Distributions And Sources Of Polychlorinated Biphenyls In The Yellow Sea And The East China Sea Inner Shelf Sediments

Polychlorinated biphenyls (PCBs), as a kind of typical persistent organicpollutants, are unbiquitous in the general environmental. Ever since the first discoveryof PCBs in environmental samples in the mid-1960s, these contaminants have been atthe center of environmental health attention due to their toxicity, bioaccumulation, andpresumed persistence in the environment. PCBs were not produced in large amount andwere not widely used in China, but their impacts on the environment cannot beneglected. In addition, PCBs are still unintentionally produced and discharged into theenvironment.The Yellow Sea (YS) and the East China Sea (ECS) are typical marginal seas withlarge amount of emissions of land based pollutants. And the environment continuouslydeteriorates especially in recent decades. Therefore, the occurrences, distributions andsources of pollutants in those areas are key factors to understand the relationshipsbetween environment pollution and human activities in the coastal region. In thisresearch, PCBs are chosen as target compounds to indicate the man-made pollutions.For determination of PCBs in marine sediments by gas chromatography, a rapidand effective procedure for simultaneous sample extraction and purification wasestablished, in which an ultrasonically assisted alkaline hydrolysis was combined withsolvent extraction. The organochlorine pesticides (OCPs) can be completelyhydrolyzed under ultrasonic treatment in2.0mol L-1NaOH-methanol solution for10minutes, to realize the elimination of interference from OCPs in determination of PCBswhile extracting PCBs effectively at the same time. Under the optimized conditions,the recoveries of PCB congeners were between72.1%and113.7%and the RSDs werebetween0.4%~6.3%(n=6). It was shown from the chromatograms that the content ofimpurities was reduced significantly and the baseline was improved greatly. All of these can meet the requirements for qualitative and quantitative determination of traceorganics in environmental samples.The Yangtze River estuary (YRE) and the adjacent East China Sea (ECS) innershelf is an important sink of pollutants originated from mainland China. In this work,we studied the spatial and temporal variations and sources of PCBs in sedimentsfromthe YRE and the ECS inner shelf. Total concentration of24PCBs (Σ24PCB) rangedbetween24.3and343.3pg/g (with a mean value of126.7pg/g), and higher valuesoccurred in the estuarine region. The homolog profile was dominated by3–5Cl CBs,accounting for76.1%of Σ24PCB. The Cl proportion ranged from45.1%to58.8%(witha mean value of49.9%); the lowest level appeared in the estuarine region, and itincreased with distance from the YRE. Lower chlorinated congeners were carriedmainly by the YR into the ocean, to be finally buried in sediments of the estuary regionand vicinity. However, higher chlorinated oneswere imported mainly via directemission from local sources, to be finally buried in sediments farther away from theestuary. Of the PCBs in surface sediments,64.4%came from the YR,13.8%from thelocal sources and the rest21.8%from atmospheric deposition.In a sediment core, we found that81%of PCBs were technically produced and19%unintentionally produced in the last century. Before the1970s, PCB levels wereinfluenced predominantly by the production and consumption of technical PCBs. Whilein recent decades, the effect of human activities on PCB levels has been increasingcontinuously.Although there is no direct major riverine input, a large quantity of waste producedin mainland China and Korea is transported continuously to the Yellow Sea (YS)through atmospheric deposition, currents and tides; therefore, the environment isdistinctly influenced by man-made pollution. This study focuses on the associatedpollutant transport mechanisms by sampling PCBs.∑24PCB in YS sediments rangedbetween99pg/g and3.13ng/g of dry sediment (with a mean value of715pg/g). PCBsproduced unintentionally by industrial and other processes appeared to be the majorsource of PCBs in the sediments, accounting for60.5%. Industrially synthesized PCBswith3Cl and5Cl accounted for15.5%and24.0%, respectively. PCBs were mainly from atmospheric deposition (84.5%), followed by continental runoff (15.5%).