Organo-arsenic Complexation Studies Explaining the Reduction of Uptake of Arsenic in Wheat Grown with Contaminated Irrigation Water and Organic Amendments
2021
Kumar, Shyam Nandan | Miśra, Bipina Bihārī | Kumar, Sunil | Mandal, Jajati
Application of organics in soil can reduce uptake of arsenic (As) in food crops grown on soil spiked with As. However, the results may be different if the crop is grown with As-contaminated irrigation water. In this study, a modest initiative has been undertaken to assess the organo-arsenic equilibria using the fulvic and humic extracted from paddy husk (PH), vermicompost (VC), and soil. The fulvic and humic acids were found to be polyprotic in nature. Fulvic acid extracted from paddy husk have the highest mole ratio or combining ability of 1.88 ± 0.59 and stability constant (log K) of 8.96 ± 0.21. Based on the above findings, a greenhouse experiment with wheat crop was conducted using different concentrations of As in irrigation water (1, 2, 4, and 8 mg L⁻¹), irrigated 5 times throughout the crop growth period and 3 levels of amendments (No amendment, VC and PH @ 10 t ha⁻¹ each). Paddy husk and also vermicompost can be effectively used as an amendment to trim down the bioavailability of arsenic in the wheat grain provided the As content in irrigation water is < 2 mg L⁻¹. Risk assessment of As spiked soils was carried out and expressed in hazard quotient as per USEPA guideline. Solubility free ion activity model was also used to forecast the transfer of As from As spiked soil to wheat grain.
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