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CFCs also can be used to trace seepage from rivers into ground-water systems, provide diagnostic tools for detection and early warning of leakage from landfills and septic tanks, and to assess susceptibility of water-supply wells to contamination from near-surface sources.
During the past 50 years, human activities have released an array of chemical and isotopic substances to the atmosphere.
Concentrations of CFC-11, CFC-12, and CFC-113 in water recharged in equilibrium with air between the years 19 at temperatures of 5 to 25C.
The CFC analysis determined that concentrations of CFC-11, CFC-12 and CFC-113 were 493, 203, and 28 pg/kg in the water sample to be dated. B., Busenberg, Eurybiades, Drenkard, Stefan, Schlosser, Peter, and Michel, R. N., Busenberg, Eurybiades, Drenkard, Stefan, Schlosser, Peter, Mc Connell, J. L., Ekwurzel, Brenda, and Weppernig, Ralf, 1998b, Flow of river water into a karstic limestone aquifer, 2.
Production of CFCs ceased in the United States as of January 1, 1996, under the Clean Air Act. M., ed., Regional Ground-water Quality: Van Nostrand Reinhold, p.
Current estimates of the atmospheric lifetimes of CFC-11, CFC-12, and CFC-113 are about 45, 87, and 100 years, respectively.
However, shallow ground-water supplies are generally young (recently recharged) and, because there has been a wide variety of man-made pollutants produced in the 20th century, are more susceptible to contamination than deeper ground water.
CFC-113 has been used primarily by the electronics industry in semiconductor chip manufacturing, in vapor degreasing and cold immersion cleaning of microelectronic components, and surface cleaning.
Probably better known to the public as Freon, CFCs are nontoxic, nonflammable and noncarcinogenic, but they contribute to ozone depletion. J., and Busenberg, Eurybiades 1994, Estimation and corroboration of shallow ground-water flow paths and travel times by environmental tracer and hydraulic analyses A case study near Locust Grove, Maryland: Water Resources Research, v.
Chlorofluorocarbons are stable, synthetic organic compounds that were developed in the early 1930s as safe alternatives to ammonia and sulfur dioxide in refrigeration and have been used in a wide range of industrial and refrigerant applications. N., Busenberg, Eurybiades, Drenkard, Stefan, and Schlosser, Peter, 1996, Age-dating of shallow groundwater with chlorofluorocarbons, tritium/helium 3, and flow path analysis, southern New Jersey coastal plain: Water Resources Research, v.
Production of CFC-12 (dichlorodifluoromethane, CF). CFC-11 and CFC-12 were used as coolants in air conditioning and refrigeration, blowing agents in foams, insulation, and packing materials, propellants in aerosol cans, and as solvents.