Leibniz-Institut für Ostseeforschung, Warnemünde
(IOW) (Baltic Sea Research Institute, Warnemünde)
Bundesamtes für Seeschifffahrt und Hydrographie, Hamburg, Rostock
(Federal Maritime and Hydrographic Agency of Germany, Hamburg, Rostock)
(Summary of the Baltic Sea Monitoring 2011, Organic contaminants)
Since 1992 the Leibniz Institute for Baltic Sea Research (IOW) is performing the Baltic monitoring programme on behalf of the Federal Maritime and Hydrographic Agency (BSH) Hamburg and Rostock. In 2008 the monitoring area was redefined: Starting from the Kiel Bight up to the Bornholmsgatt samples were collected in the German Exclusive Economic Zone (EEZ).
To determinate the pollution of the Baltic Sea with organic compounds water samples were taken during a winter expedition in February (RV "Alkor") and during a summer cruise in August 2011 (RV "Elisabeth Mann Borgese"). To collect water samples for PCBs (polychlorinated biphenyls), PAHs (polycyclic
aromatic hydrocarbons) and DDTs (dichlorodiphenyltrichloroethane) a pump/filtration system drawing water from the clean water lines of the research vessels were used (for sampled transects see figure 1). Hereby an in-situ pump system separated dissolved and SPM-associated contaminants. For HCHs (hexachlorocyclohexane) samples were
collected at selected stations (Figure 1) with a 10 l glass bowl sampler from 5 meter depth. In July 2011 seven sediment samples were taken in the area of the German EEZ (Figure 2) and analysed for PCB's, DDT 's and PAH 's.
In 2011 the pollution of the surface water in EEZ of the Baltic Sea shows very low concentrations of all analysed contaminants.
In February 2011 the concentrations of HCH (hexachlorocyclohexane) were slightly lower than in the previous year, the concentrations ranged between 88 - 244 pg/L in the area of the German EEZ.
After a strong decrease of the HCH concentrations between 1975 and 1992 from a maximum of 10 ng/L to a level of 2 ng/L and a period of stagnation from 1992 - 2001 with concentrations around 2 ng/L, the declining trend continues. The results of 2011 at station K4 are in line with this trend; HCH
concentrations from 2 ng/L to lower than 0.3 ng/L were observed (Figure 3).
In February because of mixing, waters with higher salinities but lower HCH-concentrations were observed (Figure 4). The inflow of seawater from the North Sea with higher salinities trough the Kiel Bight (15.3) to the Mecklenburg Bight (11.7) reduced the HCH-concentrations in this area. In July because the mixing regime changed, lower salinities (6.5 - 8.0) with low HCH-concentrations
(alpha-HCH 88 - 103 pg/L, gamma-HCH 105 - 124 pg/L) and higher salinities (10) with slightly higher HCH-concentrations (alpha-HCH 136 pg/L) were observed.
Overall the spatial distribution of HCH in the research area showed a homogeneous distribution. However the winter concentrations were 10 - 35 % higher than the summer concentrations.
In February 2011 with exception of the Oder Bight the contamination of the seawater with DDT (dichlorodiphenyltrichloroethane) and metabolites were under a level of 6 pg/L, whereas in August lower concentrations (<2.4 pg/L) were observed. In the Oder Bight high concentrations were observed, this is connected to the high SPM content (2.45 mg/L) and the corresponding higher concentrations in the particulate phase (p,p'- DDE 11.2 pg/L; p,p'- DDT 9.1 pg/L). Higher concentrations in the dissolved phase (p,p'- DDE
6.0 pg/L; p,p'- DDD 6.4 pg/L) indicating that an input from the river Oder occurred recently.
With exception of the Kiel Bight/Fehmarnbelt the content of dissolved DDT and metabolism showed a significant distinctions between winter and summer; high concentrations in February and low concentrations in August (Figure 5). In February more than two times higher concentrations were found. In the Kiel Bight/Fehmarnbelt no significant differences were observed. Through resuspension and resorption during stormy weather conditions the concentrations of
these substances were higher in the dissolved seawater phase in winter.
No decreasing trend within the dissolved concentrations of DDT and metabolism were observed, but overall the concentrations were on a lower level than 2010. In February 2011 the contents with dissolved p,p'-DDE and p,p'-DDT ranged between 2 - 3 pg/L.
The pollution with HCB (hexachlorbenzen) and PCBs (polychlorinated biphenyls), in the surface water of the research area was on the level of the previous years. The concentrations ranged between 0.5 and 9.7 pg/L. Also like DDT and metabolism higher concentrations with HCB were observed in the Oder Bight.
The regional distribution of dissolved HCB and PCBs in the research area showed no significant differences, only higher concentration of dissolved HCB (11.2 pg/L) were found in the Oder Bight. The regional distribution of particulate HCB and PCBs
were attributed to the SPM content; lower concentrations corresponding with a low SPM content (0.10 mg/L) in the Mecklenburg Bight and higher concentrations with a high SPM load (2.45 mg/L) in the Oder Bight.
Seasonal differences by factor of 2 in the dissolved phase of the seawater were characterized trough higher concentrations of HCB and PCBs in February compared to August 2011.
From 2001 to 2011 a decreasing trend of the polar congeners PCB 28/31 and 52 compared to nonpolar congeners with nCl >4, which are more stable in the environment, were observed. In the Mecklenburg Bight and Arkona Sea concentrations between 0.6 pg/L (PCB 118) and 2.8 pg/L (PCB 28/31)
were found. In the average over the last six years the Arkona Sea showed slightly lower PCB concentrations than the Mecklenburg Bight (Figure 6).
The comparison with data from 1988 (Schulz-Bull, 1995) indicated a reduction of only about 50 percent for all PCB congeners over the 34 years period.
In February 2011 the pollution with PAHs (polycyclic aromatic hydrocarbons) of the surface seawater in the research area was between 0.02 - 3.2 ng/L, whereas in August concentrations between 0.01 - 1,2 ng/L were observed. In February higher concentrations of PAHs
by the factor 2 - 5 were found in the Oder Bight.
The regional distribution of particulate PAHs showed significantly higher concentration in the Oder Bight, from Kiel Bight to the Arkona Sea the content of particulate PAH's was homogeneous.
The regional distribution of dissolved PAHs showed homogeneous concentrations of high volatile PAHs (Phenanthrene, Fluoranthene and Pyrene) in the research area of the EEZ, whereas for medium and low volatile PAHs like Anthracene, Benzo(a)anthracene, Benzo(b)fluoranthene and Benzo(k)fluoranthene in the
Arkona Sea and Oder Bight higher concentrations were observed. The higher content of particulate and dissolved PAH's in February 2011 in the Oder Bight may be caused by an plume with suspended material and fresh water with a high content of PAH's from the river Oder. In 2010 the International Commission for the Protection of the Odra River against Pollution (Bewirtschaftungsplan für die Internationale
Flusseinheit ODER) reported that in 2007 26 of 230 water control stations in the Szczecin Lagoon didn't reach a good chemical quality. Main causes therefore were higher concentrations of heavy metals and polycyclic aromatic hydrocarbons.
Significant differences between winter and summer pollution with dissolved PAHs were recorded (Figure 7), in the winter months multiple times higher concentrations in particular for low volatile PAHs were observed. In the winter and summer months the seasonal composition of the dissolved PAH content showed a different distribution of the single
PAHs. The summer concentrations for Phenanthrene and Anthracene were significantly
higher than during the winter. In contrast the winter contribution of low volatile PAHs was many times higher than in summer (Figure 8). Possible causes of higher winter concentrations and the different composition of the dissolved phase may be an input of residues of fossil fuels through the atmosphere and low
degradations rates through biologic processes.
The pollution of the surface water with dissolved PAHs in the German EEZ was observed between 2002 and 2011, but no significant trend was identified. The Mecklenburg Bight showed lower concentrations than in the previous year. Especially the concentration of low volatile PAHs like Benzo(a)pyrene, Indeno(1,2,3-c,d) pyrene and Benzo(g,h,i)perylene were under
the detection limit of 5 pg/L. In the Arkona Sea the content of dissolved PAH's was with exception of Anthracene and Benzo(a)anthracene at a slightly lower level than during the previous year. From 2001 to 2011 in both research areas the content for high and medium volatile PAHs ranged between 0.5 - 1.5 ng/L and the low volatile PAHs were on a level of 0.05 ng/L.
In July 2011 seven surface sediment samples were collected for CB's and PAH analysis from the area Kiel Bight up to Oder Bight. The contamination with organic pollutants was not uniform (Figure 9); high concentrations with PCB, DDE, DDD
and DDT (300 - 3040 pg/g) were observed at stations with high organic carbon content (Arkona Basin: TF0110 - 6.09 %, K7 - 6.30 %). Very low concentrations (25 - 146 pg/g) at station N3 (Kiel Bight), K8 (northwest Hiddensee) and in the Oder Bight can be explained by the sandy sediment and its very low organic carbon content.
The concentrations were partially under the detection limit of 20 pg/g. With exception of p,p'-DDE no CB's were found at station K8, reaching to the question if this station still should be sampled for organic compounds.
In relation to the Corg content (Figure 10) no regional variations were observed: the pollution of the sediments with CB's was homogeneous, the content of CB's ranged between 10 - 30 ng/g TOC. From 2001 to 2011 at all stations no significant trend
The pollution of the surface sediment samples with PAHs ranged between 0.5 and 342 ng/g, with a similar spatial distribution like CB's (Figure 11). In relation to the Corg content distinct regional variations were observed: higher concentrations in the Mecklenburg Bight (M2) and in the Arkona Basin (K7, TF0110), a lower content
of PAHs at stations N3, K8 and ODER. In relation to the organic carbon content a regional pattern can be recognized; higher concentrations in the Mecklenburg Bight (M2) Arkona Basin (K7, TF0110) and northwest Hiddensee (K8) and a lower content of PAH in the Kiel Bight (N3), Fehmarnbelt (N1) and Oder Bight (ODER). Different processes like combustion processes and photochemical/biochemical processes influence
the content of PAHs. Clear trends are not expected, but relatively large fluctuations over time. This can be seen at station K7 in the western Arkona Basin: after low concentrations of PAHs in 2004/2005 a period of 4 years with high concentrations followed by very low concentrations in 2010. In 2011 finally a higher content of PAHs was observed.
The content of organic carbon was on an average of 6 %.
Figure 1:Sampling stations in February and August 2011:
Sampled stations and pump-sampling transects I - IV. (January/February - black; July - red)
Figure 2: Distribution of sediment sampling stations in July 2011.
Figure 3: HCH concentrations (ng/L) at station 109 (Arkona Sea) between 1975 and 2011.
Figure 4: Relationship between salinity and HCH-concentrations.
Figure 5: Comparison of DDT and metabolite concentrations in the dissolved phase in February and August 2011.
Figure 6: Time series of ∑ PCB (dissolved), 2001 - 2011 (January/February), for Mecklenburg Bight and Arkona Sea
Figure 7: Comparison of PAH concentrations in the dissolved phase between February and August 2011.
Figure 8: Comparison of % concentration in the dissolved phase of PAHs between February and August 2011.
Figure 9: HCB, PCB, p,p'-DDE and p,p'-DDD concentrations ( pg/g TS) in surface sediments in July 2011, DS: dry substance.
Figure 10: HCB, PCB, p,p'- DDE and p,p'- DDD contents in relation to the organic carbon content in surface sediments in July 2011.
Figure 11: PAH concentrations in surface sediments at 7 BLMP stations (July 2011).