JODHPUR, Nov. 22 -- Sambhar Lake, the country's largest inland saline lake located in Rajasthan, is increasingly coming under threat due to heavy metal contamination in its sediments, a geological study has revealed. Considering the presence of heavy metals, experts have warned that this could pose a potential ecological risk. The research conducted by five geologists from the Geological Survey of India (GSI) - Northeastern Region, Central Headquarters, RSAS Division, Bengaluru, and Western Region, Jaipur, titled, "Ecological risk mapping and heavy metal assessment in Sambhar Lake sediments", published this week in the journal Discover Geoscience, reports that the study examined the spatial distribution, contamination levels, and ecological risk of lead, nickel, chromium, copper, zinc, and cobalt in the surface sediments of Sambhar Lake, while identifying their potential sources. The geologists collected twenty-five sediment samples and analysed them using X-ray fluorescence spectrometry. Contamination was assessed using the contamination factor, enrichment factor, and geo-accumulation index, while overall pollution levels and ecological risks were evaluated through the pollution load index and potential ecological risk index. The study noted: "...Chromium was present in the highest amount, followed by zinc, nickel, copper, and lead. Cobalt had the lowest concentration, with chromium and nickel showing up as the most common contaminants. When compared to international sediment quality criteria, it is observed that copper, lead, and zinc are still below ecological threshold levels that could harm the environment. However, chromium often goes above levels that could have an effect, which could be bad for benthic creatures and the lake ecology." The study further explained that contamination indices generally categorize the sediments as uncontaminated to moderately contaminated, with localized enrichment of lead and chromium, largely along the lake periphery. Integrated indices show a small amount of pollution and a low overall ecological risk, although chromium and nickel add significantly to the risk profile. Multivariate analysis elucidates a dual contribution of sources: geogenic enrichment from Aravalli lithologies (notably chromium and nickel) and anthropogenic inputs from home sewage, agricultural run-off, and localised waste disposal. "The results show that the sediments in Sambhar Lake are mostly safe for every metal, but exhibit priority ecological concerns for chromium. To mitigate the contamination level in the study area, better sewage systems, well-planned farming, and public awareness are required," geologists suggested....