Digital Signal Processing Reference
In-Depth Information
nuisance substances to severe ecological impacts involving fish, birds and mammals, and on human
health.
The main characteristics of non-point sources include
:
they originate over a broad area (this makes
them difficult to identify or to assess), they respond to hydrological conditions, are not easily
measured or controlled directly (and therefore are difficult to regulate), and they are very much
dependant on land and related management practices. Agriculture is only one of a variety of causes of
non-point sources of pollution; however it is generally regarded as the largest contributor of pollutants
of all the categories.
Figure (2-3)
illustrates the range and relative complexity of agricultural non-point
source pollution is illustrated in.
Table (2-1)
outlines generally the classes of non-point sources and
their relative contributions to pollution loadings.
Figure (2-3): Hierarchical complexity of agriculturally-related water quality problems (Rickert, 1993)
Table (2-1): Classes of non-point sources and their associated pollutants
Non-point source
Definition
Associated pollutants
Agriculture
Animal
feedlots
Irrigation
Cultivation
Pastures
Dairy
farming
Orchards
Aquaculture
Runoff from all categories of agriculture leading to surface
and groundwater pollution. In northern climates, runoff from
frozen ground is a major problem, especially where manure
is spread during the winter. Vegetable handling, especially
washing in polluted surface waters in many developing
countries, leads to contamination of food supplies. Growth of
aquaculture is becoming a major polluting activity in many
countries. Irrigation return flows carry salts, nutrients and
pesticides. Tile drainage rapidly carries leachates such as
nitrogen to surface waters.
Phosphorus, nitrogen, metals,
pathogens, sediment,
pesticides, salt, BOD1, trace
elements (e.g. selenium).
Forestry
Increased runoff from disturbed land. Most damaging is
forest clearing for urbanization.
Sediment, pesticides.
Liquid waste
disposal
Disposal of liquid wastes from municipal wastewater
effluents, sewage sludge, industrial effluents and sludges,
wastewater from home septic systems; especially disposal on
agricultural land, and legal or illegal dumping in
watercourses.
Pathogens, metals, organic
compounds.
Urban areas
Residential
Commercial
Industrial
Urban runoff from roofs, streets, parking lots, etc. leading to
overloading of sewage plants from combined sewers, or
polluted runoff routed directly to receiving waters; local
industries and businesses may discharge wastes to street
gutters and storm drains; street cleaning; road salting
contributes to surface and groundwater pollution.
Fertilizers, greases and oils,
faecal matter and pathogens,
organic contaminants (e.g.
PAHs Polycyclic Aromatic
Hydrocarbons and PCBs
Polycyclic CHL-aorinated Bi-
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