Pollution loads and ecological risk assessment of metals and a metalloid in the surface sediment of keenjhar lake, pakistan

Abstract

This study aims to analyze the concentrations of heavy metals and a metalloid in the surface sediments of Keenjhar Lake, Sindh, Pakistan that pose a risk to the lake ecosystem. The concentrations and ecological risks associated with eight metals and a metalloid (As, Pb, Cd, Cu, Mn, Fe, Ni, Hg, and Cr) from surface sediments of the lake, was evaluated at 10 sampling locations. The overall 95th percentile concentrations of trace elements were observed as As (29.1), Pb (7.6), Cd (0.68), Cu (9.3), Mn (56.43), Fe (352.3), Ni (10.36), and Cr (29.61) mg/kg. Metal wise as well as aggregated levels of contamination were studied. It was observed that all metals except Hg were detected in the lake sediment. Based on the geo-accumulation index and enrichment factor, Cr, Cu, Mn, Ni, and Pb showed low pollution levels, while As, Cd, and Fe showed a high degree of contamination. Based on the 95th percentile, the average values of EF for As, Cd and Fe were observed as 274%, 300% and 907% respectively. Pollution Load Index reflected metals and metalloid contamination near the warning threshold, with an average value of 0.825. The Nemerow integrated pollution index (range 6.79-7.59, i.e., >3) and degree of contamination (range 12-24) suggested strong pollution levels. According to the findings of the ecological risk index, Cd showed high ecological risk (between 160-320) at all sampling sites, and potential ecological risk index was at moderate risk level (between 150-300) at all locations. Multivariate analysis of the metals and a metalloid classified as As, Cd, and Fe in one group with the remaining metals in another group show that metals of each group originate from the same source.