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- Armitage, James M., 1974-
(author)
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Modeling the global fate and transport of perfluoroalkylated substances (PFAS)
- 2009
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Doctoral thesis (other academic/artistic)abstract
- Perfluoroalkylated substances (PFAS) are persistent contaminants that are widely distributed in the global environment. Despite the fact that these chemicals have been manufactured and used for over 50 years, there has been little scientific and regulatory interest until very recently. An important research priority over the past decade has been to gain a better understanding of the mechanisms and pathways explaining the presence of these compounds in remote regions. One explanation is related to the use and release of volatile precursor compounds which undergo atmospheric transport and are also susceptible to degradation to PFAS through gas phase reactions with radical species. The main purpose of this doctoral thesis was to investigate an alternative explanation, namely the long-range transport (LRT) of PFAS themselves, which have been released into the environment in substantial quantities during manufacturing and product use. Papers I – III explore the LRT potential of perfluorocarboxylic acids and perfluorocarboxylates and demonstrate that both oceanic and atmospheric transport are efficient pathways of dispersion from source to remote regions of the Northern Hemisphere. Oceanic transport of perfluorooctane sulfonate (PFOS) was shown to be an important process in Paper IV as well. The role of precursor transport and degradation to PFOS was also examined in this paper. The most interesting aspect of the fate and transport of PFOS precursors is the rapid response in ambient concentrations exhibited by these compounds in the model simulations following production phase-out. Since precursor compounds are known to degrade to PFOS in vivo, the modeling results demonstrate that this exposure pathway is a plausible explanation for the declining trends in PFOS concentrations reported for marine mammals in some remote environments.
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- Öster, Mathias, et al.
(author)
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Dispersal and establishment limitation reduces the potential for successful restoration of species-rich grasslands on former arable fields
- 2009
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In: Journal of Applied Ecology. - 0021-8901 .- 1365-2664. ; 46:6, s. 1266-1274
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Journal article (peer-reviewed)abstract
- 1. Ex-arable fields have been suggested as potential sites for re-creation of semi-natural grasslands, but information is still limited on the temporal scales needed for the natural assembly of these communities and whether colonization is related to dispersal or establishment limitation. 2. We investigated grazed ex-arable fields of different age and adjacent semi-natural grasslands in terms of species richness of plants, community similarity, colonization pattern and recruitment ability of 16 sown grassland species. The functional trait distribution of successful and unsuccessful colonizing species was compared using five traits related to dispersal and persistence: seed mass, seed bank persistence, specific leaf area, plant height and potential for lateral spread. 3. The youngest ex-arable fields had the lowest species richness and contained communities with the lowest similarity to semi-natural grassland. Species richness and similarity to semi-natural grassland both increased with time since grazing started on ex-arable fields, but were still significantly lower than in semi-natural grasslands even after more than 50 years of grazing. 4. Colonization was not related to any of the investigated functional traits. The rank order of the species in terms of abundance was correlated between young and old ex-arable fields suggesting that species performance remains the same with field age. 5. Recruitment after sowing was generally lower in ex-arable fields than in semi-natural grasslands, although the basic recruitment ability varied between species. Recruitment did not change with field age, suggesting that dispersal limitation rather than establishment limitation caused the temporal pattern of colonization. However, establishment limitation may act as a filter for colonization of all ex-arable fields, regardless of their age. 6. Synthesis and applications. This study demonstrates that the temporal scale for natural assembly of semi-natural grassland communities in ex-arable fields extends over 50 years, even when source pools are nearby. Results suggest that a field age-independent establishment limitation, combined with dispersal limitation, cause the delayed assembly in ex-arable fields. Management that aims to re-create semi-natural grassland communities in ex-arable fields should consider introducing seeds or improving germination conditions at the sites.
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