Heavy Metals in Sediments of Erhai Lake: Spatial-Temporal Distributions, Risk Assessment and Source Apportionment

Spatial-temporal distribution patterns, contamination assessment and source apportionment of Cd, As, Pb, Cu, Zn, and Cr in sediments of Erhai Lake, a large plateau lake in southwest China, were investigated. The results indicated that elevated concentrations of Cr, As, Cu, and Zn were primarily distributed in the eastern and central regions of Erhai Lake, whereas Cd and Pb were mainly concentrated in the west-central region. Cd exhibited the most severe pollution, with 15.4% of samples reaching extremely high single factor pollution index levels, followed by As, for which 65.8% of samples showed high contamination. Cu and Cr presented moderate pollution levels. In contrast, the geoaccumulation index indicated that 70.0% of Zn and 84.6% of Pb samples were unpolluted. Tourism, agricultural activities, and industrial activities contributed 29.90%, 15.32%, and 54.78% respectively by positive matrix factorization model. Specifically, Cu, Zn, As, and Cr originated predominantly from industrial activities, Cd showed strong associations with agricultural practices, and Pb was mainly ascribed to traffic-related pollution. Industrial sources contributed the most to ecological risk (62.50%). The temporal trend derived from the sediment cores revealed a surge in pollution levels during the early 21st century, which may be related to rapid economic growth and non-ferrous metal production. Overall, the results provide a valuable baseline for environmental monitoring and management in Erhai Lake.