Distribution and contamination of heavy metals in surface sediments of the Daya Bay and adjacent shelf, China

Heavy metal (arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn)) concentrations from the Daya Bay and adjacent shelf were determined to evaluate their levels and spatial distributions. The measured concentrations ranged from 1.94-13.67 mg/kg for As, 0.03-0.13 mg/kg for Cd, 10-85 mg/kg for Cr, 1-39.5 mg/kg for Cu, 0.01-0.09 mg/kg for Hg, 11-56 mg/kg for Pb, and 13-125 mg/kg for Zn. The spatial distributions exhibited a gradual decrease from west to east, and the concentrations of the seven heavy metals met the China Marine Sediment Quality criteria. Both metal enrichment factor (EF) and geo-accumulation index (Igeo) values showed that Cd, Cr, Cu, Hg, and Zn were not at pollution levels in the region. Multivariate analysis (PCA) revealed that lithogenic factors dominated the distribution of most of the metals, whereas As and Hg were clearly influenced by anthropogenic input.