Distribution of Persistent Organic Pollutants and Mercury in Freshwater Ecosystems Under Changing Climate Conditions - Climate Change Impacts on Freshwater Ecosystems - page 200

water that enters rivers or phreatic waters. Minimizing the impact of contaminants
in water will require a major effort to control pollution by pesticides and other toxic
pollutants.
Conclusions
Volatile heavy metals and POPs present much more cryptic problems than those of
habitat change, acidification or eutrophication. Their effects on communities are
largely unknown and difficult to trace, because they are generally sub-lethal. Health
implications for fish and their human consumers are nonetheless clear and the
volatility and condensation effects make it very likely that a warmer climate in
particular will increase their transfer to polar and mountain regions. One of the
more poignant observations of recent years has been that of the widespread
contamination even of Antarctic ecosystems with these substances (Bargagli 2008).
However, in the areas closer to emission sites, warmer temperatures may result
in higher concentrations of these compounds in air than at present. This change
will increase the dispersion capacity of hydrophobic organic pollutants and
mercury, leading to higher rates of toxification of humans and higher organisms
through respiration. This effect will also be important for PAHs although in this
case the ultimate environmental impact will depend on the balance between
improved combustion sources and future energy demands, which may increase
following population and wealth growth.
The implications of increased temperatures will be similar for mercury.
Transformation into methylmercury may be enhanced at higher temperatures
due to increased microbial activity. Higher temperatures in Arctic and northern
environments, where cold conditions currently limit methylation and mercury
mobility, are of concern. In Scandinavia, thousands of lakes have fish with
mercury levels above the health guidelines. The projected decreases in atmospheric
precipitation, e.g. rain and snow may further increase these levels due to higher
proportions of groundwater percolating through mercury-rich soils.
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