb and nitrate in the composition of the extracts. Three types of kinetic curves document that dissolution and precipitation reactions, adsorption, desorption and biological processes participate in determining the composition of the extracts. The elevated As contents in the phosphate extracts are probably caused by competition between phosphate and arsenate ions for soil adsorption sites.