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Assefa, Anteneh T.
Alternative names
Publications (7 of 7) Show all publications
Sobek, A., Sundqvist, K. L., Assefa, A. T. & Wiberg, K. (2015). Baltic Sea sediment records: Unlikely near-future declines in PCBs and HCB. Science of the Total Environment, 518, 8-15
Open this publication in new window or tab >>Baltic Sea sediment records: Unlikely near-future declines in PCBs and HCB
2015 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 518, p. 8-15Article in journal (Refereed) Published
Abstract [en]

We present a comprehensive study on PCBs and HCB in dated sediment cores from the Baltic Sea covering the 20th century, and compare their spatiotemporal trends with those of PCDD/Fs from the same areas. PCB concentrations in coastal impacted sediment followed the temporal trend of estimated global emissions of PCBs and thus responded quickly to changes in global industrial use, whereas concentrations in offshore sediment needed 10-20 years longer to respond. Differences in spatiotemporal trends of PCDD/Fs and PCBs were smaller than expected based on documented differences in key sources and source areas. Sediment concentrations of HCB varied little over time and space, but concentrations are increasing in recent years. The steep PCB concentration reduction over time observed for the late 20th century levelled off during the last 20 years, and levels of PCBs appear to be at or near a steady-state condition. Capsule: PCB concentrations in Baltic Sea sediments appear to be at or near steady-state, and no significant concentration decreases are to be expected in the near future.

Keywords
PCBs, HCB, Baltic Sea, Sediment, Temporal trend, Half lives
National Category
Organic Chemistry
Identifiers
urn:nbn:se:umu:diva-103182 (URN)10.1016/j.scitotenv.2015.02.093 (DOI)000353225700002 ()25747358 (PubMedID)
Funder
Swedish Research Council Formas, 1503601Swedish Environmental Protection Agency, 309-8117-09
Available from: 2015-07-01 Created: 2015-05-18 Last updated: 2018-06-07Bibliographically approved
Assefa, A. (2015). Tracing and apportioning sources of dioxins using multivariate pattern recognition techniques. (Doctoral dissertation). Umeå: Umeå University
Open this publication in new window or tab >>Tracing and apportioning sources of dioxins using multivariate pattern recognition techniques
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

High levels of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in edible fish in the Baltic Sea have raised health concerns in the Baltic region and the rest of Europe. Thus, there are urgent needs to characterize sources in order to formulate effective mitigation strategies. The aim of this thesis is to contribute to a better understanding of past and present sources of PCDD/Fs in the Baltic Sea environment by exploring chemical fingerprints in sediments, air, and biota. The spatial and temporal patterns of PCDD/F distributions in the Baltic Sea during the 20th century were studied in Swedish coastal and offshore sediment cores. The results showed that PCDD/F levels peaked in 1975 (± 7 years) in coastal and 1991 (± 5 years) in offshore areas. The time trends of PCDD/Fs in the sediment cores also showed that environmental half-lives of these pollutants have been shorter in coastal than in offshore areas (15 ± 5 and 29 ± 14 years, respectively). Consequently, there have been remarkable recoveries in coastal areas, but slower recovery in offshore areas with 81 ± 12% and 38 ± 11% reductions from peak levels, respectively.

Source-to-receptor multivariate modeling by Positive Matrix Factorization (PMF) showed that six types of PCDD/F sources are and have been important for the Baltic Sea environment: PCDD/Fs related to i) atmospheric background, ii) thermal processes, iii) manufacture and use of tetra-chlorophenol (TCP) and iv) penta-chlorophenol (PCP), v) industrial use of elementary chlo- rine and the chloralkali-process (Chl), and vi) hexa-CDD sources. The results showed that diffuse sources (i and ii) have consistently contributed >80% of the total amounts in the Southern Baltic Sea. In the Northern Baltic Sea, where the biota is most heavily contaminated, impacts of local sources (TCP, PCP and Chl) have been higher, contributing ca. 50% of total amounts. Among the six sources, only Thermal and chlorophenols (ii-iv) have had major impacts on biota. The impact of thermal sources has, however, been declining as shown from source apportioned time-trend data of PCDD/Fs in Baltic herring. In contrast, impacts of chlorophenol-associated sources generally increased, remained at steady-state or slowly decreased during 1990-2010, suggesting that these sources have substantially contributed to the persistently high levels of PCDD/Fs in Baltic biota.

Atmospheric sources of PCDD/Fs for the Baltic region (Northern Europe) were also investigated, and specifically whether the inclusion of parallel measurements of metals in the analysis of air would help back-tracking sources. PCDD/Fs and metals in high-volume air samples from a rural field station near the shore of the central Baltic Sea were measured. The study focused on the winter season and air from the S and E sectors, as these samples showed elevated levels of PCDD/Fs, particularly PCDFs. Several metals were found to correlate significantly with the PCDFs. The wide range of candidate metals as source markers for PCDD/F emissions, and the lack of an up-to-date extensive compilation of source characteristics for metal emission from vari- ous sources, limited the use of the metals as source markers. The study was not able to pin-point primary PCDD/F sources for Baltic air, but it demonstrated a new promising approach for source tracing of air emissions. The best leads for back-tracking primary sources of atmospheric PCDD/Fs in Baltic air were seasonal trends and PCDD/F congener patterns, pointing at non-industrial related thermal sources related to heating. The non-localized natures of the sources raise challenges for managing the emissions and thus societal efforts are required to better control atmospheric emissions of PCDD/Fs.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. p. 57
Keywords
polychlorinated dibenzo-p-dioxin, polychlorinated dibenzofuran, positive matrix fac- torization, PMF, principal component analysis, PCA, Baltic Sea, sediment core, PCDD/F, sources, marine, fish, environmental half-live, peak year, peak level, temporal trend, spatial variation, coastal, offshore, chemical fingerprint
National Category
Chemical Sciences
Research subject
biology, Environmental Science
Identifiers
urn:nbn:se:umu:diva-102877 (URN)978-91-7601-285-7 (ISBN)
Public defence
2015-06-03, KB3B1 KBC-huset, Umeå University, Umeå, 10:00 (English)
Opponent
Supervisors
Projects
EcoChangeBalticPOPs
Funder
Swedish Environmental Protection Agency, 09/181
Available from: 2015-05-12 Created: 2015-05-08 Last updated: 2018-06-07Bibliographically approved
Assefa, A. T., Tysklind, M., Sobek, A., Sundqvist, K., Geladi, P. & Wiberg, K. (2014). Assessment of PCDD/F Source Contributions in Baltic Sea Sediment Core Records. Environmental Science and Technology, 48(16), 9531-9539
Open this publication in new window or tab >>Assessment of PCDD/F Source Contributions in Baltic Sea Sediment Core Records
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2014 (English)In: Environmental Science and Technology, ISSN 1086-931X, E-ISSN 1520-6912, Vol. 48, no 16, p. 9531-9539Article in journal (Refereed) Published
Abstract [en]

Spatial and temporal trends of sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the Baltic Sea were evaluated by positive matrix factorization (PMF) and principal component analysis (PCA). Sediment cores were sampled at eight coastal, one coastal reference, and six offshore sites covering the northern to the southern Baltic Sea. The cores, which covered the period 1919-2010, were sliced into 2-3 cm disks among which 8-11 disks per core (in total 141 disks) were analyzed for all tetra- through octa-CDD/Fs. Identification and apportionment of PCDD/F sources was carried out using PMF. Five stable model PCDD/F congener patterns were identified, which could be associated with six historically important source types: (i) atmospheric background deposition (ABD), (ii) use and production of penta-chlorophenol (PCP), (iii) use and production of tetra-chlorophenol (TeCP), (iv) high temperature processes (Thermal), (v) hexa-CDD-related sources (HxCDD), and (vi) chlorine-related sources (Chl), all of which were still represented in the surface layers. Overall, the last four decades of the period 1920-2010 have had a substantial influence on the Baltic Sea PCDD/F pollution, with 88 ± 7% of the total amount accumulated during this time. The 1990s was the peak decade for all source types except TeCP, which peaked in the 1980s in the northern Baltic Sea and has still not peaked in the southern part. The combined impact of atmospheric-related emissions (ABD and Thermal) was dominant in the open sea system throughout the study period (1919-2010) and showed a decreasing south to north trend (always >80% in the south and >50% in the north). Accordingly, to further reduce levels of PCDD/Fs in the open Baltic Sea ecosystem, future actions should focus on reducing atmospheric emissions.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-93599 (URN)10.1021/es502352p (DOI)000340701800071 ()
Available from: 2014-09-26 Created: 2014-09-26 Last updated: 2018-06-07Bibliographically approved
Assefa, A. T., Sobek, A., Sundqvist, K. L., Cato, I., Jonsson, P., Tysklind, M. & Wiberg, K. (2014). Temporal Trends of PCDD/Fs in Baltic Sea Sediment Cores Covering the 20th Century. Environmental Science and Technology, 48(2), 947-953
Open this publication in new window or tab >>Temporal Trends of PCDD/Fs in Baltic Sea Sediment Cores Covering the 20th Century
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2014 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 48, no 2, p. 947-953Article in journal (Refereed) Published
Abstract [en]

The pollution trend of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the Baltic Sea region was studied based on depth profiles of PCDD/Fs in sediment cores collected from six offshore areas, eight coastal sites impacted by industrial/urban emissions, and one coastal reference site. A general trend was observed for the offshore and coastal reference sites with substantial increase in PCDD/F concentrations in the mid-late 1970s and peak levels during 1985-2002. The overall peak year for PCDD/Fs in Baltic Sea offshore areas was estimated (using spline-fit modeling) to 1994 ± 5 years, and a half-life in sediments was estimated at 29 ± 11 years. For the industrial/urban impacted coastal sites, the temporal trend was more variable with peak years occurring 1-2 decades earlier compared to offshore areas. The substantial reductions from peak levels (38 ± 11% and 81 ± 12% in offshore and coastal areas, respectively) reflect domestic and international actions taken for reduction of the release of PCDD/Fs to the environment. The modeled overall half-life and reductions of PCDD/Fs in offshore Baltic Sea sediment correspond well to both PCDD/F trends in European lakes without any known direct PCDD/F sources (half-lives 30 and 32 years), and previously modeled reduction in atmospheric deposition of PCDD/Fs to the Baltic Sea since 1990. These observations support previous findings of a common diffuse source, such as long-range air transport of atmospheric emissions, as the prime source of PCDD/Fs to the Baltic Sea region. The half-life of PCDD/Fs in Baltic Sea offshore sediments was estimated to be approximately 2 and 4-6 times longer than in semirural and urban European air, respectively. This study highlights the need for further international actions to reduce the levels of PCDD/Fs in Baltic Sea air specifically and in European air in general.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2014
National Category
Chemical Sciences Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-85509 (URN)10.1021/es404599z (DOI)000330205000015 ()24351230 (PubMedID)
Funder
Swedish Environmental Protection Agency
Available from: 2014-02-05 Created: 2014-02-05 Last updated: 2018-06-08Bibliographically approved
Assefa, A. T., Sundqvist, K., Cato, I., Jonsson, P., Sobek, A., Tysklind, M. & Wiberg, K. (2012). Trends of PCDD/FS in coastal and offshore Baltic Sea sediment cores covering the 20th century. In: : . Paper presented at Dioxin 2012, 26-31 August 2012, Cairns, Queensland, Australia (pp. 328-331). , 74
Open this publication in new window or tab >>Trends of PCDD/FS in coastal and offshore Baltic Sea sediment cores covering the 20th century
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2012 (English)Conference paper, Published paper (Refereed)
Series
Organohalogen Compounds ; vol. 74
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-60815 (URN)
Conference
Dioxin 2012, 26-31 August 2012, Cairns, Queensland, Australia
Available from: 2012-10-31 Created: 2012-10-30 Last updated: 2018-06-08Bibliographically approved
Assefa, A., Tysklind, M. & Wiberg, K. Airborne dioxins and other POPs in the Baltic Sea environment: the potential of using metals as source markers.
Open this publication in new window or tab >>Airborne dioxins and other POPs in the Baltic Sea environment: the potential of using metals as source markers
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Atmospheric sources are major contributors of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the Baltic Sea environment. In this study, we investigated the potential of using trace metals along with PCDD/F levels and seasonal trends as markers of important source types for PCDD/Fs in air. Levels of PCDD/F congeners (n=17) and metals (n=16) were measured in summer and winter air using high volume sampling at a rural field station (Aspvreten, Sweden). During winter, levels were on average 20 times higher than in summer (5.1 ± 5.8 fg TEQ m-3 and 0.26 ± 0.18 fg TEQ m-3, respec- tively) mostly due to a higher fraction of PCDFs. The increased levels were pronounced in air masses from southern (S) and eastern (E) compass sectors. Most of the detected metals (n=12) were positively and significantly correlated with the PCDF congeners for all compass sectors (Cd, Co, Cu, Fe, K, Mn, Pb, Sb, and Zn) during winter season. The average correlation coefficient (r) value for the correlation between PCDF congeners and these metals was 0.85 and p values generally below <0.05. In contrast, polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) showed no significant correlations with detected metals except for HCB and Cr (r=0.60 and p<0.01). The wide range of candidate metals as source markers for PCDD/F emissions, and the lack of an up-to-date extensive compilation of source characteristics for metal emission from various sources, limited the use of the metals as source markers in the current study. Although, the study was not able to pin-point primary PCDD/F sources for Baltic air, we demonstrated a promising approach for source tracing of PCDD/F in air.

Keywords
dioxin, POPs, metal, source, atmospheric, baltic sea
National Category
Chemical Sciences
Research subject
biology, Environmental Science
Identifiers
urn:nbn:se:umu:diva-102867 (URN)
Funder
Swedish Environmental Protection Agency, 09/181
Available from: 2015-05-08 Created: 2015-05-08 Last updated: 2018-06-07
Assefa, A., Tysklind, M., Bignert, A. & Wiberg, K. Source-apportionment shows why dioxin levels have not declined in Baltic fish.
Open this publication in new window or tab >>Source-apportionment shows why dioxin levels have not declined in Baltic fish
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, “dioxins”) in fatty fish of the Baltic Sea have remained high despite declines in environmental levels since the 1980s. This has raised human health concerns and restricted marketing of Baltic herring and salmon within the European Union. Thus, there is an urgent need to identify and control current PCDD/F emission sources. Analysis presented here explains why PCDD/Fs levels in fish have stopped declining or even increased in recent decades. We show that contributions of “thermal” sources (e.g., waste incineration) of PCDD/Fs to Baltic fish have declined since the 1990s, but not contributions of sources associated with the manufacture and use of chlorophenols (particularly tetrachlorophenol and pentachlorophenol, TCP and PCP, respectively). Moreover, the discrepancy between declines in levels of dioxins in abiotic compartments (e.g. sediments and air), and stable or increasing levels in biota can be explained by the persistently high bioavailability of PCDD/Fs associated with TCP and PCP type sources.

Keywords
biota, dioxin, pmf, source, temporal trend, baltic sea
National Category
Chemical Sciences
Research subject
biology, Environmental Science
Identifiers
urn:nbn:se:umu:diva-102868 (URN)
Funder
Swedish Environmental Protection Agency, 09/181
Available from: 2015-05-08 Created: 2015-05-08 Last updated: 2018-06-07
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