PHOSPHATE FERTILIZERS INFLUENCE LEACHING OF LEAD AND ARSENIC IN A SOIL CONTAMINATED WITH LEAD ARSENATE

Use of high rates of monoammonium phosphate (MAP) or monocalcium phosphate (MCP) fertilizers has the potential to alter Pb and As mobility in soils contaminated with lead arsenate pesticide residues. A laboratory column experiment was conducted to determine the effects of P amendment source (MAP, MCP), P rate (0, 0.31, 0.62 g column-1), and amount of leaching (1, 2 pore volume displacements, PVD) on Pb, As, P, pH, and salinity distribution within the leaching from a Burch loam soil containing 1800 mg Pb kg-1 and 400 mg As kg-1. Addition of either MAP or MCP significantly increased the amount of As leached from the soil. The P amendments reduced the amount of Pb in the first PVD but enhanced Pb in the second PVD so that the cumulative amount of Pb leached was independent of treatment. Phosphorus source, P rate, and quantity of leaching water influenced the total amount of leachate As, and soil and leachate P, pH, and salinity. Use of phosphate fertilizers on lead arsenate-contaminated soils may temporarily enhance potential for As phytoavailability or As contamination of groundwater.