Nonpoint discharges

The principal inputs can be divided into two broad categories point sources and nonpoint sources. The point inputs are considered to luive a well-defined point of discharge, wliicli under most circumstances is continuous. A... 

For an aquatic model of chemical fate and transport, the input loadings associated with both point and nonpoint sources must be considered. Point loads from industrial or municipal discharges can show significant daily, weekly, or seasonal fluctuations. Nonpoint loads determined either from data or nonpoint loading models are so highly variable that significant errors are likely. In all these cases, errors in input to a model (in conjunction with output errors, discussed below) must be considered in order to provide a valid assessment of model capabilities through the validation process. 

Pesticides in wastewaters come typically from point sources of contamination such as disposal sites and landfills where industrial or agricultural wastes are buried without any consideration, as well as discharges from industrial effluents from pesticide production plants. Furthermore, nonpoint sources derived from regular agricultural activities, especially in intensive agricultural areas, and accidental spills can also be significant. Urban use of pesticides is also possible in large cities where the use of herbicides and insecticides may result in runoff into the sewers. These sewers in turn may expel pesticides into wastewater treatment plants (WWTPs). 

Hexane is probably released to water from a number of sources including industrial discharges, effluents from municipal waste-treatment plants, and nonpoint-source runoff from roads and other surfaces. Insufficient information is available to quantify the releases in a comprehensive fashion. 

There are numerous sources that release cyanide into water. Cyanide is released into water from both point and nonpoint sources. The major point sources of cyanide released to water are discharges from publicly owned treatment works (POTWs), iron and steel production, and organic chemical industries (Fiksel et al. 1981). Estimates based on data from the mid-to-late 1970s indicate that these sources account for 89% of the estimated 31 million pounds of total cyanide discharged annually to surface... 

Diazinon is released into water directly from point source discharges, from drift during pesticide applications, and from nonpoint source runoff from agricultural and urban areas. Since diazinon is not a Priority Pollutant under the Clean Water Act, it has not been evaluated extensively in water quality... 

Herbicides derived from point and nonpoint sources can be transported to streams by runoff from agricultural and urban areas, discharge from reservoirs and aquifers, and precipitation. The physiochemical properties of the triazine herbicides, as well as other factors such as usage, precipitation patterns, and farming practices, are important in determining the amounts and concentrations of these chemicals in streams. 

The Clean Water Act focuses on improving the water quality of the nation. It provides for establishment of standards, development of technical tools, and financial assistance to address the causes of pollution and poor water quality, including municipal and industrial wastewater discharges, nonpoint source runoff pollution... 

Transport and fate of pollutants also depends upon the source of pollutants. Contaminants that originate from a definable source, for example, a smokestack or effluent (wastewater discharge) pipe, are known as point sources . Sometimes, however, the source of the pollutant is more diffuse for example, when pesticides are carried by runoff from a large area into a river. These sources are called nonpoint sources . Often, point and nonpoint sources may be combined or interconverted for example, if nonpoint runoff from a city is channeled into a discharge pipe via storm sewers. 

Sources of pollutants are commonly divided into two categories point sources and nonpoint sources. Point sources refer to discrete, localized, and often readily measurable discharges of chemicals. Examples of point sources are industrial outfall pipes, untreated storm water discharge pipes, and treated... 

The Water Quality Act of 1987 strengthened federal water quality regulations, regulated toxic discharges, expanded treatment to nonpoint sources, and established new stormwater restrictions. 

The two major categories of discharges into surface waters are point sources, which are essentially any discharge that can be specifically located by finding the discharge pipe, and nonpoint sources. A few examples of point sources include ... 

Industrial discharges Municipal wastewater discharges Municipal storm water discharges A few examples of nonpoint sources include ... 

The more difficult category of discharge source to regulate is the nonpoint source. This source of discharge covers a wide and varying area and a sample cannot be taken that is truly representative of a specific location. Thus, there are numerous variables that could impact the discharge sample that limits the enforcement of a set of discharge standards for this type of source. 

The principal nonpoint sources are agricultural, silviculture, atmospheric, urban and suburban runoff, and groundwater. In each case, the distinguishing feature of the nonpoint source is that the origin of the discharge is diffuse. That is, it is not possible to relate the discharge to a specific well-defined location. 

Prior to 1972, water quality regulations were limited to point sources. A point source is a single source, such as a commercial facility or municipal wastewater treatment, that discharges effluent directly into a waterway. With the CWA, water quality was expanded to encompass nonpoint sources. Nonpoint sources often associated with waste from runoff (agricultural, mine tailings, etc.) are those contaminant sources whose origin cannot be identified. 

This information exchange provides responses to inquiries pertaining to management of nonpoint sources of water pollution and EPA s programs which are in place to control these discharges. In addition, a bulletin board system (NPS BBS) provides a means to exchange text and program computer files as well as provide a forum for open discussion. 

It is also used as an electron acceptor by microorganisms. Nitrihcation of ammonia N in soil is a source of nitrate. In addition, nonpoint and point source discharges from terrestrial ecosystems can be a major source of nitrate to wetlands and aquatic systems. In the atmosphere, nitrogen oxides can react with photochemically produced free radicals and produce nitric acid, which contributes to acid rain. Nitrate is also a common fertilizer used in agricultural ecosystems. 

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