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Measurements of dissolved methane are useful in recognizing environments where all three CFCs can be degraded.
Measurements of dissolved nitrogen and argon can be used to help determine recharge temperature and excess air and to recognize environments undergoing denitrification.
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.
CFCs have been increasingly used in oceanic studies since the late 1970s as tracers of oceanic circulation, ventilation, and mixing processes.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. Because of the effect of these factors on CFC concentration, collection of additional data is often needed to determine the apparent age of ground water. For example, measurements of concentrations of dissolved gases, such as dissolved oxygen, help to define the potential for microbial degradation.
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.