100 Years of sediment history of heavy metals in Daya Bay, China

The estuarine and coastal system plays an important role of sedimentation deposition which acts as sink of particle associated contaminants such as heavy metals and polycyclic aromatic hydrocarbons. Sediments conserve important information about past conditions of its aquatic environments. The chronology was developed by using the accumulation rates determined previously from ²¹⁰Pb analyses of the same core. Then, the concentrations of Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn were determined in dated (²¹⁰Pb chronology) sediment cores from four stations (W₀, W₂, W₆, W₉) around the Daya Bay of Guangdong Province (China), where the first nuclear power station of China has been running from 1994. Based on sediment flux (g·cm^-2·year^-1) obtained from the chronologies of ²¹⁰Pbex, the flux of heavy metals were calculated. The increasing of both sediment flux and pollution concentration resulted in the increasing of heavy metals flux (mg·cm ^-2·year^-1) from last century. The experimental data showed that the average values of heavy metals are 18.6, 0.035, 32.9, 38.1, 10.6, 74.9, 4.1, 29.1×10³ and 543 mg/kg for As, Cd, Cr, Pb, Cu, Zn, Co, Fe and Mn, respectively. The concentration of As, Pb, Zn, total organic carbon (TOC) and total nitrogen (TN) in cores are clearly higher than those of natural abundance. Those results indicate that there is pollutant of As, Pb, Zn, TOC and TN in the studying area. The significant relationships between organic C and As, Cr, Pb, Zn, N indicated that such metals are mainly delivered to Daya Bay sediments from a common source.