Langtransport og avsetning av organiske miljøgifter i nordvestlige Europa

Abstract

Persistent organic pollutant (POPs) are toxic compounds which typically consist of one or more groups of hydrocarbons that are aromatic or aliphatic as well as halogenated (chlorine, bromine, fluorine). POPs are normally characterized by low water-solubility and a lipophilic nature, hence they are susceptible for accumulation in fatty tissues. Usually, POPs are semi-volatile and persistent in both air as well as in other environmental media and therefore able to undergo longrange atmospheric transport. POPs may therefore deposit in remote and pristine environments (i.e. the Arctic), far away from any point sources. The focus of this thesis is on selected POPs, which are regulated by international agreements. A specific aim of this thesis was to increase the understanding of the distribution of some legacy POPs in air, by use of a passive air sampling technique, active air samplers (AAS), and an atmospheric transport model (FLEXPART). Passive air samplers (PAS) were deployed at 86 European background stations in 34 countries, mainly utilizing the established EMEP measurement network. The results document spatial variability of legacy POPs and their distribution largely reflects historical and contemporary source regions in Europe. Parallel to the European background site campaign, passive air samples were collected in rural Norwegian coastal zones with dietary advisories on seafood because of elevated levels of POPs. By combining results from these two campaigns, it was possible to evaluate whether local sources or long-range atmospheric transport mainly control the atmospheric POP burdens in contaminated coastal zones. The results documented that some Norwegian coastal zones are strongly influenced by local emission sources of regulated POPs. Furthermore, a model-based forecast system has been developed and evaluated, attempting to predict long-range atmospheric transport (LRAT) episodes to background areas. The forecast system was evaluated for PCBs (polychlorinated biphenyls) at Birkenes by carrying out targeted sampling under predicted LRAT episodes throughout a year (events with expected high concentrations). Measured concentrations in air from the targeted sampling revealed that the model system was largely able to predict LRAT episodes, in addition to identifying the main source areas affecting the site. The study illustrates that a model based forecast system has the potential to complement existing monitoring programmes for POPs in air. The thesis also assesses the occurrence and distribution of “newly regulated” POPs (i.e. pentachlorobenzene (PeCB), endosulfans and short-chain chlorinated paraffins (SCCPs)) in environmental surface media. Soil samples were collected from background areas along a transect from England to Norway. The highest concentrations were found for SCCPs, followed by endosulfans and PeCB. The concentrations of SCCPs were highest near assumed source regions in southern areas, whereas endosulfans and PeCB were more evenly distributed along the transect. Furthermore, endosulfans and PeCB showed many similarities in their spatial pattern, and also with other legacy POPs as previously reported. Endosulfans often peaked in areas with elevated precipitation rates, whereas endosulfan sulfate was the predominant component within the group. PeCB correlated with black carbon in soils, and we therefore believe combustion processes is a key source of PeCB to the atmosphere. The soil survey furthermore illustrated how simple distribution and mobility maps may provide additional mechanistic information to assess the environmental fate and distribution in soils beyond the statistical analyses performed.