Factors affecting molybdenum sorption in soils: Potential biosolids effects

Many factors impact molybdenum (Mo) retention and release in soils. These f actors include pH, iron (Fe) and aluminum (AI) content, equilibration time, complementary ions, and background electrolyte. Preliminary studies were c onducted to determine appropriate experimental conditions for the study of Mo retention and release in two Florida soils. Traditional batch-type Mo is otherms were determined and the data were fit to common sorption mathematic al models on native and biosolids-incubated soils. Native soil Mo sorption is strongly related to soil pH; sorption is maximized at soil pH values <4 to 5 and is strongly hysteretic. Complementary ions (sulfate and phosphate) decrease Mo retention in the native soil. The adsorptive capacity of nativ e Millhopper (loamy, siliceous, hyperthermic Grossarenic Paleudults) soil i s <approximate to> 5 times greater than that of native Immokalee (sandy, si liceous, hyperthermic Aeric Alaquods) soil, consistent with their respectiv e native oxalate-extractable Fe and Al concentrations. Results from an incu bation study of biosolids-amended soils suggested increased Mo sorption on both soils due to addition of biosolids.