Marine Chemistry 
Nordseezustand 2004 
25 
Organic Pollutants 
In May and July / August of 2004, samples of sea water, suspended particulate matter, 
and sediment were taken in the German Bight and analyzed for up to 120 different or 
ganic compounds. The main input source of most pollutants is the Elbe River. At 
present, assessments of pollutant levels in sea water are more easy than in sediments. 
Moreover, robust trends in concentration cannot currently be identified for the majority 
of organic substances as time series still are too short and/or spatiotemporal variabil 
ities are very high. 
The main difference in spatial distribution patterns of many substances is due to the 
degree of decline in concentrations from the coast towards the open sea. Concentra 
tion gradients of non-polar pollutants - such as chlorinated hydrocarbons (CHC), HCB, 
PCB, and DDT or polycondensed polycyclic aromatic hydrocarbons (PAH) - are con 
siderably steeper than those of polar organic substances. The differences in slope 
arise from the affinity of the former to adsorb to suspended particulate matter, which in 
turn tends to precipitate to the sea floor at short distances along the path of spread. 
By contrast, polar organic substances are encountered at high concentrations in sea 
water beyond the Elbe River plume. 
In the German Bight, concentrations of the (relatively polar) hexachlorocyclohexane 
isomers a- and y-HCH dropped strongly in the period 1989 - 2004. Levels of a-HCH 
decreased by half every four years. Though y-HCH levels had decreased very slowly 
until about 1998, they dropped by half every two years since then. Meanwhile, concen 
trations of both isomers are well below 0.5 ng/L. These long-term downtrends contin 
ued also in 2004 at the majority of monitoring stations in the German Bight, despite 
the fact that there were up to tenfold higher concentrations of a- and p-HCH in the Elbe 
River load. Off the North Frisian coast (Elbe River plume), however, unchanged or in 
creased concentrations of a-HCH were found in 2004. 
In view of 86 reported cases of oil pollution in 2004, the presence of a basic level of 
aliphatic hydrocarbon pollution (alkanes, residues of petroleum hydrocarbons) had 
been expected and was confirmed by measurements. However, in large parts of the 
German Bight, individual alkanes originating from biogenic sources, in particular al 
gae, were found to predominate. 
The spectrum of polycyclic aromatic hydrocarbons (PAH, e. g. naphthalene, anthra 
cene, benzo[a]pyrene) showed combustion residues of fossil fuels (coal, oil, wood) as 
the main source. Concentration gradients of PAH in sea water were found to become 
steeper toward the open sea with increasing molecular size. PAH levels were in the 
range of variability of preceding years and showed no trends of note. 
Although lipophilic pollutants occur in sediments at concentrations exceeding those in 
sea water about 10 4 - to 10 6 -fold, hardly any source correlations or temporal trends can 
be identified. Relating concentrations to total organic carbon (TOC) instead of dry 
weight (DW) did not, generally, yield a much better assessable picture. Highest levels 
of both, CHC and PAH, were measured at stations around the Elbe River estuary and 
the White Bank where sediments contain high proportions of mud. By contrast, con 
centrations at sites with an abundance of sand were found to be very low. 
Thanks to improved analytical methods, a large number of polar pollutants, specifically 
pesticides, can now be detected. These compounds, which have been monitored rou 
tinely since the year 2000, often have substantially higher concentrations in sea water 
than conventional lipophilic pollutants. In addition, many of them undergo a marked