Collect soils and bioassay phytoavailability o Cd, Zn and Cu in soils unamended or long-term biosolids amended soils with pH made equal, to characterize changes in the metal binding equilibria of thepaired soils, in relation to properties of the biosolids or soils.Evaluate changes in Fe or Mn oxides or humics which could cause observed changes in metal uptake. Collect soils from Pb-contaminated sites to evaluate the effect of phosphate and
Soils will be obtained from long-term field experiments with known additions of biosolids many years ago,such that solid organic carbon is near that of the controls. VT and ARS will measure phytoavailability of Cd, Zn, and Cu in biosolids amended and unamended soils, using greenhouse or growth chamber plant bioassay methods with equal pH for test soils. Soils will be evaluated for changes in hydrous Fe and Mn oxides, soil organic matter fractions, and metal solubility, EPA/Ryan will conduct absorption studies to evaluate ability of the test soils to limit the activity of free metal ions of Cd, Zn or Cu, using specific ion electrodes and Donnan dialysis. Qualitative changes in soil organic matter will be evaluated. Together, effects on adsorption will be compared with changes in soil metal phytoavailability due to biosolids additions.