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The Himalayan lakes are facing an acute problem of survival due to increased concentration of toxic elements in water and sediments. In the present study, the heavy metal contamination history of Renuka Lake during the calendar year (ca) 1839–2003 AD has been performed using 137Cs and 210Pb radionuclide-dated core sediment sample and Inductively-Coupled Plasma Mass Spectrometry (ICP-MS). The concentration of heavy metals (Mn, Cr, Cu, Zn, Ni, Pb and Co) during the said time period is found to have significant variations and suggested a contribution of both natural and anthropogenic factors like surrounding rocks, burning of fossil fuels, sewage and agro-chemicals. The highest concentration of Mn is observed during ca 1847, which is 4–5 times more than ca 2003. The Cr is found to be highest during ca 1962; whereas Cu, Zn, Ni and Pb are observed highest during 1883. Similarly, Co is determined highest during ca 1939. The contamination factor (Cf) indicated low to the considerable level of contamination, whereas the degree of contamination (Cd) revealed a low level of contamination in the lake. However, the geo-accumulation index (Igeo) marked the lake uncontaminated to moderately contaminated and on the other hand, the pollution load index (PLI) showed some signs of contamination in the Renuka Lake. The present study has been compared with other lakes and the background concentration of average shale, upper crust, crustal average and carbonate rocks. Although, keeping in view historical contamination, there is a need of stringent steps for the preservation of the Renuka Lake.

The lakes of the Himalaya are degrading due to increase in toxic heavy metal loading. This study reports the last 50-year heavy metal pollution loading in the Rewalsar Lake, Himachal Pradesh, India. Sediment cores were recovered to study the pollution loading in the lake sediments. The 137Cs and 210Pb isotope-based sedimentation rate suggest rapid sedimentation in the lake during the last ~50 years. The concentrations of Mn, Cu, Zn, Cd, Pb, Co, Ni, Cr metals in the lake sediments owe its contributions both to the natural and anthropogenic sources. Prior to ca 1990 AD, metal loading was dominated by the lithogenic input, whereas post ca 1990 AD the metal loading was controlled by the anthropogenic factors. The Pb concentration in the lake gradually increased during 1990–2004 and then decreased significantly till present. The higher concentration of Pb seems to be derived from the fossil fuel burning, while the Cr concentration in the lake indicates the use of fertilizer in the catchment area. The lowest concentrations of elements around ca 1990 AD seem to have occurred due to channelization of the lake feeding system.