Geochemistry of surface sediments of a tropical brackish water lake in South Asia

This article presents the result of the geochemical analysis of sediment from Pulicat lake, India. The analysis consists of textural composition, CaCO₃, organic carbon, total phosphorus, metals such as Cr, Ni, Cu, Pb, Zn, Cd, Fe and Mn of the sediments collected. Multivariate analysis is performed on the dataset and the interpretations are used as pointers to the origin of the composition of sediment components. Analysis shows a strong intermetal relationship, with lesser correlation with sand or mud which indicates that the metals have a common origin and they were already agglomerated before reaching the lake. Contamination Factor and Geoaccumulation Index demonstrated that the sediments were moderately contaminated with Cd. The Pollution Load Index for the Cd, Cr, Cu and Pb were greater than 1, whereby a Pollution Load Index greater than 1 indicates that the system under study is undergoing progressive deterioration representing Cd>Cu>Pb>Cr>Ni>Mn>Zn. Hierarchy of EF for metals in sediments is Cd > Cu > Pb > Cr > Ni > Mn > Zn with average of 3.6 > 2.1 > 1.8 > 1.4 > 1.0 > 0.8 > 0.7, respectively. Cd concentration varies from a minimum of 0.01–1.5 mg kg⁻¹ with a mean of 0.77 mg kg⁻¹. Cu concentration ranges from 25 mg kg⁻¹ and maximum of 81 mg kg⁻¹ with a mean of 50 mg kg⁻¹. Most of the metals are concentrated in the stations near the eastern part, which lie parallel to the sea and these regions act as hot spots for metal accumulation.