Geography Reference
In-Depth Information
Table 11.5
Pesticides on list I (Black List) of the EC
Dangerous Substances Directive (76/464/ EEC).
one that occurred at the Chernobyl nuclear power
station in April 1986, which released 2× 10
18
Bq
of radioactive materials into the atmosphere and
subsequently led to contamination of freshwaters
and fluvial sediments with radio-caesium over
wide areas of Europe and beyond (e.g. Walling
et al
.
1992).
Sediment transport in rivers, especially in
suspended form, may also cause serious water
quality problems (Walling 1988). Accelerated soil
degradation and loss from agricultural land has
led to increased sediment yields in many river
systems (Walling 1995), which often result in
both 'in-stream' and 'off-stream' effects (Clark
et
al
. 1985; Tim and Jolly 1994). The former include
biological impacts through for example
infiltration of fine sediment into spawning
gravels, recreational impacts leading to
restrictions on swimming, boating and fishing,
sedimentation impacts, which cause reduction in
reservoir capacity and navigation problems,
abrasion impacts relating to damage of HEP
turbines, and aesthetic impacts through
degradation in the visual quality of the river
environment. The latter involve flood damage
when flood water cannot pass silted and aggraded
river channels, sedimentation problems in
irrigation and drainage channels, increased water
treatment costs because more time is required to
clarify turbid waters, and problems for the
industrial use of river water because sediment-
laden flows are less efficient for cooling and lead
to abrasion of plant. In addition to the physical
effects of turbid water, many chemical
contaminants are adsorbed by the silt and clay
fraction of river sediments and are transported
through the fluvial system in particulate-
associated form.
control the use of most organochlorine
compounds, such as DDT, because of their
toxicity and environmental persistence. Eight
pesticides are included in List I (Black List) of
the EC Dangerous Substances Directive (76/
464/EEC), and although the use of six of these is
no longer approved in the UK (Table 11.5), long-
term monitoring of river sites in England and
Wales demonstrates that older chemicals, such as
the insecticide dieldrin, are very persistent in the
fluvial environment (Environment Agency
1997a).
Other pollutants
A range of other pollutants may also cause water
quality problems. These include heated effluents,
especially from power generation facilities
(Langford 1990), and oil spills, such as the accident
on the Monongahela River, Pennsylvania, USA,
which resulted in the release of 3.5 million litres
of diesel fuel from a riverside tank in January 1988
and caused major disruption to water supplies,
factory closures, cessation of river traffic and high
wildlife mortality (Mason 1991). Radio-activity
may be added to freshwaters by cooling waters and
other effluents from nuclear power stations and
reprocessing facilities, and there is concern about
future contamination by leakage from land
disposal sites and in connection with
decommissioning of redundant nuclear plants. A
much greater threat of pollution by radioactivity
is associated with nuclear accidents, such as the
PATTERNS, TRENDS, PROTECTION
AND REMEDIATION—THE EXAMPLE
OF ENGLAND AND WALES
Data collected by the Environment Agency of
England and Wales and the statutory bodies that
preceded its formation provide information for a
