Solubility and Equilibria of Zinc in a Flooded Soil

Abstract

AbstractSoil solution composition data were obtained for flooded Crowley silt loam soil. These data were analyzed with a computer program which corrected for ion‐pair formation and computed soil solution Zn activities at 0, 50, and 90% complexation by soluble organic species. The computed values were compared to predicted soil solution Zn activities which would occur if ZnCO3(c), Zn2SiO4(c), Zn3(PO4)2·4H2O(c), or ZnS(c) were the controlling solid phase. Under flooded soil conditions, ZnS(c) was the only possible solid phase which could be controlling soil solution Zn activity, assuming that the H2S(g) pressure in the soil solution was similar to that of atmospheric air [pH2S(g) = 10.3] and that between 50 and 90% of solution Zn was complexed by organic species. Under laboratory conditions where H2S(g) levels were thought to be much lower than unpolluted air, both Zn2SiO4(c) and ZnCO3(c) appeared to be potential solid phases. Zinc phosphate, Zn3(PO4)2·4H2O,(c), was too soluble to control solution Zn in this soil.