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Modeling the global fate and transport of perfluoroalkylated substances (PFAS)
Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: Institutionen för tillämpad miljövetenskap (ITM) , 2009. , 32 p.
Keyword [en]
perfluoroalkylated substances, global-scale, fate and transport
National Category
Environmental Sciences
Research subject
Applied Environmental Science
Identifiers
URN: urn:nbn:se:su:diva-8571ISBN: 978-91-7155-812-1 (print)OAI: oai:DiVA.org:su-8571DiVA: diva2:200514
Public defence
2009-03-27, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 8 C, Stockholm, 10:00
Opponent
Supervisors
Available from: 2009-03-05 Created: 2009-02-19Bibliographically approved
List of papers
1. Modeling Global-Scale Fate and Transport of Perfluorooctanoate Emitted from Direct Sources
Open this publication in new window or tab >>Modeling Global-Scale Fate and Transport of Perfluorooctanoate Emitted from Direct Sources
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2006 In: Environmental Science & Technology, ISSN 0013-936X, Vol. 40, no 22, 6969 - 6975 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25782 (URN)
Note
Part of urn:nbn:se:su:diva-8571Available from: 2009-03-05 Created: 2009-02-19Bibliographically approved
2. Modeling the Global Fate and Transport of Perfluorooctanoic Acid (PFOA) and Perfluorooctanoate (PFO) Emitted from Direct Sources Using a Multispecies Mass Balance Model
Open this publication in new window or tab >>Modeling the Global Fate and Transport of Perfluorooctanoic Acid (PFOA) and Perfluorooctanoate (PFO) Emitted from Direct Sources Using a Multispecies Mass Balance Model
2009 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, no 4, 1134-1140 p.Article in journal (Refereed) Published
Abstract [en]

The global-scale fate and transport processes of perfluorooctanoic acid (PFOA) and perfluorooctanoate (PFO) emitted from direct sources were simulated using a multispecies mass balance model over the period 1950 to 2010. The main goal of this study was to assess the atmospheric and oceanic long-range transport potential of direct source emissions and the implications for the contamination of terrestrial and marine systems worldwide. Consistent with previous modeling studies, ocean transport was found to be the dominant pathway for delivering PFO(A) associated with direct sources to the Arctic marine environment, regardless of model assumptions. The modeled concentrations for surface ocean waters were insensitive to assumptions regarding physical−chemical properties and emission mode of entry and were in reasonable agreement with available monitoring data from the Northern Hemisphere. In contrast, model outputs characterizing atmospheric transport potential were highly sensitive to model assumptions, especially the assumed value of the acid dissociation constant (pKa). However, the complete range of model results for scenarios with different assumptions about partitioning and emissions provide evidence that the atmospheric transport of directly emitted PFO(A) can deliver this substance to terrestrial environments distant from sources. Additional studies in remote or isolated terrestrial systems may provide further insight into the scale of contamination actually attributable to direct sources.

Place, publisher, year, edition, pages
American Chemical Society, 2009
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-25783 (URN)10.1021/es802900n (DOI)000263298600030 ()
Note
Part of urn:nbn:se:su:diva-8571Available from: 2009-03-05 Created: 2009-02-19 Last updated: 2011-03-18Bibliographically approved
3. Comparative Assessment of the Global Fate and Transport Pathways of Long-chain Perfluorocarboxylic Acids (PFCAs) and Perfluorocarboxylates (PFCs) Emitted from Direct Sources
Open this publication in new window or tab >>Comparative Assessment of the Global Fate and Transport Pathways of Long-chain Perfluorocarboxylic Acids (PFCAs) and Perfluorocarboxylates (PFCs) Emitted from Direct Sources
2009 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 43, no 15, 5830-5836 p.Article in journal (Refereed) Published
Abstract [en]

A global-scale multispecies mass balance model was used to simulate the long-term fate and transport of perfluorocarboxylic acids (PFCAs) with eight to thirteen carbons (C8−C13) and their conjugate bases, the perfluorocarboxylates (PFCs). The main purpose of this study was to assess the relative long-range transport (LRT) potential of each conjugate pair, collectively termed PFC(A)s, considering emissions from direct sources (i.e., manufacturing and use) only. Overall LRT potential (atmospheric + oceanic) varied as a function of chain length and depended on assumptions regarding pKa and mode of entry. Atmospheric transport makes a relatively higher contribution to overall LRT potential for PFC(A)s with longer chain length, which reflects the increasing trend in the air−water partition coefficient (KAW) of the neutral PFCA species with chain length. Model scenarios using estimated direct emissions of the C8, C9, and C11 PFC(A)s indicate that the mass fluxes to the Arctic marine environment associated with oceanic transport are in excess of mass fluxes from indirect sources (i.e., atmospheric transport of precursor substances such as fluorotelomer alcohols and subsequent degradation to PFCAs). Modeled concentrations of C8 and C9 in the abiotic environment are broadly consistent with available monitoring data in surface ocean waters. Furthermore, the modeled concentration ratios of C8 to C9 are reconcilable with the homologue pattern frequently observed in biota, assuming a positive correlation between bioaccumulation potential and chain length. Modeled concentration ratios of C11 to C10 are more difficult to reconcile with monitoring data in both source and remote regions. Our model results for C11 and C10 therefore imply that either (i) indirect sources are dominant or (ii) estimates of direct emission are not accurate for these homologues.

Place, publisher, year, edition, pages
American Chemical Society, 2009
National Category
Natural Sciences Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-25784 (URN)10.1021/es900753y (DOI)
Note
Part of urn:nbn:se:su:diva-8571Available from: 2009-03-05 Created: 2009-02-19 Last updated: 2011-03-18Bibliographically approved
4. Modeling the Global Fate and Transport of Perfluorooctane Sulfonate (PFOS) and Precursor Compounds in Relation to Temporal Trends in Wildlife Biomonitoring Data
Open this publication in new window or tab >>Modeling the Global Fate and Transport of Perfluorooctane Sulfonate (PFOS) and Precursor Compounds in Relation to Temporal Trends in Wildlife Biomonitoring Data
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Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-25785 (URN)
Note
Part of urn:nbn:se:su:diva-8571Available from: 2009-03-05 Created: 2009-02-19 Last updated: 2010-01-13Bibliographically approved

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