Distribution, enrichment and sources of heavy metals in surface sediments of the North Yellow Sea

The distributions, sources, annual sedimentation and atmospheric deposition flux of heavy metals in surface sediments of the North Yellow Sea (NYS) were investigated. Higher concentrations of the studied metals were generally observed in the western fine-grained sediments and coastal region, and the concentration decreased both in easterly and northerly direction. The sequences of the enrichment factors (EFs) of the studied metals are Pb>Cd>Cu>Zn>Ni>Cr>Co>Mn. The values of EFs suggested that Pb, Cd and Cu in the northwestern region originated from both anthropogenic and natural inputs, while Pb, Cd and Cu in the eastern and northern NYS as well as Zn, Cr, Ni, and Co in the NYS mainly come from natural sources including terrestrial weathering delivered to NYS through rivers and atmospheric deposition. Cu, Cr, Ni and Pb are the four metals with more ecotoxicological concern in the NYS. The annual sedimentation fluxes of heavy metals in the west part of NYS were Fe, 1.34×106 t/yr; Mn, 1.953×104 t/yr; Cu, 9.4×102 t/yr; Zn, 3.09×103 t/yr; Pb, 1.13×103 t/yr; Cd, 4.91 t/yr; Cr, 1.271×104 t/yr; Ni, 1.22×103 t/yr; and Co, 4.9×102 t/yr. Annual dry deposition flux of these metals indicated that the particulate metals (Zn, Pb and Cd) deposition via atmosphere also plays an important role in biogeochemical cycles in the NYS.