Distribution of Persistent Organic Pollutants and Mercury in Freshwater Ecosystems Under Changing Climate Conditions - Climate Change Impacts on Freshwater Ecosystems - page 191

60
30
0
K ow
Figure 8.6 Increment ratio from larvae to pupae of the concentrations of OCs and
PBDEs. The compounds are ranked by increasing K ow . The slashed line indicates the
average concentration increase for OCs (threefold) between the two metamorphic
stages. (Based on Bartrons et al . 2007.)
Once these compounds are introduced into the environment, temperature
becomes a determining factor in their distribution. Climatic changes imply a
change in temperature, and increases in temperature have been particularly high
in currently cold and mountainous regions. Hence, temperature variations should
result in a redistribution of contaminants accumulated in these areas. High-
mountain zones are inherently important: they represent the most remote
ecosystems present in Europe. Nonetheless, these zones are primary areas of
production of water resources for human use, constituting the headwaters of
river systems. Maintaining these zones in environmentally healthy conditions is
required for ensuring low levels of water contamination.
Studies on the atmospheric deposition of these compounds are important for
gaining knowledge of the processes associated with temperature dependence. These
have been performed in Izaña in Tenerife (van Drooge et al . 2001), Redon Lake in
the Pyrenees, Gossenköllesee in the Alps and Øvre Neadålsvatn in Norway (Carrera
et al . 2002). For all of these locations, greater deposition of these organic compounds
was observed during warm periods, which reflects a greater rate of volatilization
from the different environmental compartments in which they were stored (Carrera
et al . 2002). However, the retention capacity of the compounds is greater in cooler
lakes, and the least volatile compounds are the most retained (Fig. 8.7).
Another major factor is the general concentration of these compounds in the
atmosphere where temperature changes associated with climate change first
appear. Their seasonal concentration has been studied at Redon Lake, Skalnate
Pleso in the Tatra Mountains (van Drooge et al . 2004) and Izaña (van Drooge
et al . 2002). In general, the same POP distributions are found in all sites, which
confirms the capacity of these compounds for volatilization and their global
impact. The atmosphere acts as a store of these pollutants that are transferred to
continental freshwater ecosystems by precipitation. Warmer periods correlate
with greater volatilization (Fig. 8.8). This trend is clearest among the least volatile