Batch dissolution experiments were carried out on two different types of aquifer sediments collected from drill core samples of Fcontaminated alluvial aquifer of Birbhum district, West Bengal. One of the samples represents sand having quartz, k-feldsper, muscovite, biotite and Fe-Mg minerals and the other is silty-clay in nature having quartz, K-feldsper and zeolite minerals. Batch dissolution experiments showed that the maximum concentration of F was found in Na-rich solution at 500 hr of interaction time whereas in case of silty-clay sample the optimum concentration was found at 300 hr. However silty-clay samples release 6 times more F than sand sample. With respect to the contribution from other cations and anions Na and HCO3 play major role in mobilizing F. In case of sand sample weathering of muscovite/biotite is the principal mechanism of mobilizing F in comparison to the ionexchange mechanism in silty-clay samples. Apart from HCO3, Na/Ca ratio also plays a significant role in mobilizing F from sediment matrix. Experiment shows that in comparison to the deionized water, solution having Na/Ca>1 releases 25% and 7% more F from silty-clay and sand samples respectively.
