Factors affecting molybdenum sorption in soils: Potential biosolids effects

Many factors impact molybdenum (Mo) retention and release in soils. These factors include pH, iron (Fe) and aluminum (AI) content, equilibration time, complementary ions, and background electrolyte. Preliminary studies were conducted to determine appropriate experimental conditions for the study of Mo retention and release in two Florida soils. Traditional batch-type Mo isotherms were determined and the data were fit to common sorption mathematical 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 native Millhopper (loamy, siliceous, hyperthermic Grossarenic Paleudults) soil is <approximate to> 5 times greater than that of native Immokalee (sandy, siliceous, hyperthermic Aeric Alaquods) soil, consistent with their respective native oxalate-extractable Fe and Al concentrations. Results from an incubation study of biosolids-amended soils suggested increased Mo sorption on both soils due to addition of biosolids.