Basin-specific criteria derivation and risk prioritization of heavy metals in the Yellow River

The Yellow River serves as a critical water source for northern China, yet basin‑wide information on heavy metal pollution, ecological and human health risks, and region‑specific regulatory thresholds remains limited. Here, nine heavy metals were analyzed in water and organisms across the Yellow River Basin (YRB) and an integrated risk assessment was conducted using newly derived basin‑specific water quality criteria (WQCs). Most metals exhibited elevated levels in the middle reaches, whereas As was enriched upstream. Industrial and transportation activities mainly contributed to Mn, Zn, Ni, Co, Pb, and Cd, whereas Cu, As, Cr, and partly Zn were linked to combined industrial and agricultural inputs. For the first time, YRB‑tailored WQCs of these metals were established by incorporating local species sensitivity and hydrochemical conditions via species sensitivity distribution and biotic ligand model approaches. Cr was identified as posing relatively high acute ecological risk, and both Cr and Cu presented significant chronic risks to aquatic organisms. As and Cr were highlighted as the major carcinogenic concerns for human health, with Cr exceeding internationally acceptable risk levels through drinking water. Bioaccumulation of these metals in aquatic organisms collected from Inner Mongolia section varied, and Cd and As posed the greatest non-carcinogenic and carcinogenic risks, particularly in small fish and benthic species. This study establishes the first set of scientifically robust, YRB-tailored WQCs, offering a practical basis for precise water quality management. Moreover, prioritized regulation of the discharges of four metals, especially in the middle and upper reaches, is recommended to mitigate ecological and public health risks in the basin.