Contamination and mobilization of arsenic in the soil and groundwater and its influence on the irrigated crops, Manipur Valley, India

The arsenic concentration in groundwater used for irrigating the rice crops varies from 10 to 475 ppb. The Disang shales, deposited under marine environment, appear to be the main source of arsenic contaminating the groundwater. The arsenic content in the rice roots vary from 32 to 52 ppm while the arsenic in the grains is far above the limit prescribed by WHO. Sequential extraction process results indicate that a large part of arsenic is present in the residual phases. High concentration of arsenic at root depth is present in crystalline Fe-oxides and is available for the rice plants. Sequential extraction experiment on soils indicate low arsenic content in organic matter compared to the above phases