Heavy metal fractionation and mineralogy in sediments of Nainital lake, Kumaun Himalayas

The major objective of the present study has been to determine the mineralogy and chemical composition of sediments of Nainital lake, a major tourist destination situated in the Kumaun Himalayas. In the present study, we have determined the mineral content in the sediments of the lake and analysed the associations of toxic metals in various chemical fractions such as, metals which are easily released to water from sediments, and metals bound to carbonates, manganese oxides, iron oxides, organic matter and residual matter. Although detrital minerals quartz and feldspar are dominant, calcite, aragonite, illite and gypsum are also present in appreciable quantities. Quartz and illite are the dominant minerals in the coarse fractions of sediments, whereas calcite, aragonite and gypsum are mostly present in finer sediments. Among the various chemical fractions, most of the metal concentrations are associated with the residual fraction, whereas, organic matter fraction is a major sink for Mn, Zn and Cu. Hence, under conditions where organic matter gets oxidized, the metals may be released into the water column, thus resulting in high pollution levels in the lake waters.