zinc
o
10
20
30
200 400
•
-
-
-- ••
-.
-
-
- ...
• •
•
••
-
lead
20 80
160
-
-
••
• • •
• • •
•
• •
- • •
• ••
•••
•••
• •
•
cadmium
OJ 0.8
1.6
• I'"
• •
• •
••
••
. ..
• ••
• •
• ••
•••
-
..
••
• •
-
mercury
0.2 0.8
1.6 mg / kg
••
••
-
• ••
• •
• ••
•
• •
-
• •
-
- -
••
-
•••
•••
-
-
••
•••
-
-
-
• •
•
•
40
60 Ii) ": . II · .. I))' ..
I:::
::<..
•.•••.••
•.•••••••••
. . : ••••
,~: ' ell' M 1 i ==I[
~.
120 ••••••••••••
.<....
. : . . . . . . .
. . . . . :
400 --c::::Je
E!l
~
D
cm
Fig. 73. Concentrations of heavy metals in a sediment core from 22 m water depth in the Bay of
Helgoland, North Sea. The natural rate of sedimentation in this area is approximately 50 cm per
century. The shadowed vertical bars represent as background the heavy metal concentration
before man and his civilization affected it. At a core depth of 125 cm, corresponding approximately to a period of 200-300 years ago, fairly high concentrations of some heavy metals begin
to stand out. There are especially high amounts in the upper 20-40 cm. It has been concluded,
from the chemical form of the heavy metals that atmospheric contribution played the most
important role and that a 3.5-fold increase of the lead concentration and a 2.5-fold increase of
the cadmium concentration has taken place (Patchineelam and Forstner 1977). These conclusions
are not beyond doubt as there are plenty of burrowing macrofauna living in the silty mud of
Helgoland Bight, and as sometimes erosion and subsequent resedimentation of the suspended
sediment occurs and disturbs the stratification. Data represent mg/kg of dry clay fraction of the
sediment with grain sizes less than 2 pm (Forstner and Reineck 1974)
Table 30. Examples of sedimentation rates in various marine areas
(Seibold 1974)
Wadden-Sea
Coral reefs
Oxygen-deficient basins off coast of California
Black Sea
Bay in the Adriatic
Continental slope
Globigerina deep sea clay
Red deep sea clay
Red deep sea clay in Pacific
138
20 cm/year
1 cm/year
2-3 m/millenium
40 cm/millenium
25 cm/millenium
10 cm/millenium
5 cm/millenium
1 cm/millenium
1 mm/millenium
o
10
20
30
200 400
•
-
-
-- ••
-.
-
-
- ...
• •
•
••
-
lead
20 80
160
-
-
••
• • •
• • •
•
• •
- • •
• ••
•••
•••
• •
•
cadmium
OJ 0.8
1.6
• I'"
• •
• •
••
••
. ..
• ••
• •
• ••
•••
-
..
••
• •
-
mercury
0.2 0.8
1.6 mg / kg
••
••
-
• ••
• •
• ••
•
• •
-
• •
-
- -
••
-
•••
•••
-
-
••
•••
-
-
-
• •
•
•
40
60 Ii) ": . II · .. I))' ..
I:::
::<..
•.•••.••
•.•••••••••
. . : ••••
,~: ' ell' M 1 i ==I[
~.
120 ••••••••••••
.<....
. : . . . . . . .
. . . . . :
400 --c::::Je
E!l
~
D
cm
Fig. 73. Concentrations of heavy metals in a sediment core from 22 m water depth in the Bay of
Helgoland, North Sea. The natural rate of sedimentation in this area is approximately 50 cm per
century. The shadowed vertical bars represent as background the heavy metal concentration
before man and his civilization affected it. At a core depth of 125 cm, corresponding approximately to a period of 200-300 years ago, fairly high concentrations of some heavy metals begin
to stand out. There are especially high amounts in the upper 20-40 cm. It has been concluded,
from the chemical form of the heavy metals that atmospheric contribution played the most
important role and that a 3.5-fold increase of the lead concentration and a 2.5-fold increase of
the cadmium concentration has taken place (Patchineelam and Forstner 1977). These conclusions
are not beyond doubt as there are plenty of burrowing macrofauna living in the silty mud of
Helgoland Bight, and as sometimes erosion and subsequent resedimentation of the suspended
sediment occurs and disturbs the stratification. Data represent mg/kg of dry clay fraction of the
sediment with grain sizes less than 2 pm (Forstner and Reineck 1974)
Table 30. Examples of sedimentation rates in various marine areas
(Seibold 1974)
Wadden-Sea
Coral reefs
Oxygen-deficient basins off coast of California
Black Sea
Bay in the Adriatic
Continental slope
Globigerina deep sea clay
Red deep sea clay
Red deep sea clay in Pacific
138
20 cm/year
1 cm/year
2-3 m/millenium
40 cm/millenium
25 cm/millenium
10 cm/millenium
5 cm/millenium
1 cm/millenium
1 mm/millenium