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An evaluation of the distributions of polychlorinated biphenyls and organic matter in coastal sediments
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The objective of this thesis is to improve the understanding of what processes and mechanism affects the distribution of polychlorinated biphenyls (PCBs) and organic carbon in coastal sediments. Because of the strong association of hydrophobic organic contaminants (HOCs) such as PCBs with organic matter in the aquatic environment, these two entities are naturally linked. The coastal environment is the most complex and dynamic part of the ocean when it comes to both cycling of organic matter and HOCs. This environment is characterised by the largest fluxes and most diverse sources of both entities. A wide array of methods was used to study these processes throughout this thesis. In the field sites in the Stockholm archipelago of the Baltic proper, bottom sediments and settling particulate matter were retrieved using sediment coring devices and sediment traps from morphometrically and seismically well-characterized locations. In the laboratory, the samples have been analysed for PCBs, stable carbon isotope ratios, carbon-nitrogen atom ratios as well as standard sediment properties. From the fieldwork in the Stockholm Archipelago and the following laboratory work it was concluded that the inner Stockholm archipelago has a low (≈ 4%) trapping efficiency for freshwater-derived organic carbon. The corollary is a large potential for long-range waterborne transport of OC and OC-associated nutrients and hydrophobic organic pollutants from urban Stockholm to more pristine offshore Baltic Sea ecosystems.

Theoretical work has been carried out using Geographical Information Systems (GIS) and statistical methods on a database of 4214 individual sediment samples, each with reported individual PCB congener concentrations. From this work it was concluded that the continental shelf sediments are key global inventories and ultimate sinks of PCBs. Depending on congener, 10-80% of the cumulative historical emissions to the environment are accounted for in continental shelf sediments. Further it was concluded that the many infamous and highly contaminated surface sediments of urban harbours and estuaries of contaminated rivers cannot be of importance as a secondary source to sustain the concentrations observed in remote sediments. Of the global shelf PCB inventory < 1% are in sediments near population centres while ≥ 90% is in remote areas (> 10 km from any dwellings). The remote sub-basin of the North Atlantic Ocean contains approximately half of the global shelf sediment inventory for most of the PCBs studied.

Place, publisher, year, edition, pages
Stockholm: Institutionen för geologi och geokemi , 2004. , 13 p.
Series
Meddelanden från Stockholms universitets institution för geologi och geokemi, ISSN 1101-1599 ; 319
Keyword [en]
Polychlorinated biphenyls (PCBs), organic carbon, sediment, stable carbon isotopes
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:su:diva-125ISBN: 91-7265-884-3 (print)OAI: oai:DiVA.org:su-125DiVA: diva2:189697
Public defence
2004-05-18, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 10:00
Opponent
Supervisors
Available from: 2004-04-27 Created: 2004-04-27Bibliographically approved
List of papers
1. Distribution of PCBs in sediment from different bottom types and water depths in Stockholm Archipelago, Baltic Sea
Open this publication in new window or tab >>Distribution of PCBs in sediment from different bottom types and water depths in Stockholm Archipelago, Baltic Sea
2000 In: Ambio, ISSN 0044-7447, Vol. 29, no 4, 277-281 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-22892 (URN)
Note
Part of urn:nbn:se:su:diva-125Available from: 2004-04-27 Created: 2004-04-27Bibliographically approved
2. Global accounting of PCBs in the continental shelf sediments
Open this publication in new window or tab >>Global accounting of PCBs in the continental shelf sediments
2003 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 37, no 2, 245-255 p.Article in journal (Refereed) Published
Abstract [en]

The recycling longevity of hydrophobic organic contaminants (HOCs) within the global environment is set by their permanent removal through processes such as degradation and burial in geological reservoirs. More than 90% of the global sediment burial of organic carbon (OC) occurs on the continental shelves, representing <10% of the earth's ocean area. The propensity of HOCs to associate with organic matter, and the proximity of most population centers and thus presumed source areas to coastal regions, led us to investigate shelf sediments as a depository of significance for global HOC budgets. Here, the global inventory and burial fluxes of polychlorinated biphenyls (PCBs) in continental shelf sediments were estimated on a congener-specific basis from a database of 4214 distinct continental shelf surface sediment samples. To account for near-urban sampling bias, the locations of each datum relative to nearest population center were classified as Local (<1 km), Regional (1−10 km), or Remote (>10 km), according to a comprehensive vector map of the world (Digital Chart of the World) in a GIS environment. The global inventory of, for instance, PCB congener 153 was 1200 ton (95% confidence limit maximum: 2100 ton; and minimum 720 ton). The Remote sub-basin of the North Atlantic contains approximately half of the global shelf sediment inventory for most of the PCB congeners studied. The shelf sediment inventories of individual PCB congeners constitute significant fractions of their recently updated cumulative historical global emissions estimates. The estimated inventory in the shelf corresponds to about 10% of maximum emission estimates for lower-chlorinated congeners. However, for the more bioaccumulable, higher-chlorinated, congeners the shelf reservoirs appear to account for up to 80% of the estimated maximum cumulative global emissions. These shelf inventories represent 1−6% of the global industrial production of PCBs. The global burial fluxes were estimated to be on the order of 8−24 ton/yr each for the eight major congeners investigated, again, with the shelf constituting a more significant removal sink of the more chlorinated congeners. The permanent removal into deeper shelf sediments of PCB153 and PCB180 suggests that the global environmental mean residence times of these pollutants are on the order of 110 and 70 years, respectively. Hence, even after production and direct releases have been halted, we may expect to be exposed to such persistent pollutants for decades and centuries to come.

National Category
Natural Sciences
Identifiers
urn:nbn:se:su:diva-22893 (URN)10.1021/es0201404 (DOI)
Available from: 2004-04-27 Created: 2004-04-27 Last updated: 2017-12-13Bibliographically approved
3. Evaluation of the Stockholm archipelago, northwestern Baltic Sea proper, as a trap for freshwater-runoff organic carbon
Open this publication in new window or tab >>Evaluation of the Stockholm archipelago, northwestern Baltic Sea proper, as a trap for freshwater-runoff organic carbon
Show others...
2005 (English)In: Journal of Marine Systems, ISSN 0924-7963, E-ISSN 1879-1573, Vol. 56, no 1-2, 167-178 p.Article in journal (Refereed) Published
Abstract [en]

Time-series data on the freshwater inflow of total organic carbon (TOC) to the Stockholm Archipelago, Baltic Sea, covering four full years, showed a distinct seasonal pattern with six times higher monthly flow in winter–spring than in the summer with an annual freshwater TOC input of 28 Gg year−1. Estimation of burial flux and source apportionment of sedimentary OC in the Inner Archipelago (IA) was based on extensive sediment sampling of seismically surveyed accumulation bottom areas. The resulting IA-averaged OC content was 56±16 mg g dw−1 sediment, yielding an IA-wide bottom sediment deposition for the 1992–1995 period of 3.1 Gg year−1.

The sediments in the eastern Lake Mälaren (LM), IA, and Outer Archipelago (OA) were geochemically distinguishable based on their stable carbon isotope signatures (δ13C). The δ13C values were −28.2±0.6, −25.4±1.0, and −23.6±0.3, respectively, for LM (n=15), IA (n=17), and OA (n=31). These spatial trends were consistent with the C:N ratios, which were 9.96±1.2, 9.29±0.73, and 9.13±0.22 for the same subsystems. Using a simple isotopic mass balance model, it was deduced that about one-third (39%) of the OC burial in the IA sediments was of Lake Mälaren runoff origin.

Hence, a low archipelago-trapping efficiency of only 4% for the runoff TOC was found to be accumulating in the sediments underlying the approximately 30 km transect through the IA eastward of Stockholm. This scenario suggests that the organic matter and associated substances added by the Lake Mälaren outflow, passing through urban Stockholm, are largely either remineralised and released to the IA water column, or transported with the currents to more pristine offshore Baltic ecosystems.

Keyword
Urban estuary, Carbon burial, Stable carbon isotopes
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-22894 (URN)10.1016/j.jmarsys.2004.11.001 (DOI)
Available from: 2004-04-27 Created: 2004-04-27 Last updated: 2017-12-13Bibliographically approved
4. Sources and seasonal processing of sediment-trap collected particulate organic matter in the Stockholm Archipelago water column, Northwestern Baltic Sea proper
Open this publication in new window or tab >>Sources and seasonal processing of sediment-trap collected particulate organic matter in the Stockholm Archipelago water column, Northwestern Baltic Sea proper
(English)In: Journal of Sea Research, ISSN 1385-1101, E-ISSN 1873-1414Article in journal (Refereed) Submitted
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:su:diva-22895 (URN)
Available from: 2004-04-27 Created: 2004-04-27 Last updated: 2017-12-13Bibliographically approved

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