Geoscience Reference
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shown in Fig. 8.9 where it is plotted against the temperature gradient and compared
with the total PCB content in muscle of the same animals. The graphs show a linear
correlation between the logarithmic transformations of both series of data and the
reciprocal of absolute temperatures. These trends suggest that Cyp1A induction in
mountain lake trout is related to PCB exposure, more specifically to penta- and
hexa-chlorobiphenyls, according to their physico-chemical properties. Likely
candidates are coplanar PCB congeners, such as PCB126, although other long-
transported pollutants could also be relevant for this effect. The strong dependence
of hepatic Cyp1A expression in trout liver along temperature gradients suggests that
POP redistribution as predicted by global warming projections may have significant
effects on the physiology of the exposed fish populations even at remote sites.
Polycyclic aromatic hydrocarbons and temperature
A study of the concentrations of PAHs in the livers of high-mountain lake fish
did not reveal any dependence on temperature (Vives
et al
. 2004b). This can
be explained by the lack of bioaccumulation of PAHs in fish and because the
global transport mechanisms of PAHs differ from those of organochlorine
pollutants. The distribution of PAHs in remote (Fernandez
et al
. 2002) and
urban (Aceves & Grimalt 1993) zones occurs in association with particles,
especially soot. Thus, the concentrations of these compounds are more
reflective of local sources than OCs.
Most organisms exhibit PAH distributions largely dominated by phenanthrene,
in accordance with its predominance in atmospheric deposition, water and suspended
particles (Vives
et al
. 2005). Total PAH levels are higher in organisms from littoral
habitats than from the deep sediments or the pelagic water column. However,
organisms from deep sediments exhibit higher proportions of higher molecular
weight PAH than those in other lake areas. Different organisms exhibit species-
specific features in their relative PAH composition that point to different capacities
for uptake and metabolic degradation. Brown trout show an increased capacity for
metabolic degradation since they have lower PAH concentrations than in their food
and they are strongly enriched in lower molecular weight compounds (Fig. 8.10).
The PAH levels in trout depend greatly on prey living in the littoral areas.
The atmospheric concentrations of PAHs tend to be higher in winter, when
more fuel is consumed, than in summer (Aceves & Grimalt 1993; Fernandez
et al
. 2002). Increasing use of air conditioners may lead to a reversal of this trend
in the future because increasing energy consumption means higher PAH emission.
This would imply a higher proportion of PAHs in the gas phase than in association
with particles compared with the present phase distribution, particularly in cities
(Aceves & Grimalt 1993).
In any case, based on the gradual rise in the use of energy - 85% of which
comes from burning of fossil fuels - increased concentrations of these compounds
can be predicted for the future. However, the concentrations of PAHs
in high-mountain lakes decreased by 30% from the 1970s to the present
(Fernandez
et al
. 2000). This decrease is due to improvements in combustion
processes, primarily at power stations, leading to a lower emission of pollutants.
The emission of these carcinogenic hydrocarbons can be further limited through
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