Co-deposition and distribution of arsenic and oxidizable organic carbon in the sedimentary basin of West Bengal, India

Background: The study investigated the extent of soil arsenic (As) contamination in agricultural plots in Bengal Delta through contaminated groundwater irrigation. Edaphic levels of As and oxidizable organic carbon (OOC) were tested along a depth gradient (0 to 160 ft) in agricultural plots. Methods: Soil samples were collected from surface up to 160 feet depth at every 5 feet. By boreholes drilling and soil arsenic was estimated in ICP-MS. The analysis for estimation of soil OOC was performed. Statistical analyses were performed by one-way ANOVA to determine significant differences between groups at P<0.05. Results: Concentration of As in soil was observed to be highest in surface soil, then decreased with increasing depth till about 40 ft, after which the concentration remained constant. Similar trends were noted for OOC. OOC showed significant (P < 0.05) positive correlations with the As levels. Conclusion: Natural organic matter may enhance the release of As from soils and sediments into the soil solution, and thus can help in As leaching into the groundwater. Detailed investigation of the soil profile and the extent of bioaccumulation in the edible crops are urgently needed in those arsenic-contaminated areas.