Transport of aqueous arsenic in selected arsenic affected soils of West Bengal: A miscible displacement study

摘要

A laboratory transport study of aqueous arsenic under constant pressure head in four surface soils,collected from the paddy fields at four different arsenic-affected sites of the Deganga block of North 24-Parganas district of West Bengal,was conducted with the help of double-chambered vertical column made of Borosil glass.The experimental data led to the Darcy's saturated hydraulic conductivity of the soils and accumulation or relative hold-up of arsenic in these soils as revealed by the corresponding breakthrough curves.The sigmoid shape of these breakthrough curves for the given passage of aqueous arsenic solutions through the present soils,there by suggesting hydrodynamic dispersion,was noted,with a concomitant shift of the curves to the left of the corresponding inflextion points (at P_v = 1.0).Based on this,substantial arsenic retention by the given soils was inferred.In this regard,the arsenic retention through its interactions with the soil organic matter and the clay fractions was also emphasized.Moreover,an attempt lias been made in the present study to relate the arsenic retention by the given soils to the corresponding relevant physico-chemical properties.The findings from the laboratory experiment were found to be satisfactorily correlated with the arsenic build-up in the different parts of summer (boro) paddy cultivated in the given affected soils.The latter may be taken to elucidate the effect of such irrigation on crops grown in the arsenic contaminated soils using the contaminated groundwater as the irrigation source.