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and present the basis of environmental risk management of point and diffuse contam-
inant sources. We will consider that point source pollution is limited to a relatively
small area and diffuse source pollution may be dispersed in a watershed or across a
larger area.

2.1 Pollution sources
2.1.1 Definitions

Pollution is the accidental or deliberate release into the surrounding environment of
unwanted physical agents, chemical substances and biological materials (including
living organisms), as well as of energy in the form of heat, light, vibration and noise
from a source. Pollution is in particular the result of human activities, and contami-
nants in the environment may become part of global ecosystem processes. This means
that the excess material and energy become an integral part of the water and element
cycles and change the natural material and energy balances.
As a general term, a source is a point at which something springs into being or
from which something derives or is obtained such as the point of origin (spring) of a
brook or river.
Pollution sources in a broad sense have a complex meaning. The origin of the
pollution can be an activity producing or using chemical substances and products
(synthetic material production, mining, product transport and use in services and in
households). Material-emitting residential, recreational, industrial or agricultural land
uses themselves are sources of pollution. In a narrower sense, the pollution source is a
location, a point or an area of potential discharge into the environment.
Primary sources are those sources, wherefrom the pollutants have reached the
environment for first once emitted from production or from the use of the chemical
substances.
Secondary sources are the results of transport processes, moving/remobilizing
the contaminants from one place to another, even changing their physical or

chemical form.
Assuming a contaminant discharge point into air or water, the emitted gas, liquid
or solid is immediately carried away by the wind or water flow. Some contaminants
and transport routes keep the contaminant plume relatively concentrated, for example,
transport of solid contaminants by flood and their deposition in certain sedimentation
zones or floodplains. In other situations, for example, contaminants which tend to
be suspended, mixed or dissolved in gas or water load the environment diffusely by
deposition from air or transport by runoff waters over long distances. These types
of contaminants may originate from more primary and/or secondary sources and
aggregate by air, water or solid flows, according to the transport pathways. As a
result they may disperse across large areas, typically at watershed scale, where the
surface water system is the main transport route or in areas exposed to airborne
pollution.
Polluting substances can include materials which disrupt normal processes in
healthy ecosystems (Kaly, 2004) and humans. Polluting substances may occur in solid,
liquid or gaseous form. Some of the major substances that may cause pollution in
the environment are nutrients, hydrocarbons, persistent organic pollutants, pesti-
cides, heavy metals or pathogenic microorganisms, plants or animals. Humans are