Sum mary
18
Nordseezustand 2003
els since 1975. The lindane concentration was found to be about 18 % below the prioryear
level. Since 1998, lindane levels have decreased by over 90 %.
Out of the group of unpolar chlorinated hydrocarbons (CHC), the contaminant classes
HCB, PCB, and DDT were investigated. All of the three groups had comparable spatial
distribution patterns in German Bight water, with elevated levels near the coasts. Because
of the high variability of measured values and the relatively short observation
period, no temporal trend has been found either in water or in sediment.
In the North Sea, a background load of aliphatic hydrocarbons (residues of petroleum
hydrocarbons) was identified. Slightly elevated concentrations were found in the German
Bight and in the area of production platforms off the coast of Scotland. However,
natural background levels of aliphatic hydrocarbons from biogenic sources are dominant
in large parts of the North Sea.
Polycyclic aromatic hydrocarbons (PAH, e. g. naphthalene, anthracene, benzo[a]pyrene)
are compounds forming in combustion processes; they are also present
in petroleum products. Most of them are carcinogenic. In water, they showed typical
concentration gradients from the coasts to the open sea, depending on their molecular
size. Elevated levels of naphthalene were found not only in the sea area influenced by
discharges from the Elbe river but also off the Themse estuary, the coast of Scotland,
and the Norwegian coast. Based on the ratios of the individual PAHs in water, it was
possible to identify and explain local hot spots. The highest PAH levels in sediment
were found in the Elbe estuary and in the White Bank area, which is comparable to the
CHC pattern.
Of the 37 polar plant protection agents investigated (insecticides and herbicides), 21
substances were found in the Elbe, and 20 in the German Bight. Usually, these compounds
show a marked annual cycle, which depends on the seasonal use of pesticides
in farming. The herbicides atrazine and simazine were still present at relatively
high concentrations (1 -4ng/L) in the German Bight although their use has been
banned in Germany for several years. Also relatively high levels (1 - 7.5 ng/L) of the
herbicides diurone and isoproturone were found. TBT, a compound used in ship paints
which has hormone-disrupting properties even at extremely low concentrations, still is
of high ecological relevance. The concentrations of 1 - 2 ng/L observed in coastal water
have already reached the toxic threshold level.
Metals
The concentrations of some metals in coastal water, and locally in sediment, were still
far above the natural background levels in some areas. Cadmium, copper, mercury,
lead, and zinc in the dissolved phase showed a strong concentration gradient from the
coast to the open sea, like most organic contaminants. The highest levels were measured
in the area of the Elbe estuary and along the North Frisian coast. Near the coast,
the background levels of all of the above elements were clearly exceeded; in the open
North Sea, only the copper concentrations were elevated. Compared to the preceding
years, however, the metal concentrations in water were not unusually high.
The highest metal concentrations were observed in fine-grained surface sediments
southeast of Helgoland and in the area of the White Bank, where fine-grained sediments
prevail. Metal concentrations in the study area were found to be mostly stagnant
or to have a downward trend. In 2003, following the 1999 - 2002 phase of mark
