Performance of heavy metals in the intertidal zone surface sediments of the Yellow River Estuary under water-sediment regulation scheme.

This study investigates the distribution, sources, and ecological risks of heavy metals (Cr, Cu, Zn, Cd, Pb, and Hg) and metalloid (As) in surface sediments of the Yellow River Estuary intertidal zone during the 2023 water-sediment regulation scheme (WSRS) period (summer) and the non-WSRS period (autumn). The results revealed that metal accumulation in both periods was primarily controlled by the co-adsorption of organic matter and fine particles. Hydrodynamic enhancement during the WSRS period reduced metal accumulation through sediment flushing and dilution, whereas weakened flows in the non-WSRS period promoted metal buildup. Assessment based on the geo-accumulation index (Igeo) and ecological risk index (RI) showed low risks for Cr, Cu, Zn, As, and Pb, while Cd and Hg posed moderate risks. Overall, the ecological risks in the study area remained within a low-risk range. The study highlights WSRS influences on heavy metal behavior and provides a basis for estuarine pollution assessment.