Spatial and seasonal variation of potential toxic elements in Adocia pigmentifera, seawater and sediment from Rameswaram, southeast coast of India

Abstract

The concentrations of potential toxic elements (PTEs) such as cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn) were measured in five different stations of Rameswaram (RM) coast, Gulf of Mannar (GoM), India, in coastal waters in sediments and tissues of Adocia pigmentifera. Concentration of PTEs (Cd, Cu, Pb and Zn) was found to be highest in sediments followed by A. pigmentifera and seawater samples collected from the different stations of RM coast. The pattern of accumulation of PTEs in the three sample types is of the following order Zn < Pb < Cu < Cd. The seasonal variation of these PTEs also followed the same pattern. One-way analysis of variance (ANOVA) with Tukey’s HSD post hoc test has revealed significant differences among stations S1–S4 when compared with the station S5 which is considered as the reference site. Correlation coefficient study showed no significant correlation in the concentration of PTEs in A. pigmentifera, seawater and sediment samples. The concentration of all the PTEs in different sample types has exceeded the FAO/WHO/sediment background values, except for the concentration of Zn in A. pigmentifera and sediment sample, which did not exceed the limits. The contamination factor (CF) and geoaccumulation index (I geo) values indicated significant contamination of PTEs in the sediments from different stations of RM coast, India. Variations found between the sample types during the studies could be due to changes in levels of pollution discharge over time, availability of PTEs for adsorption as well as variations in the sampling season. Increasing urban sprawl and release of effluents both from domestic and industrial sources are the main sources of pollution at RM coast and are the prime reasons for the loss of existing diverse ecosystem.