Solubility relationships of arsenic in calcareous soils and its uptake by corn

Summary The concentrations of total, water-extractable and DTPA extractable As were determined in 19 calcareous soils. The activity of HAsO₄^2– was calculated in the experimental soils and superimposed on the thermodynamic solubility isotherms of As minerals. It was observed that all the soils were undersaturated with respect to Ca₃(AsO₄)₂ and Mn₃(AsO₄)₂ (the most insoluble As minerals in the calcareous soils). The activity of Ca²⁺ in these soils was found to be in equilibrium with CaCO₃.Corn was grown in the experimental soils for 25 days. The corn plants were harvested, dried at 60°C, ground and analyzed for the concentrations of As. The concentrations of As in the plants were significantly correlated (P<0.05) to the water extractable As but not to the total and DTPA extractable concentrations of As in the soils. Sodium bicarbonate extractable P was significantly correlated (P<0.05) to both As in the corn and the water soluble As in the soils.