This study investigated the distribution and source of heavy metals and dispersed elements in the high-salinity brine of Qarhan Salt Lake. The brine with an average total dissolved solid content of 332.22 g/L, dominated by Cl⁻ (216.41 g/L) and Mg²⁺ (44.76 g/L), indicated strong evaporation and dolomite dissolution. As (6.57 ± 3.59 μg/L) and Hg (0.48 ± 0.14 μg/L) showed uniform distribution while Li (69.66 mg/L), B₂O₃ (317.80 mg/L), and Zn (5.69 mg/L) were highly enriched, highlighting the resource potential and geochemical complexity. Correlation analysis revealed that water–rock interaction played a key role in element differentiation, with Sr and Ca²⁺/Cl⁻ showing strong positive correlations (r = 0.693/0.768), reflecting isomorphic substitution and dissolution. Meanwhile, Na⁺ and Mg²⁺/Ca²⁺ showed negative correlations (r = −0.732/−0.889), suggesting cation exchange and gypsum precipitation. The self-organizing map yielded four clusters of elements and positive matrix factorization model identified four sources; the elements in the Salt Lake brine mainly came from the river water supply, weathering and leaching of minerals, and dissolution of salt-bearing layers and were locally influenced by human activities. The research provided valuable insights for future sustainable development and the environmental protection of the region.

The fragile ecological environment of the Qinghai–Tibet Plateau (QTP) is significantly affected by human activities. This study employed a self-organizing map (SOM) for cluster analysis and positive matrix factorization (PMF) to trace the source of potentially toxic elements (PTEs) in the surface water of rivers. The results revealed that the average concentration of PTEs in the rivers was generally low. However, at some sampling points, especially in areas near the Qarhan Salt Lake, the content of Cu, Hg, and Ni were high. The water quality index (WQI), contamination factor (CF), and modified contamination index (mCd) identified good water quality, while potential Ni in the Quanji and Golmud River basins were the primary contaminants of concern. The potential ecological risk index (PERI) showed a low ecological risk. The SOM yielded four clusters of water PTEs, including Hg, Cu-Ni, Pb-Cd-Zn, and As. PMF model further revealed PTE sources, with industrial sources (39.73%) as the primary anthropogenic factor, followed by natural weathering (33.44%), vehicle emissions (21.52%), and atmospheric deposition (5.31%). This study laid the foundation for the ecological monitoring of rivers on the QTP and provided a reference for balancing industrial development and ecological protection in Qarhan Salt Lake areas.

The Cascade Reservoir System (CRS) in the upper Yellow River delivers integrated benefits (flood control, water supply, hydro-power generation, and ecological regulation), but it also alters the natural runoff regime and exerts non-negligible impacts on the regional eco-environment. However, the long-term trajectory of reservoir-cascade effects on land use/land cover (LULC) in alpine basins has not yet been systematically quantified. Here, we focused on the Hualong-Xunhua reach and delineated two impact domains—the Reservoir Influence Zone (RIZ, enclosed by the first-order mountain ridge lines closest to the river channel representing direct hydrological impacts) and the Local Microclimate Influence Zone (LMIZ, spanning from the first-order ridges to the outer watershed boundary representing indirect climatic impacts)—to investigate the spatiotemporal dynamics of LULC associated with reservoir development. Results show that, from 1985 to 2023 in the CRS area, cropland and shrub-land decreased by 89.56 km² (−16.09%) and 9.41% (−9.41%), respectively, whereas forest and grassland increased by 79.92 km² (+14.36%) and 7.74% (+7.74%). Within the RIZ, cropland declined by 29.49 km² (−20.14%), while water bodies increased markedly by 32.19 km² (+22%); forest cover also expanded by 9.09 km² (+6.21%). In the LMIZ, forest and grassland exhibited pronounced increases of 70.83 km² (+17.27%) and 39.37 km² (+9.60%), respectively. Correlation analysis indicates that GDP and air temperature are strongly and positively correlated with forest, water bodies, and impervious surfaces (Pearson’s r > 0.9), whereas cropland shows significant negative correlations with GDP, forest, and grassland (Pearson’s r < −0.8). Overall, the distinct spatiotemporal contrasts between the RIZ and LMIZ, coupled with the temporal alignment of cropland-to-forest transitions post-2000, suggest that reservoir-cascade construction and the Grain-for-Green Project are associated with these major LULC transitions, serving as contributing factors, while temperature rise and GDP growth represented the background environmental and socioeconomic context. These findings provide data support and a conceptual basis for long-term monitoring and assessment of eco-environmental responses to reservoir cascade development, and offer scientific evidence particularly relevant to reservoir planning and management in high-altitude cold regions.