Spatial distribution of heavy metals contamination in sediments of alpine lakes and potential risk indices, Northern Pakistan

The current study worked on heavy metals concentrations in sediments of the alpine lakes in Gilgit-Baltistan, Northern Pakistan. Sediments samples (n = 41) from alpine lakes: Sadpara Lake, Rama Lake, Upper Kachura Lake, and Shausar Lake were collected. Sediments samples were digested according to standard protocol and analysed by atomic absorption spectrometry. Among heavy metals, Mn exhibited the highest mean concentration (333 mg/kg) in the sediments of alpine lakes, while Cd showed the lowest (1.48 mg/kg). The Ni, Cu, Cr, Mn, and Zn showed the highest mean concentrations in Sadpara Lake compared to other lakes. Sediments heavy metals concentrations were used for the calculation of pollution factors of alpine lakes, such as contamination factor (CF), pollution loads index (PLI), and ecological risk assessment (ERA). Among alpine lakes, the Sadpara Lake showed the highest PLI and CF values for most of the heavy metals. However, the highest mean (74.2 and 104) values of ERA and risk index (RI) were noted in the Rama Lake and exhibited a low-level risk to the alpine lake's system. Statistical analyses showed that weathering of bedrock and rich mineralised zone in the vicinity were dominating contributors of heavy metals contaminations.