A comprehensive study on distribution, migration, risk and source of heavy metals in lake, river and salt lake in the largest watershed of the Qaidam Basin.

Heavy metal contamination in high-altitude watersheds of the Qinghai-Tibet Plateau (QTP) has garnered increasing attention due to the region's ecological sensitivity. This study investigated the concentrations, migration, contamination levels, and sources of seven heavy metals (Cd, Cr, Cu, Pb, Zn, As, and Mn) in surface sediments collected from lake, river, and salt lake within the Golmud River basin. Multiple pollution indices, including enrichment factor (EF), geo-accumulation index (Igeo), and pollution load index were employed for contamination assessment, while positive matrix factorization (PMF) and self-organizing map (SOM) were integrated for quantitative source apportionment. Results revealed significant spatial heterogeneity across sedimentary systems and the migration with a concentration gradient. Overall, the pollution pattern demonstrates that with As, Cu, and Pb identified as primary contaminants. PMF analysis identified three sources: natural weathering (34.26%), industrial activities (39.19%), and transportation emissions (26.55%). SOM analysis further delineated three distinct clusters corresponding to anthropocentric impacted, mixed-source, and natural background areas. This study provides critical insights for watershed management and sustainable development of salt lake resources on the QTP.