| Persistent organic pollutants (POPs) are substances that are persistent and toxic and can affect both humans and wildlife. Once these compounds are released into the environment, they can migrate through the atmosphere and be transported to the regions where these chemicals have never been used, like Arctic, During the long range atmospheric transport, POPs show the tendency to deposit, condense and accumulate in cold Arctic ecosystem. Hence, long range spatial surveys are necessary and effective to understand the large scale distribution, long range atmospheric transport (LRAT) and sources of these substances in the North Pacific Ocean and adjacent Arctic regions. On the other hand, environmental events and climate change in the recent years can alter the exposure levels of marine ecosystems through a variety of means including changes in long range transport and re-emission of these pollutants with the biomass burning and the melting of the sea ice. In order to update the levels of POPs, identify the sources areas and factors influencing the long range atmospheric transport, and reveal the potential influence of environmental events and climate change to the atmospheric levels of these pollutants in the north Pacific Ocean and the adjacent Arctic Ocean, air samples were collected aboard the research expedition icebreaker XueLong (Snow Dragon) as part of the 2008 Chinese Arctic Research Expedition Program. Concentrations of PCBs, HCB, HCHs, DDTs, Chlordanes, HBCD and PBDEs were analyzed in all of the samples.In the current study, levels of HBCDs were less than the limits of detection for all the air samples (particle phase collected with glass fiber filter), indicating that the levels of HBCD in the oceanic atmosphere over North Pacific Ocean and the Arctic Ocean were low and atmosphere may be not the major pathway for the long range transport of HBCD from Eurasia to the Arctic region. Result of PBDEs is still under treatment. Hence, the details are not included in the thesis.ΣPCBs in the atmosphere (PCBs and organochlorine pesticides were detected in gas phase) ranged from 22.0 to 520 pg m-3 with average concentration of 240±160 pg m-3, Tri-PCBs, tetra-PCBs and penta-PCBs were the most abundant homologues that contributed 30±13%,53±13% and 16±6% of total PCBs in all samples. Highest concentration was observed over the Japan Sea, while the lowest concentration was measured at high latitude of the Arctic Ocean. Relatively high levels of PCBs over the North Pacific Ocean were observed in samples collected near land masses. Air mass back trajectories indicated these samples might be influenced by the atmospheric transport of PCBs from nearby source regions. Homologue composition and latitudinal trends of PCBs indicated that during the long range atmospheric transport, the lighter PCB congeners would be transported and deposited in colder regions like the Bering Sea, while the heavier PCB congeners would be deposited closer to sources.HCB was>MDL in all the samples for the cruise and ranged from 24 to 180 pg m-3, with the average concentration of 88 pg m-3.The relatively higher levels of HCB were found in East Asia than those in North Pacific Ocean, indicating that East Asia may be a potential source region of HCB to the North Pacific Ocean. The concentrations of HCB exhibited an increasing trend in North Pacific Ocean and the adjacent Arctic Ocean, indicating the global fractionation of HCB.HCH concentrations were analyzed in all of the samples. The average concentrations over the entire period were 33±16,5.4±3.0, and 13±7.5 pg m-3 for a-β- andγ-HCH, respectively. Compared to previous studies in the same areas, totalΣHCH levels declined by more than ten times compared to those observed in the 1990s, but were approximately four times higher than those measured by the 2003 China Arctic Research Expedition, suggesting the increase of atmosphericΣHCH recently. Because of the continuing use of lindane, ratios ofα/γ-HCH showed an obvious decrease in North Pacific and Arctic region compared with those for 2003 Chinese Arctic Research Expedition.ΣDDTs concentrations over the whole cruise varied substantially, ranging from 2.0 to 110 pg m-3 with the average concentration of 36±31 pg m-3. The fresh inputs of p,p'-DDT and o,p'-DDT indicated by DDT/DDE ratios and the relatively higher levels of p,p'-DDT and o,p'-DDT observed in East Asia and North Pacific Ocean may reflect direct transport of these compounds from the adjacent continent where continuing usage of DDT-related compounds is potentially occurring. The ratios of o,p'-DDT/p,p'-DDT were higher than that in technical DDT but much lower than those observed in air samples from China, indicating the atmosphere during the present study was likely influenced by a mixture of DDT-containing products.The concentrations ofΣchlordanes varied between 1.8 and 11 pg m-3, with an average of 5.4±2.6 pg m-3. Trans-chlordane (TC) and cis-chlordane (CC) were the most abundant among the chlordanes isomers, accounting for 40% and 39% of total chlordane for all samples. The TC/CC ratios measured in all samples were lower than in the technical mixture, reflecting the main influence by weathered chlordane. The sampling sites with low levels of TC and CC often have relatively low TC/CC ratios, and may be influenced by older air masses.As the usage and production of most of POPs have been banned or restricted in a wide range of the world, and significant reductions in primary emissions of these substances recently, the relative importance of secondary re-emission is expected to increase.In the current study, most the organochlorine pesticides presented high levels during the end of July when the sampling ship was sailing over the Bering Sea. Satellite data indicated that there were great fires over the Siberia in July of 2008. Satellite data of smoke emissions, CO distribution and air mass back trajectories were used to indentify the influence of biomass burning emissions to the levels of pesticides in Bering Sea. The result indicated that the occurrences of fires in Siberia during the July of 2008 might make a significant contribution to high levels of DDT and HCH observed in the atmosphere of North Pacific Ocean during our expedition.In Arctic regions, the levels of most organochlorine pollutants in the floating sea ice region were higher than those measures in the open sea area and pack ice region. In the area covered by seasonal and multiyear sea ice, these chemicals showed evidently decreasing trends with the increasing of ice concentration. This phenomenon implies that the volatilization of these pollutants accumulated in snow pack, sea ice, and Arctic Ocean might be accelerated during the summer as ice coverage in the Arctic region decreases in response to global climate change.
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