252
M.E. Farago
Port of Hamburg. Schmidt also reported values of mercury concentrations, in samples
from 10 m depth, carried out in two surveys of the entire North Sea in May/June 1986
and January/March 1987. The first survey showed values of around 1 ng rl in the open
regions, with higher values in the German Bight (due to the Elbe) and also in some
areas east of Scotland and in the Skagerrak, where values were between 1 and 10 ng rl.
The second winter survey resulted in a different distribution of Hg concentrations,
where most areas were below the detection limit of 0.5 ng rl, the bight was again
around 10 ng rl, but 10 stations east of Scotland showed values in excess of 200 ng rl.
The author speculated that there might be some connection between these high levels
and gas production.
The concentrations of elemental mercury HgO in surface waters from the ScheIdt
Estuary and the North Sea have been reported (Baeyens and Leermarkers 1998). As
with total mercury, a seasonal variation was noticed with concentrations of HgO reported to be 0.02-0.76 ng rl in winter and 0.48-0.13 ng I-I in summer. In the North
Sea, HgO concentrations ranged from 0.012 to 0.16 ng rl with the concentrations being higher in coastal stations. Positive correlation with phytoplankton concentration
was observed, and the possibility of the involvement of phytoplankton in the production of HgO was suggested. The authors stressed the need for studies on photocatalytic reduction of mercury species and on bacterial demethylation.
13.4.2
Mediterranean Sea
It was pointed out some years ago that many marine organisms living in the Mediterranean basin have higher mercury body burdens than do the same species living in
the Atlantic or other Oceans (Stoeppler et al. 1979; Bernhard 1985,1988; Renzoni et al.
1998). Using the measured concentrations of mercury in sardines from both the Mediterranean and Atlantic Ocean, Bernhard (1985) calculated the mercury levels in Mediterranean and Atlantic plankton, and then assuming that the mercury concentration
in plankton is 5 000 times that of sea water, he concluded that the Mediterranean should
contain 5 ng rl and the Atlantic 1 ng rl of mercury. Values for the mercury concentration in the Mediterranean have reported to be in the range 0.5-1.5 ng rl (May and
Stoeppler 1983; Kniewald et al. 1987; Dorten et al. 1991). The high levels of mercury
in Mediterranean biota have been discussed for many years. It has been pointed out
(Bernhard 1985; Renzoni et al. 1998) that about 55% of the world's mercury resources
are in the Mediterranean basin (an area about 1% of the total area of the planet),
and that the turnover of water through the straits of Gibraltar is low, thus Mediterranean biota have high levels of mercury from natural sources. Riverine inputs of Hg to
the Mediterranean Sea, from the Rhone, Ebro, Arno, Krka, Nile and Tiber have been
estimated to be relatively small and lower than previously suggested (Dorten et al.
1991).
13.4.3
The Pacific and Atlantic Oceans
The measurement of chemical species of mercury at low concentrations in the open
oceans has been made possible by recent improvements in analytical techniques (Gill
M.E. Farago
Port of Hamburg. Schmidt also reported values of mercury concentrations, in samples
from 10 m depth, carried out in two surveys of the entire North Sea in May/June 1986
and January/March 1987. The first survey showed values of around 1 ng rl in the open
regions, with higher values in the German Bight (due to the Elbe) and also in some
areas east of Scotland and in the Skagerrak, where values were between 1 and 10 ng rl.
The second winter survey resulted in a different distribution of Hg concentrations,
where most areas were below the detection limit of 0.5 ng rl, the bight was again
around 10 ng rl, but 10 stations east of Scotland showed values in excess of 200 ng rl.
The author speculated that there might be some connection between these high levels
and gas production.
The concentrations of elemental mercury HgO in surface waters from the ScheIdt
Estuary and the North Sea have been reported (Baeyens and Leermarkers 1998). As
with total mercury, a seasonal variation was noticed with concentrations of HgO reported to be 0.02-0.76 ng rl in winter and 0.48-0.13 ng I-I in summer. In the North
Sea, HgO concentrations ranged from 0.012 to 0.16 ng rl with the concentrations being higher in coastal stations. Positive correlation with phytoplankton concentration
was observed, and the possibility of the involvement of phytoplankton in the production of HgO was suggested. The authors stressed the need for studies on photocatalytic reduction of mercury species and on bacterial demethylation.
13.4.2
Mediterranean Sea
It was pointed out some years ago that many marine organisms living in the Mediterranean basin have higher mercury body burdens than do the same species living in
the Atlantic or other Oceans (Stoeppler et al. 1979; Bernhard 1985,1988; Renzoni et al.
1998). Using the measured concentrations of mercury in sardines from both the Mediterranean and Atlantic Ocean, Bernhard (1985) calculated the mercury levels in Mediterranean and Atlantic plankton, and then assuming that the mercury concentration
in plankton is 5 000 times that of sea water, he concluded that the Mediterranean should
contain 5 ng rl and the Atlantic 1 ng rl of mercury. Values for the mercury concentration in the Mediterranean have reported to be in the range 0.5-1.5 ng rl (May and
Stoeppler 1983; Kniewald et al. 1987; Dorten et al. 1991). The high levels of mercury
in Mediterranean biota have been discussed for many years. It has been pointed out
(Bernhard 1985; Renzoni et al. 1998) that about 55% of the world's mercury resources
are in the Mediterranean basin (an area about 1% of the total area of the planet),
and that the turnover of water through the straits of Gibraltar is low, thus Mediterranean biota have high levels of mercury from natural sources. Riverine inputs of Hg to
the Mediterranean Sea, from the Rhone, Ebro, Arno, Krka, Nile and Tiber have been
estimated to be relatively small and lower than previously suggested (Dorten et al.
1991).
13.4.3
The Pacific and Atlantic Oceans
The measurement of chemical species of mercury at low concentrations in the open
oceans has been made possible by recent improvements in analytical techniques (Gill