Distribution and environmental quality of trace metal(loid)s in water and surface sediments of northern Liaodong Bay, China

Coastal areas such as bays, characterized by intense land-sea interactions and frequent human activities, are confronting ecological pressures induced by trace metal(loid) pollution in aquatic environments. In this study, trace metal(loid)s (Cu, Pb, Zn, Cr, Cd, and As) in surface water, bottom water, and surface sediments of northern Liaodong Bay were analyzed to assess their spatial distribution, contamination status, and controlling factors. The concentrations and distribution patterns of these metal(loid)s were consistent between surface and bottom water, yet varied substantially among different elements, with high-concentration areas distributed in a patchy manner. All trace metal(loid) concentrations in the water column were within the Class I seawater quality standard. However, no significant correlation was observed between trace metal(loid) contents in sediments and those in the water column (correlation coefficients R 2 are all less than 0.1), and the distribution patterns of individual metal(loid)s in sediments were also inconsistent. Sediments were unpolluted by Cu and Cr, while Pb, Zn, Cd, and As exhibited unpolluted to moderately polluted conditions. Comprehensive evaluation indicated that the overall trace metal(loid) pollution in surface sediments was low. Trace metal(loid)s in both water and sediments were not predominantly controlled by natural processes; instead, point source pollution derived from riverine transport, coastal industrial and agricultural activities, offshore oil extraction, and shipping emerged as a crucial influencing factor. This study provides fundamental data for in-depth research on trace metal(loid) pollution in coastal areas and emphasizes the need for adequate attention to metal(loid) pollution in coastal ecosystems.