Distribution And Significance Of Organophosphate Esters In The Boundary Layer Of The Southern Ocean And On The East Antarctic Ice Sheet

In modern society, plastic products are important in industry and everyday life. In order to improve the properties of plastic, especially to reduce the risk of inflammation, many kinds of flame retardants and plasticizers are added in plastic products. So far, more and more countries and regions have prohibited the consumption of polybrominated diphenyl ethers (PBDEs) flame retardants. As major alternative products, the production and consumption of organophosphorus esters (OPEs) are increasing quickly in the last two decades. However, recent research has discovered biological toxicity of OPEs, which is similar to PBDEs, raising more and more attentions in environmental study. Nevertheless, current study on OPEs mainly focuses on inland and offshore area of Europe and North America, knowledge in the Southern Hemisphere and Asia is very limited, the transport mode is also unclear. Thus it can fill the knowledge gap in global OPE distribution to investigate OPEs in the Southern Hemisphere and ocean areas. Based on this, the long range transport modes of OPEs can be revealed, and consequently providing the scientific basis in evaluating and monitoring the global OPE pollution.In this dissertation, we chose several representative areas in the Southern Hemisphere as our study areas, including the major transect on East Antarctic Ice Sheet (from the Larsemann Hills to Dome A), the Glove Mountains and circumpolar area in the Southern Ocean, and investigated the distribution of multiple OPEs in aerosol and snow samples of these areas. Based on these results, we discussed the factors impacting the OPE distribution in the Southern Hemisphere, and studied the possible transport modes of OPEs. Furthermore, we investigated the OPE records in snow pits with bio-geological principles, and brought forward the bio-geological importance of OPEs in the Antarctic ice sheet as bio-indicators. The major contents and results in this dissertation are listed below.1. OPE pollution was detected in the West Pacific, the East Indian Ocean, the Southern Ocean and the East Antarctic Ice Sheet. We reported first ever OPE detection in inland area of Antarctic ice sheet, and first ever circumpolar OPE investigation in the Southern Ocean. TCEP was found till75°S These results suggested that OPEs are now global contaminations.2. We compared the OPE contamination between the Southern Hemisphere and the Northern Hemisphere, as well as between the offshore areas and ocean areas, it is generally that OPE distribution pattern is high in the north and offshore area and low in the south and ocean area. The average concentration in intense populated areas in the north is one or two magnitudes higher than that in open waters in the Southern Ocean. Furthermore, the back trajectory analysis of air mass indicated that human activities are major source of OPE pollution. The main reason of OPE pollution in the samples is the air mass origin in intense populated areas, while the OPE pollution is obviously lower in air mass originated from open waters. This result also suggest that the major source of OPEs is human activity.3. We hypothesize that ocean gyres could be hot spot of pollution. We calculated average curls in open waters of sample areas based on surface current data and compared them with OPE distribution. The result suggests that OPE concentrations in open waters are positively correlated with average curls of surface ocean currents. This correlation indicates the transport mode of OPEs. As semi-volatile compounds, OPEs cannot make long range transport via atmospheric circulation, but plastic debris containing OPEs can long range transport via surface ocean currents and then accumulate in surface gyres. OPE pollution in the open waters may originate from plastic debris in surface gyres.4. By investigating OPE distribution in surface snow samples and aerosol samples in the Grove Mountains, we discovered that OPEs mainly transport by atmosphere in the Antarctic ice sheet area, and they are probably carried by aerosol particles. OPEs in snow samples may experience post-deposition progresses. OPEs are concentrated in areas with low accumulation rates, while diluted in areas with high accumulation rates. This is of importance in explaining and comparing organic pollution records in snow cores and ice cores.5. We investigated TCEP distribution in surface snow samples of a transect in East Antarctic Ice Sheet (from the Larsemann Hills to Dome A), and discovered that TCEP cannot be quantified in samples from650km farther from the coast, while it can be quantified in almost every sample within650km from the coast. Comparing with previous research, this result suggests different mass origin between inland part and coastal part of the Antarctic ice sheet. The mass origin of inland part is from long range transport via large scale atmospheric circulation, OPEs cannot transport in this way. But the mass origin of coastal part is from mesoscale atmospheric circulation, OPEs can transport to Antarctic ice sheet in this way. TCEP concentrations in snow samples within650km from the coast are positively and significantly correlated with elevation, indicating that TCEP distribution in this area is controlled by cold condensation effect.6. We investigated OPE records in multiple snow pit on the East Antarctic Ice Sheet transect (from the Larsemann Hills to Dome A), and found significant annual or interannual variation in OPE concentrations. Furthermore, a snow pit in the key area at about630km from the coast showed sudden change in the record, suggesting that OPEs may indicate the variation in Antarctic atmospheric circulation and mass origin of Antarctic ice sheet.