Distribution of Persistent Organic Pollutants and Mercury in Freshwater Ecosystems Under Changing Climate Conditions - Climate Change Impacts on Freshwater Ecosystems - page 196

Salmo trutta (liver) Daphnia pulicaria K ow

10 8
10 7
10 6
10 5
10 4
10 3
10 2
10 1
10 0

Figure 8.10 Comparison between ratios of lipid normalized PAHs in Salmo trutta
(liver), Daphnia pulicaria and water (dissolved phase) and the expected values from the
octanol-water partition coefficients of the compounds. Water concentrations in
Vilanova et al . (2001b) and Fernandez et al . (2005). Phe, phenanthrene; A, anthracene;
Fla, fluoranthene; Py, pyrene; B a A, benz[ a ]anthracene; Chr, chrysene; BFlas, benzo[ b + k ]
fluoranthenes; B a Py, benzo[ a ]pyrene; IndPy, indeno[1,2,3-cd]pyrene; BPer, benzo[ ghi ]
perylene; Dib ah A, dibenz[ a,h ]anthracene. (Based on Vives et al . 2005.)

additional improvements in combustion processes and through greater use of
solar and wind power. The future global environmental occurrence of these
compounds will depend on the balance between fossil fuel energy consumption
and improvement of combustion methods and the degree of replacement of
fossil fuel use by renewable sources. This area remains plagued with uncertainties.
The effects of future improvements in combustion technology on the total
amount of PAH generated may be offset by increased energy consumption.

Mercury and temperature
While mercury has many characteristics similar to the organic compounds
discussed above (e.g. semi volatility, persistence, toxicity), it differs in the
importance of the different forms of mercury existing in the environment. In air,
elemental mercury vapour is predominant while oxidized divalent compounds
are the most common in water, soils and sediments. In these media, methylmercury
generally accounts for a very small fraction (<1%) but since this species is the
most toxic form and one that is capable of bioaccumulation, it is the most
important from environmental and health perspectives.
Increased temperatures will change the environmental cycling of mercury
because the rates of transformation between chemical species (e.g. oxidation,
reduction, methylation) and the rates of transport between compartments (e.g.
exchange between air and surfaces or water and sediments) depend on this
variable. Very little is known about the overall impacts of temperature on mercury
cycling. In general, increased oxidation rates of atmospheric mercury would be
expected, which would involve increased deposition on land and water. This may