A source-oriented precise risk assessment of trace metal(loid)s in sediments of the Yangtze River Basin

Trace metal(loid)s (TMs) in river sediments pose significant threats to aquatic ecosystems and human health, with risk sources exhibiting substantial spatial heterogeneity across large basins. Precise identification of priority TMs for control and high-risk regions is critical for effective basin-scale management. This study integrated Positive Matrix Factorization (PMF) source apportionment with publicly available data (2000-2020) to assess source-specific ecological and human health risks in the Yangtze River sub-basins. The results demonstrated that Cd accumulation exceeded regional background levels by an average factor of 19.62 across all sub-basins, with anthropogenic activities (industrial, agricultural, and mining) contributing over 60 % of total TMs, especially exceeding 80 % in Dongtinghu (DTH) and Poyanghu (PYH). Ecological risk assessments revealed that 24.8 % of the basin exhibited moderate-to-high risk, with industrial sources alone accounting for 38.1 %. However, human health risks remained below safety thresholds (<1 % for both carcinogenic and non-carcinogenic risks). Markedly, agricultural-derived As dominated non-carcinogenic risk basin-wide, while industrial and natural sources, along with the elements Cr and As, respectively drove carcinogenic risk in most sub-basins. The DTH sub-basin, which exhibited the highest combined risks, required particularly stringent exposure controls (≤47 days/year for non-carcinogenic and ≤122 days/year for carcinogenic risks in children). This study refines the source-oriented assessment results and establishes specific exposure parameter thresholds. The result provides a scientific basis for preventive measures and precision management of heavy metal pollution in the Yangtze River Basin.