Distribution, contamination, and environmental risk assessment of potentially bioavailable trace elements in the complexly impacted catchment basin of Lake Sevan (Armenia)

Lake Sevan (Armenia), the largest high-altitude freshwater lake in Eurasia, has an ecologically important catchment. However, data on trace elements (TEs) in the sediments and waters of rivers feeding Lake Sevan remain limited. To address this, sediment and water samples were collected across the basin to determine water-soluble TEs in sediments and dissolved TEs in river waters and to assess their spatial distribution, geochemical patterns, relative enrichment, and potential environmental and human health implications. Relative enrichment, pollution, and potential human health risks were evaluated using contamination factor (CF), pollution load index (PLI), Nemerow pollution index (NPI), and hazard index (HI). Results showed substantial spatial variability in TE concentrations, consistent with the combined influence of geological conditions and anthropogenic pressures. Cluster analysis separated upper and lower river reaches into geochemical groups. CF indicated high relative enrichment in the water-soluble sediment fraction by As, Mn, Mo, Ni, Pb, Sb, and V at specific locations, with the upper Masrik River system, downstream of the Sotk gold mine, showing the most pronounced relative enrichment. This pattern is consistent with the mineralogical characteristics of the Sotk deposit and may reflect mining-related inputs. PLI revealed pronounced spatial variability in the combined relative enrichment of water-soluble TEs, with the highest enrichment in the upper Masrik River system and elevated values at sites in the lower reaches of the Dzknaget, Karchaghbyur, and Gavaraget rivers and the Masrik River system. In waters, most TE concentrations were within local standards, but NPI indicated heavy pollution in the Masrik River system and the lower reaches of the Gavaraget and Vardenis rivers. Health risk assessment indicated potential non-carcinogenic risks under the hypothetical drinking-water exposure scenario in the upper Masrik River system and occasionally in the lower Masrik River system, primarily associated with elevated dissolved As and Sb levels. Principal component analysis further supported spatial differentiation in TE composition and identified distinct elemental associations among sampling sites. Overall, the Masrik–Sotk system emerged as the most prominent area of multi-element enrichment among the investigated sites, while localized enrichment was also observed in several other downstream reaches.