Spatiotemporal characterization of dissolved trace elements in the Gandaki River, Central Himalaya Nepal

A comprehensive investigation was conducted on trace elements (TEs) in the glacier-fed Gandaki River Basin, Central Himalayas Nepal. A total of 93 water samples were collected from 31 locations in pre-monsoon, monsoon and post-monsoon seasons in 2016 to evaluate the concentrations of TEs. Multivariate statistical techniques such as analysis of variance, cluster analysis, principal component analysis, and correlation analysis were applied to investigate the spatiotemporal variations and identify the major sources of the TEs. The results classified most of the TEs into two groups. Group 1 including Cs, Li, Ni, Rb, Sc, Sr, Tl, U and V were from geogenic sources, while Group 2 including Cd, Co, Cr, Cu, Pb, Ti, Y and Zn were impacted by anthropogenic activities. Group 1 showed lower concentrations in the lower-middle and downstream segments with higher precipitation and the highest concentrations during pre-monsoon. In contrast, Group 2 demonstrated higher concentrations in the densely populated lower segments with more agriculture and industries, and the highest concentrations during the post-monsoon season. Comparing to the drinking water limits suggested that special attention should be paid to the elevated concentrations of Zn and As. The results of the study provide a basic guideline for future environmental protection in the Himalaya.