Fig. 1. Selenium sorption as a function of pH expressed as the percentage of Se sorbed relative to Se applied. Applied concentrations were 6.64 µmol L^–1 for Se(IV) and 5.22 µmol L^–1 for Se(VI), which is mid-range of the concentrations used to construct the multiconcentration isotherms. The ratio of soil mass to solution volume were 1:50 and 1:20 for Se(IV) and Se(VI), respectively.