Pollution assessment and source analysis of heavy metals and nutrients in sediments of Liujiaxia reservoir, upper Yellow River, China

In August 2025, researchers collected 21 sediment samples from the Liujiaxia Reservoir in the upper Yellow River, China, to assess pollution characteristics, ecological risks, and sources of nutrients and heavy metals. Using sediment quality guidelines, a geo-accumulation index, and a potential ecological risk index, they evaluated pollution levels while employing Pearson correlation analysis, principal component analysis, and the APCS-MLR model for source apportionment.

The average concentrations of total nitrogen and total phosphorus were 566.19 mg/kg and 599.71 mg/kg, respectively. Heavy metal concentrations followed the order: zinc (78.71), chromium (49.05), nickel (29.67), copper (26.24), lead (24.52), arsenic (11.43), cadmium (0.11), and mercury (0.05). Nutrients and most heavy metals were mainly concentrated in tributary estuaries and deep-water zones.

Significant positive correlations were found between copper, nickel, zinc, chromium, and arsenic, indicating similar migration behaviors and common sources. However, nitrogen and phosphorus showed weak correlations with heavy metals, suggesting distinct enrichment pathways.

Overall, nutrient pollution was mild, and heavy metals posed a low ecological risk, although localized mercury enrichment and elevated nickel concentrations were observed at several sites. Principal component analysis revealed two main components explaining 70.36% of the total variance. The APCS-MLR model identified mixed natural and agricultural sources, industrial and traffic-related sources, and unidentified sources as contributing 43.8%, 30.5%, and 25.7% of heavy metal inputs, respectively.

The study concluded that sediment pollution in the Liujiaxia Reservoir remained relatively low, primarily influenced by natural weathering and agricultural non-point source inputs.