Distribution and controls of heavy metals and organic matter in the surface sediments of the Southern Yellow Sea, China

Accurate and effective determination of the source of heavy metals is essential for the treatment of marine ecological environments. This article attempts to combine geochemical composition data and hydrocarbon composition data to achieve this purpose. The concentrations of six heavy metals (Cu, Pb, Zn, Cr, Ni, and Co), grain size, total organic carbon (TOC) content, Al2O3 content, and aliphatic hydrocarbons (AHs) in 501 surface samples from the Southern Yellow Sea (SYS) were analyzed. The results showed that most sample sites ranged from not polluted to moderately polluted. However, Cu, Pb, Cr, and Ni may represent potential hazards, and the toxic probability for the combination of five metals (Cr, Cu, Ni, Zn, and Pb) was 21% for all sampling sites. The highest heavy metal concentrations were associated with the fine-grained sediments in the eastern area, especially in the northeastern muddy area. However, high concentrations of Pb and Cu were also found in some sites with coarse sediment in the western region. The lipid biomarkers showed that the n-alkanes were dominated by large odd-numbered carbon molecules, indicating that the organic matter in the sediments originated mainly from terrestrial plants. Principal component analysis (PCA) results, AH data, and the sediment distributions indicated that the organic matter and heavy metals in the SYS were mainly sourced from the Old Yellow River Delta, transported by ocean currents and deposited in the central SYS. In addition, a small proportion of the heavy metals originated from airborne dust. The spatial distribution pattern of the heavy metals in the surface sediments provides a basis for the protection of the marine ecological environments.