Distribution, Source, and Pollution Risk Assessment of Heavy Metals in the Coastal Sediments of the Northern South China Sea.

Heavy metals contamination in coastal sediments poses potential ecological and human health risks due to their persistence, bioaccumulation, and remobilization under changing environmental conditions. In this study, eight heavy metals (Cu, Mn, Zn, V, Cr, Ba, Be, and Ti) were analyzed in 118 sediment samples collected from five representative bays along the northern South China Sea. The concentrations of heavy metals were determined using inductively coupled plasma-optical emission spectrometry (ICP-OES). Multivariate statistical analyses, including correlation analysis, principal component analysis (PCA), and positive matrix factorization (PMF), were applied to elucidate spatial distribution patterns and source contributions. Sediment quality and potential toxicity were assessed using multiple indices-the geoaccumulation index (Igeo), sediment toxicity degree (STd), and toxic equivalent concentration (TEQ). The results indicated that heavy metals contaminations were generally at low to moderate levels, exhibiting significant spatial heterogeneity among bays. Zn, Cu, and Mn were identified as dominant contributors to potential ecological risks, mainly linked to industrial and port-related activities. Human health risk assessment revealed negligible non-carcinogenic risks (hazard index, HI < 1) for both adults and children, although children showed higher cumulative susceptibility. Overall, this study provides an integrated ecological and health risk evaluation of heavy metals in coastal sediments of the northern South China Sea, offering valuable insights for regional pollution control and sustainable coastal management.