Fractionation of inorganic Arsenic and determination of its safe limit in irrigation water in rice
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Date
2020
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Department of Soil Science and Agricultural Chemistry, BAU, Sabour
Abstract
A pot experiment was conducted with two soil types (alluvial and red) using ten levels (of contaminated irrigation water (0, 0.25, 0.5, 0.75, 1.0, 1.25, 1.50, 1.75, 2.0, 2.25 mg L-1), irrigated for 5 times using rice (Variety: Sushak Samrat) as a test crop to determine the safe limit for irrigation water contaminated with As. The increase in the level of contamination in the irrigation water significantly affected the yield attributing characters and yield in both the soils. The results reveal that the different fractions of arsenic, water soluble arsenic (F1), Aluminium bound arsenic (F2), amorphous iron bound arsenic (F3), crystalline iron bound arsenic (F4) and Calcium bound arsenic (F5)in terms of its profusion followed the order F4 > F2 > F5 > F3 > F1 and F4 > F3 > F2 > F5 > F1across all the doses of As for alluvial soil and red soil respectively. The safe limit of irrigation water in terms of risk assessment expressed as Hazard Quotient (HQ) was 0.75 mg L-1 and the solubility FIAM can effectively predict the As content in rice grain in both the soils. The Tobit Regression Model, which is a censored model served as an effective tool in predicting the safe limit of irrigation water based on the inherent soil As content. In alluvial soil the safe limit for As in irrigation water is from 1.20 to 0.10 mg L-1 and for red soil, the range is from 0.10 to 0.40 mg L-1 based on the available soil As and provided that the As content in rice grain is < 0.4 mg Kg-1. This can be used as an effective protocol for estimation of safe limits for irrigation water which will vary for diverse soils having varied physio-chemical properties acting as a sink and plays the role for water-soil-food transfer of the contaminant.