This paper is the result of geological survey engineering.

Objective Dongting Lake, the second largest freshwater lake in China, has experienced increased heavy metal accumulation due to surrounding mining activities and chemical metallurgy. Understanding the characteristics and sources of heavy metal pollution in Dongting Lake is crucial for effective prevention, control and remediation efforts.

Methods In August 2023, 37 surface sediment samples were collected from four main inflow rivers of Dongting Lake. Eight heavy metals and their physicochemical indicators were measured. The pollution characteristics were evaluated using sediment quality guidelines (SQG). The potential ecological risk index method was used to identify the ecological risk of sediments in the area. The sources and contribution rates of the heavy metals were analyzed using the Positive Matrix Factorization (PMF) model and correlation analysis. Redundancy analysis (RDA) was used to explore the morphological characteristics of heavy metals in sediments.

Results The ecological risk of heavy metals in the sediments of the Dongting Lake water system is relatively high, Cd contributed the most to ecological risk (75.1%), followed by Hg (17.2%).with the Xiangjiang and Zijiang river basins exhibiting higher heavy metal pollution risks. Based on the PMF model and regional characteristics, four potential sources of heavy metal pollution in the sediments were identified: agricultural sources (42.7%), atmospheric deposition sources (16.1%), natural sources (21.8%) and metal smelting sources (19.5%). The RDA results showed that the heavy metals in the sediments of the four drainage basins were mainly Fe−Mn combined.

Conclusion According to RDA and related analyses, it is indicated that the content of heavy metals such as Cd in the lake area sediments is mainly controlled by Fe and Mn oxides. In the next step of environmental remediation and pollution control, the oxide characteristics of iron and manganese can be utilized to effectively control and treat heavy metal pollution.