Impact of sedimentary arsenic through irrigated groundwater on soil, plant, crops and human continuum from Bengal delta: special reference to raw and cooked rice

Abstract

Existence of arsenic-rich (exceeds 2,000 mg/kg) iron pyrite in Bengal delta sediments is responsible for arsenic release in aquifer. Ingestion of contaminated drinking water is not the only elevated source of arsenic to the diet. Irrigation of agricultural fields with arsenic-contaminated groundwater has led to arsenic build-up in soil, with subsequent elevation of arsenic in crops grown on these soils. About 50.7 and 11.2 kg of arsenic are withdrawn per year from 23 and 18 shallow tubewells, used for agricultural irrigation in the studied two districts Murshidabad and Nadia, respectively and deposited on lands throughout the year. Considerable higher amounts of arsenic are accumulated in paddy plants. Mean arsenic concentration in food categories is 107 microg/kg. Arsenic concentrations are high in cooked food and skin of the vegetables. Arsenic concentration in cooked rice increases with water arsenic concentration. About 70.2% of arsenic is recovered by using the analytical speciation extraction method. Inorganic arsenic and DMA contribute 89.5% and 10.5% of the total content of arsenic in food, respectively. About 0.081% and 1.57% of arsenic are accumulated in rice grain from arsenic-deposited lands and contaminated soils. The daily dietary intake of inorganic arsenic (mug/kg body wt./day) by an adult from rice grain itself (2.32) is higher than the WHO recommended PTDI value of inorganic arsenic (2.1) and inorganic arsenic contributes 96.8% of the total dietary intakes of arsenic. Population exposed to arsenic toxicity has been identified.