Geoscience Reference
In-Depth Information
8
Distribution of Persistent Organic
Pollutants and Mercury in Freshwater
Ecosystems Under Changing Climate
Conditions
Joan O. Grimalt, Jordi Catalan, Pilar Fernandez,
Benjami Piña and John Munthe
Introduction
Persistent organic pollutants (POPs) and some trace metals (e.g. mercury, cadmium
and lead) are toxic substances released into the atmosphere by a range of urban,
industrial and agricultural processes. Once emitted into the atmosphere, these
pollutants are dispersed widely and are deposited onto waterbodies. They can
enter the food web where they bioaccumulate and become toxic to aquatic and
terrestrial organisms. Many of the diverse aspects of climate change (e.g.
temperature increase, variations in rainfall, wind patterns and dust deposition)
affect the distribution and mobility of toxic substances in freshwater systems.
Although many toxic substances introduced into the environment by human
activity have been banned or restricted in use, many persist, especially in soils and
sediments, and they either remain in contact with food webs or can be eventually
re-mobilized and taken up by aquatic biota (Catalan
et al
. 2004; Vives
et al
.
2005). The high levels of metals (e.g. Hg) and POPs (polychlorobiphenyls [PCBs],
DDE) in the tissue of freshwater fish in arctic and alpine lakes (Grimalt
et al
.
2001; Vives
et al
. 2004a) attest to the mobility and transport of these substances
in the atmosphere (Carrera
et al
. 2002; Fernandez
et al
. 2002, 2003; van Drooge
et al
. 2004) and their concentration in cold regions (Fernandez & Grimalt 2003).
The possible consequences of these factors on water quality are described below.
Organohalogen compounds
POPs are characterized by high chemical stability, which stems from their halogen
substituents: primarily chlorine, constituting the so-called organochlorine
compounds (OCs). OCs first appeared in the environment 70 years ago, but due
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