Contents And Distribution Of PCBs And Heavy Metals In Surface Sediments From Bering Sea, Chukchi Sea And Canada Basin

During July-September 2008,the 3^rd Chinese National Arctic Research Expedition took place.24 surface sediment samples were collected from Bering sea, Chukchi sea and Canada Basin which were analyzed for 7 heavy metals and 14 PCBs congeners.PCBs concentrations in study area ranged from 21.94 to 639.26 pg/g dw.The∑PCBs values are from 21.94 to 152.25 pg/g dw,60.55 to 639.26 pg/g dw and 23.66 to 604.86 pg/g dw in surface sediments from Bering sea,Chukchi sea and Canada Basin,respectively.Compared with other marginal seas around the world and studies in the Arctic,∑PCBs in study area is much lower.There is a spatial variation for∑PCBs contents in this study and the trend in a increasing order is as following: Canada Basin,Bering sea and Chukchi sea.Tri-PCBs are the controlling homologue at all stations,accounting for 44%to 95%of the total PCBs,which means that Global fractioning influenced the distribution of PCBs in study area.Principal components analysis is used to determine routes of different homologues.The atmospheric long-range transport is a more efficient pathway for tri-PCBs,while most of hepta- and deca-PCBs enter study areas by ocean currents and sea-ice transport.The dominant source of penta- and hexa-PCBs is terrestrial input.The positive correlation is demonstrated among PCBs homologues,total organic carbon(TOC) and black carbon(BC).The relationship is weaken as chlorine atomicity increasing,indicating that organic contents can also influence PCBs distributions in surface sediments.It is found that contents of 7 heavy metals in surface sediments from study area are in the following ranges:21.06 mg/kg to 168.21 mg/kg for Zn(averaged 97.18 mg/kg),8.91 mg/kg - 46.94 mg/kg for Cr(averaged 28.69 mg/kg),2.69 mg/kg-49.39 mg/kg(averaged 19.30 mg/kg) for Cu,32.46 mg/kg - 185.54 mg/kg for V (averaged 99.80 mg/kg),0.09 mg/kg - 0.92 mg/kg for Cd(averaged 0.28 mg/kg), 0.95 mg/kg - 15.25 mg/kg for Pb(averaged 5.58 mg/kg),83.16 mg/kg- 11445.27mg/kg for Mn(averaged 1740.90 mg/kg).The distributions of heavy metals in the surface sediments show a trend that concentrations rise with the latitude grows. High heavy metal values locate at the north of Chukchi Sea and coastal areas along Alasca.The concentrations of the heavy metals in the surface sediments decrease with the increase of grain size of sediments.There is a notable positive correlation between heavy metals and clay contents and the correlation is poor between heavy metals and organic carbon contents.This is because many confounding factors influence the levels and trends of heavy metals in surface sediments in this study.