Water releases nonpoint sources

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... 

All point source and nonpoint source wastewaters at an industrial site must be properly managed for source separation, waste minimization, volume reduction, collection, pretreatment, and/or complete end-of-pipe treatment [39,47]. When industrial waste is not disposed of properly, hazardous substances may contaminate a nearby surface water (river, lake, sea, or ocean) and/or groundwater. Any hazardous substance release, either intentionally or unintentionally, increases the risk of water supply contamination and human disease. Major waterborne contaminants and their health effects are listed below. 

Cresols are widely distributed natural compounds. As discussed above, they are formed as metabolites of microbial activity and are excreted in the urine of mammals (Fiege and Bayer 1987) and humans (Needham et al. 1984). Cresols from human urine are probably biodegraded at municipal sewage treatment facilities prior to release to ambient waters. However, for combined septic and storm sewage systems, cresols may be released to surface waters during periods of precipitation when influent volumes exceed treatment plant capacities. Also, in rural and suburban areas where septic tanks are used (o- and m-cresols can resist anaerobic digestion), human excrement may be a nonpoint source release of cresols to groundwater. 

Point sources are mainly responsible for the pollution of surface waters (rivers, lakes, seas), whereas nonpoint sources mainly contribute to the pollution of groundwater resources. Moreover, releases from point sources can be treated by wastewater treatment plants, whereas nonpoint source releases can only be minimized. 

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... 

Diazinon released to water from both point and nonpoint sources may be emitted to the atmosphere by volatilization, sorbed to soils and sediments, or accumulated in aquatic organisms. While evaporation may not be expected to be significant based upon the Henry s law constant (see Table 3-2), volatilization of diazinon can be an important transport process. Sanders and Seiber (1983) reported that 17% of the diazinon added to a model pond volatilized in 24 hours. Diazinon released to water also may be adsorbed moderately by soils and sediments based on its organic carbon partition coefficient (K00) values measured in soil (Sharom et al. 1980a). Because this pesticide is only moderately adsorbed by some soils, leaching into groundwater can occur. 

PAHs enter the environment from both natural and man-made sources, and the anthropogenic point and nonpoint sources are the major sources. The nonpoint sources are diffuse sources disseminated through the air and waterways. In aquatic systems, PAH-enriched particles or floes may settle to the lake s bottom under calm conditions and accumulate in the sediments. Once the PAH-enriched particles have accumulated in the lake s floor, they may undergo a number of changes that are mediated by chemical or microbial activities. As a result, the bound PAHs can be released from the sediment into the water phase. Once they enter the water column, they may also enter phytoplankton. The PAHs in phytoplankton may then bioaccumulate in the food web. This can cause both acute and chronic effects in fish, birds and other mammals that feed on aquatic organisms (Zhang, 1998). 

Though the quantities of each that are released vary with farming practices and animals or crops raised, they are the most important nonpoint source of water pollution. 

Progress has been made in some areas since 1970. Emissions of pollutants from point sources into air and water have decreased. Toxic releases are decreasing. Some Superfund sites have been cleaned up. Businesses would no longer think of dumping a barrel of waste solvent on the ground at the landfill site so that the barrel could be used again for the same purpose. Control of pollutants from nonpoint sources is still a problem. There is now more international cooperation and discussion of global problems, such as ozone depletion by chlorofluorocarbons and the effect of... 

Predicting the environmental fate and movement of plasticizers is currently hampered by a lack of information. There is also a lack of monitoring data to assess nonpoint sources. The aqueous solubility - a fundamental environmental property - of two of the 23 plasticizers has not been determined. As noted in this chapter, many properties such as Henry s Law constants, vapor pressure, organic carbon-water partition coefficients, octanol-water partition coefficients, bioconcentration factors, and photooxidation rates in the atmosphere were estimated using stractural analog models, empirical relationships based on other chemicals. Both biodegradation and adsorption appear to be the major mechanisms that control the fate of plasticizers released into the environment. Despite the... 

Sources of pollutants are commonly divided into two categories point sources and nonpoint sources. Point sources of pollution refer to discrete, localized, and often readily measurable discharges of chemicals. Examples of point sources are industrial outfall pipes, treated sewage outfalls from wastewater treatment plants, and untreated storm water discharge pipes. A spill of chemicals, due fo an accident on or near a surface water body, can also be regarded as a point source because its initial areal extent is limited. Point sources are often modeled by "plume" or "cloud" models that explicitly consider where and when a chemical release occurs, and then mathematically model the concentration of the chemical as a function of time and location. 

One way that contaminants are retained in the subsurface is in the form of a dissolved fraction in the subsurface aqueous solution. As described in Chapter 1, the subsurface aqueous phase includes retained water, near the solid surface, and free water. If the retained water has an apparently static character, the subsurface free water is in a continuous feedback system with any incoming source of water. The amount and composition of incoming water are controlled by natural or human-induced factors. Contaminants may reach the subsurface liquid phase directly from a polluted gaseous phase, from point and nonpoint contamination sources on the land surface, from already polluted groundwater, or from the release of toxic compounds adsorbed on suspended particles. Moreover, disposal of an aqueous liquid that contains an amount of contaminant greater than its solubility in water may lead to the formation of a type of emulsion containing very small droplets. Under such conditions, one must deal with apparent solubility, which is greater than handbook contaminant solubility values. 

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