Potentially Toxic Elements: Distribution, Ecological Risk Assessment and Sources Identification in a Himalayan Lake in India

Abstract

Most of the inland open-waters, especially lakes, have been the victim of enhanced man-induced perturbations and are in a critical phase of ecological transition. Lakes function as long-term sinks for many pollutants including Potentially Toxic Elements (PTE), so the problems would further be accentuated due to environmental degradation and impending climate change scenario. Hence, a study was designed to evaluate the distribution of PTEs in water, sediments and fish (Pethia conchonius and Cyprinus carpio) of Sumendu (Mirik) Lake situated in the Eastern Himalayan part of India. It plays a significant role in providing means of livelihood to many sectors. Thirty-three sediment and water specimens were acquired from 11 sampling points to characterise the PTEs (Fe, Mn, Zn, Cu, Cr, Co, Cd, Ni, Pb, and As) concentrations levels using ICP-MS. Spatial distributional trends and pollution quality indexes were assessed for sediment samples. The degree of PTE exposure in the water and fishes were found to be within acceptable limits. The geostatistical prediction map showed that the concentration range of As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in sampling points were 2.61–10.1 µg g⁻¹, 0.02–0.48 µg g⁻¹, 4.85–17.5 µg g⁻¹, 32.2–84.7 µg g⁻¹, 24.2–47.1 µg g⁻¹, 13,007–61029 µg g⁻¹, 128.3–629.9 µg g⁻¹, 18.9–49.8 µg g⁻¹, 3.80–20.8 µg g⁻¹, 95.0–282.4 µg g⁻¹, respectively. Moreover, the sediment samples were found to be low to moderately polluted according to several pollution assessment indices viz. Degree of Contamination, Contamination Factor, Ecological Risk Index, etc. The findings of this research will aid in understanding potential contamination sources and significant pollution hotspots that could be utilised to develop contamination control strategies and targeted management tactics for Himalayan fresh water lakes.