MURSYS - Baltic Sea





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MURSYS - Baltic Sea

   
 
 

Regional distribution of organic contaminants in the pelagial and the surface sediment of the Baltic in 2006

  Leibniz-Institut für Ostseeforschung, Warnemünde
(IOW) (Baltic Sea Research Institute, Warnemünde)
commissioned by
Bundesamtes für Seeschifffahrt und Hydrographie, Hamburg, Rostock
(Federal Maritime and Hydrographic Agency of Germany, Hamburg, Rostock)

(http://www.io-warnemuende.de/)

(Summary of the Baltic Sea Monitoring 2006, Organic contaminants)

In January 2006 water samples from the Baltic Sea were collected to evaluate long term trends of organic compounds. Along eight transects samples were collected for PCBs (polychlorinated biphenyls), PAHs (polycyclic aromatic hydrocarbons) and DDTs (dichlorodiphenyltrichloroethane) using a pump/filtration system. Hereby an in-situ pump system separated dissolved and SPM-associated contaminants. For HCHs (hexachlorocyclohexane) samples were collected at selected stations from the clean water line in 5 meters depth at stations in the following areas:
Western Baltic, Transect 2: Arkona Sea/Bornholm Sea, Transect 1: Eastern Gotland Sea.

For alpha-HCH the concentrations ranged between 237 pg/L and 350 pg/L, for gamma-HCH between 312 pg/L and 441 pg/L and for beta-HCH between 346 pg/L and 482 pg/L. The spatial distribution of alpha-HCH showed slightly lower concentrations west of Bornholm (237-280 pg/L) than in the Gotland Sea (317 - 329 pg/L), whereas higher concentrations were observed at Station 109 in the Arkona Sea (350 pg/L). For gamma-HCH increasing concentrations from the Mecklenburg Bight (317 pg/L) to the Gotland Sea (441 pg/L) were observed. To estimate long-term trends of the pollution with HCHs, the sampling grid has been changed, the new data set contains results over ten years period. Between 2000 and 2006 the concentration of all 3 HCH congeners decreased by about a factor of 2 in the entire study area.
The vertical distribution of HCHs was measured at 3 stations with a clearly stratified water column (213, 259, 271). In the Bornholm Sea (station 213) the HCH concentrations of all HCH congeners in the deep water were clearly lower than the concentrations in surface water. At Station 259 (SE Gotland Basin) the difference between surface and deep water concentrations of beta-HCH and gamma-HCH was insignificant, whereas the concentration of alpha-HCH in the deep water was clearly higher than in the surface water. In the Gotland Sea at Station 271 the concentrations of alpha-HCH and beta-HCH in the deep water were slightly higher than the concentrations measured in the surface water.

A new dataset of five years with the dissolved concentrations of p,p'-DDE and p,p'-DDT is used to estimate long-term trends in the study area. Since 2003 the exposure of p,p'-DDE has ranged on a level of 4 - 5 pg/L, p,p'-DDT shows a slightly decreasing trend. In 2006 the dissolved concentrations for p,p'-DDT ranged between 1.7 pg/L and 3.0 pg/L, for p,p'-DDE between 2.7 pg/L and 4.7 pg/L, for p,p'-DDD between 2,2 pg/L and 5.1 pg/L. The spatial distribution of DDT and metabolites was characterized by decreasing concentrations from the western Baltic Sea to the Gotland Sea, the highest concentration were observed in the Mecklenburg Bight.

In 2006 the exposure of the surface water with dissolved PCBs was indicated by a slightly decreasing trend (0.2 - 3 pg/L). The dissolved concentrations are better suited for judging the spatial distribution of contamination and for determination of temporal trends. Most of the study area showed homogenous dissolved concentrations, whereas the levels in the western Baltic Sea were slightly higher than in the Gotland Sea. The comparison with the data from 1988 (Schulz-Bull, 1995) indicated for all PCB congeners a reduction of 50 percent.
The pollution of the surface water with dissolved PAHs was observed between 2002-2006, there is no significant trend in the study area. After lower concentrations in the previous year, notably in the Arkona Sea/Bornholm Sea, the PAH concentrations (0.01 - 2.6 ng/L) were found on the level of 2003/2004. For the study area of the Arkona Sea/Bornholm Sea the values show a greater variability. For PAHs with medium and low vapour pressure a approximately constant or a slight decrease was observed in the eastern Gotland Sea.

In November 2006 five sediment samples were collected for PCB and PAH analysis from the area of eastern Baltic Sea and the Arkona Sea. The PCB/DDE concentrations ranged between 8 and 4091 pg/g. The PAH concentrations in the study area ranged between 1 and 462 ng/g with a similar distribution to that of the PCBs. There was a strong correlation between the PCB/PAH concentrations and the Corg content.
Aim of the monitoring research part was to analyse one sediment core in the area of the Arkona Sea and five surface sediment samples for sediment monitoring of polybrominated diphenylethers (PBDEs), especially the development of a GC-MS method to measure PBDE 209. The detektion limit is 100 pg/g sediment. Contrary to expectations PBDE 209 was not detected in the sediment samples.

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