Provenance And Historical Deposition Of Metals And Organic Matter In Sediments From The Bering Sea-western Arctic Ocean And The South China Sea

In this research,the content,distribution and provenance of total organic carbon(TOC)and metals(Fe,Mn,Pb,Zn,Cu,Ni)were investigated in several sediments from the Bering Sea-western Arctic Ocean and the western South China Sea(the eastern coast of Vietnam)by 210Pb dating,Pb isotope ratios,C/N and ?13C tracer applications.We compared the metal and TOC historical trends in the western Arctic Ocean and the South China Sea by combining the historical process of local human activities.And then we mainly discuss the main influence factors about the distribution of metals and TOC and the relative contribution of natural and anthropogenic activities to metals and TOC.The major conclusions are summarised as follow:(1)The contents of Ni,Cu,Zn,Pb,Fe and Mn in the surface sediments from the Bering Sea-western Arctic Ocean were ranged from 14.31?76.9 mg/kg,5.51?57.64 mg/kg,62.54?155.84 mg/kg,9.74?31.97 mg/kg,1.94?5.94%and 0.17?12.39 g/kg.And the concentrations of Ni,Pb,Fe,Mn,Cu and Zn in sediment core from the western Arctic Ocean were ranged from 19.36?48.82 mg/kg,15.83?24.72 mg/kg,2.16?5.02%,0.32?8.88 g/kg,12.53?27.63 mg/kg and 75.49?170.41 mg/kg.(2)Pb isotope ratios analysis suggested that the main provenance of metals in the Bering Sea-western Arctic Ocean were bedrock.The historical variation of Pb isotope ratios in the sediment core reflected the influence of global industrial activity,and the results of C/N and 613C suggested that the main source of particle organic carbon is marine input.(3)The concentrations of Pb,Cu,Ni,Zn,Fe and Mn in sediment core from the South China Sea were 9.86?16,95 mg/kg,10.55?22.99 mg/kg,22.84?43.37 mg/kg,68.07?101.43 mg/kg,1.80?3.21%and 0.27?0.58 mg/g,respectively,which were lower than in the Bering Sea-western Arctic Ocean.(4)The results of Pb isotope ratios indicated that the provenance of metals were mainly atmospheric transmission from China,bedrock in the Pearl River Delta,terrigenous inputs from Vietnam.(5)According to the results of C/N and,?13C the origin of organic matter in the South China Sea was mainly autochthonous inputs,which was similarly to the Bering Sea-western Arctic Ocean.The rivers in Vietnam contributed less organic matter to marine than marine phytoplankton(algal)detritus.(6)According to the results of ecological risk assessment in both sea areas,the concentrations of metals in sediment core were the non-pollution and slight enrichment level,which indicated the limited influence from anthropogenic activities,and mainly influence from natural activities in Arctic and the South China Sea.