title: Temporal trends of PCDD/Fs in Baltic Sea sediment cores covering the 20th century.
abstract: 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.
authors.affiliation: Department of Chemistry, Umeå University , SE-901 87 Umeå, Sweden.
authors.forename: Anteneh T
authors.initials: AT
authors.lastname: Assefa
authors.forename: Anna
authors.initials: A
authors.lastname: Sobek
authors.forename: Kristina L
authors.initials: KL
authors.lastname: Sundqvist
authors.forename: Ingemar
authors.initials: I
authors.lastname: Cato
authors.forename: Per
authors.initials: P
authors.lastname: Jonsson
authors.forename: Mats
authors.initials: M
authors.lastname: Tysklind
authors.forename: Karin
authors.initials: K
authors.lastname: Wiberg
mesh_terms: D000393:Air Pollutants / Q000032:analysis; D001572:Benzofurans / Q000032:analysis*; D005843:Geography; D019015:Geologic Sediments / Q000737:chemistry*; D006207:Half-Life; D049673:History, 20th Century; D009792:Oceans and Seas; D010944:Plants / Q000737:chemistry; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000032:analysis; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000266:history*
chemical_list: D000393:Air Pollutants; D001572:Benzofurans; D000072317:Polychlorinated Dibenzodioxins; D014874:Water Pollutants, Chemical; C023614:dibenzofuran