University of California Water Resources Center

Solutions containing Ca, Mg, K, Na, Pb, Ni, Cd, Cr, Cu, Zn, NH4, SO4, Cl, HCO3, PO4 at concentrations that are typically encountered in wastewaters were allowed to percolate through soil columns 15 cm in diameter and 200 cm deep in two soils; San Emigdio and Superstition sands with known physical and chemical properties were used in these experiments. The analysis of the percolating waters indicated that the trace metal concentrations were attenuated to the extent of non-detectability by A.A. spectrometry. The San Emigdio soil showed greater attenuation of PO4 and NH4 in comparison with Superstition sand. Speciation calculations by using GEOCHEM indicated that the major fractions of the trace metals were in cationic form and therefore would be absorbed by the soil exchange complex. Simulations that included the presence of dissolved organics indicated that a major fraction of Cu, Ni and Zn were complexed by the organic ligands. The speciation of Cd and Pb on the other hand were mainly influenced by the inorganic ligands.