Assessment of metals pollution and subsequent ecological risk in water, sediments and vegetation from a shallow lake: a case study from Ranipet industrial town, Tamil Nadu, India

The present study investigated the distribution, sources, bioavailable fractions, and ecological risks of nine metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Pb, and Zn) in water, sediment, and vegetation samples collected from a shallow lake within the industrial town of Ranipet, India. The lake water samples exceeded the concentrations of Al, Cd, Cr, Cu, Fe, Mn, and Pb beyond BIS (Bureau of Indian Standards) limits for drinking water with Cr to be highest as 6.73 mg/L. The Geo-accumulation index for lake bed sediment samples were in the order of Cr>Cu>Co>Mn>Zn>Pb. The bioavailability of the metals in sediment samples determined through Sequential Extraction Procedure (SEP) showed Cr>Co>Zn>Cu>Pb>Mn>Fe>Al. The sediment samples collected from the root zone of different plant species (Cynodon dactylon, Sida acuta, and Eclipta prostrata) exhibited varied bioavailable fractions than lake bed sediments, which indicated the influence of plants in mobilising and fixing the metals. The plant samples had metals concentration in the order of Root>Stem>Leaves and showed the possibility of phytoremediation. Principle Component Analysis (PCA) and Pearson Correlation Matrix (PCM) in the lake bed sediment samples identified the clustering of Al and Fe which indicated probable lithological origin. The lone clustering of Cr from Co, Mn, and Cu indicated separate anthropogenic sources. Further Al, Fe, and Mn showed strong correlations with TOC (Total Organic Carbon) substantiate their distribution under influence of TOC. The study indicated elevated metals pollution is water, sediment, and plants samples from lake area which require immediate attention from all the stakeholders. The assessment of pollution in small and shallow lakes amidst industrial belts need to be prioritised as they often become victims of industrial encroachment and cease to exist in long run.