ABSTRACT
Drinking of contaminated groundwater is a major route of arsenic exposure, but the problem is aggravated when the same water is used for irrigation purposes. Our study based in arsenic-affected district North 24 Parganas of West Bengal deciphers the impact of arsenic-contaminated groundwater (mean: 178.5 ± 105 µg/l; range: 75.5–295.5 µg/l) on paddy and its accumulation and distribution patterns in field soil and plant parts during various stages of pre-monsoonal cultivation (Boro). A decreasing trend of arsenic concentration was observed in plant parts during the reproductive stage compared to the vegetative stage and a reversal in ripening stage due to iron plaque formation. During the growth period, higher concentrations of iron in root soil at the reproductive phase confirmed the development of plaques on the root surface, which sequester arsenic and prevent its uptake. Monsoonal paddy farming too requires groundwater, due to scarcity of rain. So, accumulation and uptake pattern depend on groundwater, phase-wise movement of soil arsenic with its enrichment status and variation of rainfall. The synergistic effect of groundwater and rainwater makes a unique impact on arsenic distribution in plants, since rainwater dilutes arsenic available for translocation. This phenomenon produces least arsenic (318 µg/kg) containing grain (one-third of Boro) irrespective of cultivar variety and cultivation area. Higher accumulation of arsenic was observed in parboiled rice due to domestic-scale post-harvesting of paddy using arsenic-contaminated groundwater and additional risks were posed to populations through consumption of parboiled rice, especially used in cooked rice preparation and its derivatives. The entry or elimination (movement) of arsenic to/from grain and water during cooking is conspicuous. Lower arsenic in cooked rice was observed when rice grain is cooked with low/moderate arsenic-contaminated water (>3–50 µg/l) and arsenic movement from water to rice grain was inferred with increasing water arsenic (<70 µg/l). Selenium is inversely proportional to arsenic in cooked rice for both cases. Concurrently, a similar reduction percentage of arsenite, arsenate and total arsenic was seen in wet cooked rice when cooked with low-arsenic-containing water.
