Site-specific risk assessment and management of point and diffuse sources - Environmental Deterioration and Contamination: Problems and their Management - page 324

Remote sensing, GIS-based tools and other predictive methodologies support the
management of diffuse pollution, typically air and water pollution of diffuse origin or
disperse nature.

2.3 Characterization of point and diffuse pollution
Point and diffuse source pollution can be characterized based on the pollution gen-
eration scale, its extent and discharge intervals, pollution monitoring, control and
management approach, the scale of pollution impacts and the type of pollutants.

2.3.1 Characteristics of point sources
Point sources are defined as stationary locations or fixed facilities from which pol-
lutants are discharged into the environment. Point sources can be characterized as
follows:

- Pollution generation can be traced easily because it always comes from an

exactly identifiable single source and enters the environment through a discernible,
confined and discrete conveyance such as a smokestack, pipe, ditch, tunnel or
conduit;

- Point source discharges are usually continuous or regular depending on the type

of activity they are associated with;

- There is a gradient in the distribution of the pollution: it has highest concentrations

nearest the source and diminishing concentrations farther away from the source;

- Pollution transport in air depends on meteorological circumstances, air velocity

and direction;

- Pollution transport in water: higher flow rates in rivers induce lower concentra-

tions due to dilution of the effluent discharge;

- Transport from solid surfaces and soils: precipitation, subsurface runoff flow

rate and direction, as well as the topography together determine the transport
target;

- The impacts of pollution are generally obvious, both over the short and long term;

- Point sources can be monitored at the point of origin;

- Prevention and restriction, as well as treatment of the discharge before release are

equally effective and controllable methods for risk reduction;

- Point source pollution should be treated at the source of origin if possible;

- Air, water and soil quality impacts can be assessed at a local scale;

- The most important pollutants from point sources are transported according to

their chemical characteristics: volatile contaminants mainly enter the air, water-
soluble ones pollute surface or subsurface waters and the sorbable substances are
bound to the soil solid phase and move further by water or by solid transport;
◦ Point source air pollutants come from combustion and energy production;

◦

Water pollutants stem from discharges from the treatment of urban waste-
water, industry and fish farms;

◦ Soil pollutants come mainly from storage and transport facilities;