Environmental Engineering Reference
In-Depth Information
boat harbors, high TBT and TPT concentrations were restricted to the top and
decreased significantly below (Fig. 3). In 1994, TBT surface concentrations
were up to 290 ng g
-1
,whichisabout5-10 times lower than in 1989 demon-
strating the effect of regulation. The decrease continues with time. Similar
TBT levels of 500-2500
gkg
-1
(dry weight) were found in harbor sediments
of other lakes, and river systems. The data lead to the conclusion that legis-
lation resulted in a marked reduction in boat harbor waters and sedimentary
input, but trace levels persist in surface waters, probably also due to inputs via
wastewater [19, 50].
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4.3
Biota
Contamination of marine and freshwaters with butyltins has spread all over
the world as evidenced by their detection in a wide range of oceans, environ-
mental media and particularly biota [4, 73-75, 87, 109]. Organisms serve as
important tools for assessing pollution. Biota tend to give a better indication
of contamination then water samples, because they integrate the pollution
situation over a longer period of time. Considerable butyltin and phenyltin,
but also methyltin compounds were found in marine and freshwater organ-
isms on a global scale. This holds true in particular for TBT and TPT showing
bioaccumulation in biota including mussels [63, 82, 110, 111], fish [14, 15] and
marine mammals [57, 90]. Because of the filter-feeding behavior and the gen-
erally high potential for bioaccumulation, bivalves have been widely used
as sentinel organisms for monitoring [76, 87]. Common molluscs including
Littorina littorea
and
Mya arenaria
,
Mytilus edulis
[111], but also oysters
may serve as bioindicators of TBT pollution in marine ecosystems, due to
the limited ability for metabolism and elimination. In a study, sampling 13
species of squids at 77 stations in the world oceans, highest TBT and TPT lev-
els of 279 and 519 ng g
-1
, respectively, were found in squid livers in coastal
areas. They were lower than in the open oceans. TBT concentrations were
higher in the northern hemisphere than in the southern, where TPT was not
detected [77]. Often, imposex in marine gastropods have been assessed in
conjunction with residues analysis, demonstrating a correlation between TBT
and TPT exposure and severity of imposex, for instance in the Lagoon of
Venice, Italy [112].
Whereas previous data were obtained from Canada, USA and Europe,
currently more data are reported from Japan and developing Asian coun-
tries. Although concentrations are generally low in mussels from coastal areas
of developing countries, higher levels were found at locations with inten-
sive maritime activities or aquaculture. Decreased levels of butyltins were
found in fish [85] and marine mammals [90] collected from coastal waters
in developing Asian rather than in industrialized countries such as Japan,
Europe and the USA. Contamination was always related to intensive maritime
