Environmental Engineering Reference
In-Depth Information
and processing works or could be deposited from aerial sources via smelting.
The proliferation of manufacturing industries in the twentieth century
increased the sources, types and forms of metals within the environment and
led to large-scale impacts within affected ecosystems (e.g., see Chapter 13 ).
Agriculture has also been a significant source of metals due to their presence
in many pesticides, herbicides and fertilisers (e.g., Nicholson et al. 2003 ;
Nziguheba & Smolders 2008 ). During the latter half of the twentieth century
increased environmental legislation together with a decline in manufacturing
within many countries led to a decrease in the occurrence of metalliferous
discharges (see, for example, Chapters 13 and 14 ); however, the legacy of these
previous activities continues to act as both diffuse and point sources to the
aquatic environment via drainage from mine workings and mobilisation of
contaminated floodplain sediments (e.g., Ullrich et al. 2007 ; Hutchinson &
Rothwell 2008 ; Tiefenthaler et al. 2008 ). Increasing urbanisation has also led
to the creation of different sources of metals including urban runoff due to
wear and tear of motor vehicles (e.g., Sansalone & Buchberger 1997), street
dust and tanker effluents (Brown and Peake 2006 ). More recently metals such as
silver and tin in the form of nanoparticles have been identified as a potential
source of contamination (see Chapter 5 ). These sources of metal contamination
are more difficult to control and pose a potential threat to ecosystems.
In addition, in areas of the world where legislation is less stringent the 'trad-
itional' sources of metals still act as significant contributors of pollutants to
the environment. For example, mercury has been shown to be a significant
contaminant in areas such as Latin America, Asia and Sub-Saharan Africa
particularly from gold mining (Ullrich et al. 2007 ; Marrugo-Negrete et al.
2008 ), and lead exposure is also a major problem in developing countries
with significant sources including metal smelters (Meyer et al. 2008 ).
In this chapter, we review the impacts of metal pollution on freshwater
macroinvertebrates, a key basal trophic component of the aquatic ecosystem.
This is a group of organisms often used in the monitoring of rivers and is a
major component of many national monitoring schemes such as that of the
Environment Agency in the UK (see Chapter 6 and Metcalf-Smith 1994 ). Macro-
invertebrates are also key organisms in the transfer of energy through trophic
levels and fluxes of matter within river systems, and therefore any effects of
metals are likely to be transferred and/or biomagnified through the food web
(Petersen et al. 1989 ; Maltby 1996 ; Barata et al. 2005 ). Within this chapter we
therefore aim to provide a review of the key chemical variables that affect
invertebrate communities within rivers receiving metalliferous discharges, the
importance of the source of the contaminant and the potential risks to the food
chain. We highlight the key research areas that need to be addressed, particu-
larly in light of recent developments within the relevant legislation, in order to
effectively manage these affected ecosystems in the future.
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