Contamination is considered every damaging change produced physically, quimically and biologically speaking within life resources, that is to say, air, land and water.
Contamination is the presence of a minor and unwanted constituent in another material, metal, chemical or mixture, often at the trace level. In chemistry, the term usually describes a single chemical, but inspecialized fields the term can also mean chemical mixtures, even up to the level of cellular materials.
Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans, groundwater).
Water pollution affects plants and organisms living in these bodies of water; and, in almost all cases the effect is damaging either to individual species and populations, but alsoto the natural biological communities.
Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds.
Water pollution categories
Surface water and groundwater have often been studied and managed as separate resources, although they are interrelated. Sources of surface water pollution are generallygrouped into two categories based on their origin.
Point source pollution refers to contaminants that enter a waterway through a discrete conveyance, such as a pipe or ditch. Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city storm drain. The U.S. Clean Water Act (CWA) defines point source for regulatory enforcement purposes. The CWAdefinition of point source was amended in 1987 to include municipal storm sewer systems, as well as industrial stormwater, such as from construction sites.
Non-point source pollution
Non-point source (NPS) pollution refers to diffuse contamination that does not originate from a single discrete source. NPS pollution is often the cumulative effect of small amounts of contaminants gathered from alarge area. The leaching out of nitrogen compounds from agricultural land which has been fertilized is a typical example. Nutrient runoff in stormwater from "sheet flow" over an agricultural field or a forest are also cited as examples of NPS pollution.
Contaminated storm water washed off of parking lots, roads and highways, called urban runoff, is sometimes included under the category of NPSpollution. However, this runoff is typically channeled into storm drain systems and discharged through pipes to local surface waters, and is a point source. However where such water is not channeled and drains directly to ground it is a non-point source.
Causes of water pollution
The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physicalor sensory changes such as elevated temperature and discoloration. While many of the chemicals and substances that are regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the concentration is often the key in determining what is a natural component of water, and what is a contaminant.
Oxygen-depleting substances may be natural materials, such as plant matter (e.g.leaves and grass) as well as man-made chemicals. Other natural and anthropogenic substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the gills of some fish species.
Many of the chemical substances are toxic. Pathogens can produce waterborne diseases in either human or animal hosts. Alteration of water's physical chemistry includes acidity (change inpH), electrical conductivity, temperature, and eutrophication. Eutrophication is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases in the primary productivity of the ecosystem. Depending on the degree of eutrophication, subsequent negative environmental effects such as anoxia (oxygen depletion) and severe reductions in water quality may occur,...