Characteristics and Sources of Heavy Metals Pollution in Surface Sediments: An Integrated Land–Sea Comparative Analysis in Dingzi Bay, South Yellow Sea

Systematic and scientific assessments on heavy metal pollution are greatly important to protecting the coastal eco-environment. In this paper, the spatial distribution, pollution degree, ecological toxicity and possible sources of eight heavy metal elements collected from the 126 marine and 715 terrestrial surface sediments surrounding Dingzi Bay were analyzed by obtaining concentration measurements. The results revealed that the concentrations of heavy metals followed a pattern: inner bay > terrestrial areas > outer bay. Cr, Ni, Cu, Zn, Cd, Pb, and Hg were found to accumulate in fine particles (0.25 mm and <0.016 mm). Spatial pollution patterns varied from non-polluted to low pollution levels overall, with localized contamination by individual elements. In addition to natural sources, four types of anthropogenic pollution were identified in the marine and terrestrial settings. Agricultural pollution, characterized by As predominance, exerted profound effects on both terrestrial and marine environments. Industrial pollution, featuring Hg dominance, was widespread in land environment and predominantly linked to atmospheric deposition. Traffic pollution, marked by elevated Pb and Cd, was concentrated around factories and densely populated areas. Maritime pollution, comprising Hg, Cr, Cd, and Zn, primarily occurred in the nearshore areas outside the bay. The findings of this study provide scientific data to the authorities in charge of sustainable coastal zone management in the South Yellow Sea.