EFFECT OF NITRIFICATION ON MOVEMENT OF TRACE-METALS IN SOIL COLUMNS

Soil column experiments were conducted with sludge-treated and untreated samples of two soils. Omni silty clay and Delhi loamy sand, to determine whether protons generated during the nitrification process would affect the mobility of the trace metals Cd, Cr, Cu, Mn, Pb, and Zn. Average concentrations of metals in column effluents were well below 1 ppm in all cases except Zn eluted from untreated Delhi loamy sand where 20 mM NH//4Cl or KCl leaching solutions produced effluent concentrations slightly above 1 ppm. There was evidence of nitrification affecting movement of several of the metals, particularly in the cases of Mn, Zn, Cu, and Cd in the untreated Delhi soil. The presence of sludge had a pronounced stabilizing influence of Cd and Zn, and a lesser degree on other metals, probably as a result of organo-metal complexes.