Solubility relationships of arsenic in calcareous soils and its uptake by corn
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The concentrations of total, water-extractable and DTPA extractable As were determined in 19 calcareous soils. The activity of HAsO 4 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.
Key wordsArsenic As minerals in soils Calcium solubility Plant uptake Water extractable
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