This study was undertaken to evaluate the degree of heavy metal contamination in the lacustrine sediments and the corresponding environmental deterioration in a tropical, urban, coastal lake (Akkulam–Veli), located in Kerala, India. The study of the spatiotemporal variation of heavy metals in lake sediments is of great importance because heavy metals can result in toxic effects on aquatic biota through bioaccumulation. It also proves that extent of existing metal concentrations in sediments of river Cauvery in Karnataka not exceeded the toxic limit, and there is no peril to the aquatic life. This study concludes that insignificant geo-accumulation with metals except Cd (moderate contamination), Pb and Zn (slight contamination) principally in downstream stretch may perhaps deteriorate the sediment quality due to intensification anthropogenic influences. The statistical analysis of inter-metallic relationship revealed the high degree of correlation among the metals indicated their identical behaviour during transport. Negative total geo-accumulation indices (Itot) revealed that mean concentration of heavy metals in the river bed sediment are lower than their respective shale values. The geo-accumulation class (Igeo class) was in the sequence as follows: Cd>Zn>Pb>Cr>Cu>Co>Ni>Fe>Mn. The sediment geo-accumulation index (Igeo) showed maximum value of Cd (2.69) and least value of Mn (−1.44). Multivariate statistical techniques such as principal component analysis and cluster analysis (CA) were employed to better comprehend the controlling factors of sediment quality and spatial homogeneity among the stations. Analysis was carried out using flame furnace atomic absorption spectrophotometer, and results are expressed in micrograms per gram. Digestion of the samples was done by microwave-assisted digestion technique. Sampling was done for the period of 3 years (2007 to 2009). Twenty-five sampling points were selected based on geographical proximity of agricultural fields and industrial discharges river-tributary confluence points settlements located along the river bank ritual and recreational activities. Results were compared with sediment quality guidelines from various derived criteria. In this study, heavy metals such as Fe, Zn, Ni, Mn, Pb, Cu, Co, Cd and Cr were analysed in sediments. The purpose of this research work was to appraise extent of heavy metals in sediment and the degree to which its quality tainted seasonally and spatially in river Cauvery.
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