amounts to 3 X 10 14 m 3 , nearly 1 m 3 jm 2 of the ocean surface area, In the western
part of Sweden lower figures were registered, the fall-out of PCB's from the atmosphere amounted to 6-120 J-lgfm 2 per annum, but only 1.2-2.4 J-lgfm 2 DDT per
annum (Sodergren 1972). Similar figures were found for PCB's which accumulate in
sedimentation traps together with particles suspended in the seawater. In the Kiel Bight
the PCB figures are 24-112 J-lgjm 2 per year (Osterroth and Smetacek 1980).
Of course, global figures are still very uncertain and do not represent well-grounded
scientific results. There is also insufficient knowledge about the extent to which DDT
by way of sedimentation is again eliminated from the biosphere, that is, to what
extent it can be found in such ocean sediments as are excluded from the biological
cycle. It is, however, alarming that the figures of different calculations coincide with
each other so that there is an increasing possibility that they might be correct.
An analysis of chlorinated hydrocarbons in seawater is problematic for various
reasons. On the one hand the salty ocean water is a difficult medium for chemists,
and on the other it is not clear in which form DDT, for instance, is found in the seawater. It is certain that only a minor part is really dissolved, if at all, and that the
larger part is either found in the form of aggregates that are fine enough to pass
through filters, or is attached to particles with a diameter of less than 1 J-lm. It is also
known that chlorinated hydrocarbons attach themselves intensively to organic matter
and especially dissolve in fat. This explains the enormous accumulation of chlorinated
hydrocarbons in organisms. In not specially polluted ocean water concentrations of
approximately 0.1-1 ngjl DDT and about 0.5-2 ngjl PCB's have been analyzed.
Higher figures have also been given, but it is questionable whether the analytic
methods were appropriate, and there are also experts who doubt whether all PCB
analyses that state more than 1 ngjl are reliable, simply because from the relatively
low amounts of PCB's produced no higher concentrations can possibly develop in
large areas in the Atlantic and Pacific Ocean (Risebrough et al. 1976a). The present
knowledge on chlorinated hydrocarbon concentrations in seawater is summarized in
Fig. 87.
Instead of analyzing chlorinated hydrocarbons from the very low concentrations in
seawater, it is normally much easier to identify DDT, PCB's, and other compounds
from the higher concentrations which organisms have built up within their tissues.
Concentration factors, however, vary from substance to substance, and from organism species to species; comparisons are therefore difficult to make. Some generalizations are presented in Fig. 64. If one considers results from mussels in the laboratory,
concentration factors are about 10,000 for DDT, about 50,000 for PCB's. However,
if one takes into account analyses from the natural environment, it seems that concentration factors are much higher (Table 28). It may be important that chlorinated
hydrocarbons, aside from seawater, are accumulated from food and from contact
with contaminated suspended particles. Such conditions are difficult to simulate in
the laboratory.
Even if, on the whole, concentrations of chlorinated hydrocarbons in sea birds and
seals seem to be rather uniform throughout the Atlantic and may be even higher in
Arctic latitudes than closer to the European coast (see Chap. 9.2), some regional differences have been observed, apart from high concentrations in organisms from
locally polluted areas (see Chap. 3.3). Seals from the Baltic Sea seem to be specially
177
part of Sweden lower figures were registered, the fall-out of PCB's from the atmosphere amounted to 6-120 J-lgfm 2 per annum, but only 1.2-2.4 J-lgfm 2 DDT per
annum (Sodergren 1972). Similar figures were found for PCB's which accumulate in
sedimentation traps together with particles suspended in the seawater. In the Kiel Bight
the PCB figures are 24-112 J-lgjm 2 per year (Osterroth and Smetacek 1980).
Of course, global figures are still very uncertain and do not represent well-grounded
scientific results. There is also insufficient knowledge about the extent to which DDT
by way of sedimentation is again eliminated from the biosphere, that is, to what
extent it can be found in such ocean sediments as are excluded from the biological
cycle. It is, however, alarming that the figures of different calculations coincide with
each other so that there is an increasing possibility that they might be correct.
An analysis of chlorinated hydrocarbons in seawater is problematic for various
reasons. On the one hand the salty ocean water is a difficult medium for chemists,
and on the other it is not clear in which form DDT, for instance, is found in the seawater. It is certain that only a minor part is really dissolved, if at all, and that the
larger part is either found in the form of aggregates that are fine enough to pass
through filters, or is attached to particles with a diameter of less than 1 J-lm. It is also
known that chlorinated hydrocarbons attach themselves intensively to organic matter
and especially dissolve in fat. This explains the enormous accumulation of chlorinated
hydrocarbons in organisms. In not specially polluted ocean water concentrations of
approximately 0.1-1 ngjl DDT and about 0.5-2 ngjl PCB's have been analyzed.
Higher figures have also been given, but it is questionable whether the analytic
methods were appropriate, and there are also experts who doubt whether all PCB
analyses that state more than 1 ngjl are reliable, simply because from the relatively
low amounts of PCB's produced no higher concentrations can possibly develop in
large areas in the Atlantic and Pacific Ocean (Risebrough et al. 1976a). The present
knowledge on chlorinated hydrocarbon concentrations in seawater is summarized in
Fig. 87.
Instead of analyzing chlorinated hydrocarbons from the very low concentrations in
seawater, it is normally much easier to identify DDT, PCB's, and other compounds
from the higher concentrations which organisms have built up within their tissues.
Concentration factors, however, vary from substance to substance, and from organism species to species; comparisons are therefore difficult to make. Some generalizations are presented in Fig. 64. If one considers results from mussels in the laboratory,
concentration factors are about 10,000 for DDT, about 50,000 for PCB's. However,
if one takes into account analyses from the natural environment, it seems that concentration factors are much higher (Table 28). It may be important that chlorinated
hydrocarbons, aside from seawater, are accumulated from food and from contact
with contaminated suspended particles. Such conditions are difficult to simulate in
the laboratory.
Even if, on the whole, concentrations of chlorinated hydrocarbons in sea birds and
seals seem to be rather uniform throughout the Atlantic and may be even higher in
Arctic latitudes than closer to the European coast (see Chap. 9.2), some regional differences have been observed, apart from high concentrations in organisms from
locally polluted areas (see Chap. 3.3). Seals from the Baltic Sea seem to be specially
177