Climate Change and the European Water Dimension - Agri ...

and ice have quite a low capacity to store POPs, so that an important aspect of POP
cycling in these environments concerns the extent to which POPs in the snow/ice
pack may be re-emitted to atmosphere, or percolate to soils and water bodies,
particularly during snow melt (e.g., see Franz et al., 1997).
Influence of changing land use and surface cover
As shown in the previous section, the processes of deposition and re-emission are
key to the global cycling of POPs, so any underlying changes in land use, or surface
cover characteristics induced by climate change could have a potentially profound
effect on such cycles. Other aspects of land use, and the link to hydrological cycles
are also likely to be of importance. Examples include:
• Deforestation, and other changes to habitat type and distribution, especially
underlying effects on soil organic carbon budgets. It seems that the organic
matter-rich soils of the temperate northern hemisphere are particularly
important environmental reservoirs/sinks of POPs, for example (Meijer et al.,
2003b);
• Underlying changes to the hydrological cycle, such as flood frequency/
seasonality/ intensity. This could potentially impact POP cycling and
distribution through sediment mobilisation, and delivery to floodplains, for
example (Bergqvist et al., 2000).
• Both of the above examples could have an important effect by influencing the
regional patterns of chemical usage – for example through the distribution of
urban and agricultural areas, and the associated influence on the emissions
of industrial chemicals, and the use of agrochemicals.
The role of air mass origin
Changes in both temperature and large-scale wind systems are associated with
global atmospheric circulation patterns, while – as shown above - surface air
temperatures influence atmospheric concentrations of POPs. However, the link
between inter-annual changes in atmospheric POP concentrations and climate
variability (e.g. Shindell et al., 1999) has not been studied extensively. As Ma et al
(2004) suggest, this may be due to the lack of continuous atmospheric POP
measurements before the 1980s, and because any associations of climate
fluctuations with air concentrations of POPs are difficult to discern while current
(primary) emissions dominate annual cycles. However, utilising data obtained from
two major POP air monitoring programmes established in North America during the
1990s, - the Canadian Northern Contaminants Program (NCP), and the Integrated
Atmospheric Monitoring Network (IADN), Ma et al (2004) looked for evidence of
relationships between air concentrations of hexachlorobenzene (HCB), the HCHs
and PCBs between December 1990 and May 2000, and major Northern Hemisphere
climate variables. They concluded that: ‘Inter-annual variations of POP air
concentrations from the Great Lakes region and the Arctic have been strongly
associated with atmospheric low-frequency fluctuations, notably the North Atlantic
Oscillation (NAO), the El-Nino-Southern Oscillation (ENSO) and the Pacific North
American (PNA) pattern. This suggests interactions between climate variation and
the global distribution of POPs. Atmospheric concentrations of HCHs, HCB and
several lighter PCBs measured around the Great Lakes basin increased during the
positive phases of NAO and ENSO in the spring. This implies that anomalous high air
temperatures associated with NAO and ENSO enhance volatilisation of POPs from
reservoirs on the Earth’s surface accumulated in the past. These compounds are
then available to transport from source regions to more pristine regions such as the
Arctic under favourable flow patterns associated with global climate variations’.
213