Bioavailability and toxicity of arsenic to earthworms in three soils

All the three different soils were spiked using aqueous solution of As(V) (Na2HAsO4.7H2O, Sigma) or As(III) (NaAsO2) to obtain final concentrations in soil of 0-1000 mg kg−1 dry soil. The soil samples were thoroughly mixed to obtain uniform distribution of As in soil. The spiked soils (150 g) were placed in plastic jars (500 ml). The soils were maintained at 75% of water holding capacity by adding appropriate amounts of deionized water. All experiments were conducted with two replicates per exposure concentration. Soils without As served as controls.