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PeCB+HCB (PP)
Sum PCBs (PP)
Sum DDTs (PP)
Sum HCHs (PP)
PeCB+HCB (DP)
Sum PCBs (DP)
Sum DDT (DP)
Sum HCHs (DP)
Flow river
Suspended particulate matter
(SPM)
PP - Particulate phase
DP - Dissolved phase
Figure 8.12
Concentrations of suspended particulate matter and pentachlorobenzene
(PeCB), HCB, PCBs, HCHs and DDTs plotted against river flow for the Ebre River. As
observed, the concentrations of these compounds increase with increasing flow and
with higher levels of suspended particles. This trend reflects the mobilization of
contaminated material located in the Flix reservoir due to increased river flow. DP,
dissolved phase; PP, particulate phase. SPM: black thick line. River flow: blue thick line.
the relative increase in methylmercury was larger than the relative increase in water
transport. Increased soil wetness therefore enhanced methylmercury formation.
Concurrent increases of dissolved organic carbon and sulphide in run-off water
suggested that soil was saturated with water and that anaerobic conditions had been
established, favouring mercury methylation via sulphate-reducing micro-organisms.
The results of these experiments are consistent with the scenario mentioned above,
indicating that future climate change may lead to increased loadings of methylmercury
to aquatic ecosystems in areas where increased precipitation is expected.
Anthropogenic effects associated with water management
Apart from the effects that are most directly linked to climate change, there is a
second group of factors that can influence the quality of water resources. These can
be defined as negative collateral effects derived from new water management
strategies used by humans to address scarce water supplies. As these causes are
indirect, their influence is much more difficult to ascertain. For example, climate
change can lead to changes in land use, forcing farmers to adapt agricultural practices
(e.g. changing tilling methods, extending production seasons, modifying irrigation
plans and confronting new pests). These new practices can have major consequences
on the types of pesticides used, which in turn can ultimately influence the quality of
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