Arsenic fractionation and its remediation in agricultural soils of Bangladesh

Abstract

A laboratory batch experiment was conducted to find out the various fractions of arsenic in two contaminated calcareous high pH soils from Bagerhat and Kashiani and uncontaminated low pH soil from Madhupur of Bangladesh with an aim to understand arsenic dynamics in soils required to develop remedial measures against arsenic contamination. Study was conducted on soil samples by spiking with different combinations and sequence of anions – arsenic (As), phosphorous (P) and sulphur (S). Phosphate and sulphate were chosen as desorptive solutions because they are common soil nutrients. Seven different combinations of the anion application sequence at two different concentrations resulted in fourteen different treatments applied to soil samples which were subjected to fractionation study following the 5-step sequential extraction procedure (SEP) developed by Wenzel et al. (2001). Study on “Resident time effect” was also performed for by conducting the SEP at 0 day, 7 days and 30 days of incubation after spiking the samples. SEP was also carried out on the untreated samples. The total concentration of Arsenic in Bagerhat, Kashiyani and Modhupur soils were found 22.0, 88.0 and 3.68 mg kg -1 , respectively. Very good correlation between total arsenic content and organic matter, phosphorus, calcium and carbonate content of the samples. Moderate correlation was obtained between arsenic content and CEC, pH and iron.