Distribution of different inorganic forms of arsenic in selected arsenic affected soils of the Bengal Delta Basin

Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur-741 252,

Nadia, India

E-mail : sarojsanyal@hotmail.com sarojsanyal@yahoo.co.in

Manuscript received 16 April 2004, revised 1 November 2004, accepted 19 January 2005

Inorganic soil arsenic (As) fractions from three representative arsenic affected surface soils of West Bengal, collected from Alllhikanagar, Chakla, lajpur (Block-Deganga, District·North 24-Parganas) as well as the control site at Gayespur (Biock-Chakdah, District-Nadia), were fractionated into different soil arsenic pools by following the sequential extraction methodology. These soils were also subjected to extraction of As by using several individual extracts In order to adjudge their efficacy in extracting soil arsenic fractions. The findings suggested that the Inorganic fractions of soil arsenic were In the order of Ws-As < Al-AS < Ca-As < Fe-As. The F contributed 44.7% to 74.7% towards arsenic sequential sum. Soils of lajpur had the highest sum of As fractions followed by those from Ambikanagar and Chakla. As regards the individual extractants used, the efficacy of the latter in extracting soil arsenic fell in the order, (NH₄)₂CO₃ ≈ CH₃COONH₄ < Na2CO₃ < NaHO₃ < NaOH ≈ NH₄F < HCI + H₂SO₄ < KH₂PO₄ < HCI < H₂SO₄. Among these extractants used, 0.5 N H₂SO₄ (pH 0.9) proved superior to others in releasing acidic and alkaline cation-bound arsenic in soils,  the 0.1 N NaOH (pH 13.0) also showed promise in releasing arsenic bound by the sesquioxides of the given agreement with the findings from the sequential extraction scheme followed In these soils. A careful perusal or these results suggested that Iron components played dominant role in facilitating accumulation of arsenic in these soils.