Impact of irrigation and organic matter amendments on arsenic accumulation in selected vegetables

The present study was set up to investigate the effect of irrigation with naturally arsenic (As)-contaminated water and addition of organic amendments on the As accumulation in frequently consumed vegetables in India (pumpkin, radish and cabbage). An arsenic-stricken village (Ghentugachi, Chakdah Block, Nadia, West Bengal, India; 23°02'N, 88°34'E, 9.75 m a.s.l.) was selected. Pot studies were conducted with the selected vegetables in contaminated soils collected from the selected village. Arsenic-contaminated water (spiked with varying concentrations of AsIII and AsV) was used to irrigate the pots. Use of irrigation water contaminated with arsenic (both AsIII and AsV) reduced the germination and inhibited photosynthetic pigmentation. AsIII contamination remained more harmful. The worst situation was encountered with AsIII contamination at 0.5 mg/L of irrigation water while AsV contamination below 0.2 mg/L of irrigation water remained safe. Field experiments with the selected vegetables were undertaken in the arsenic-stricken village where irrigation water (0.32 ± 0.12 mg/L) and soil (total As 18.15 ± 2.12 mg/kg) were contaminated with arsenic, to characterize the arsenic contamination of the vegetables, to assess the risk of dietary exposure and to study the effect of organic amendments on such contaminations. Vegetable roots accumulated more As than other parts and the accumulation increased with age. Pond (surface) water emerged as safer source for irrigation than shallow tube well water. Organic amendments reduced arsenic contamination significantly and vermicompost was the most efficient in this regard. All the vegetables showed risk (> 100% provisional tolerable weekly intake) of dietary exposure to arsenic.