Groundwater age dating with chlorofluorocarbons

How is groundwater dating with cfc-11/cfc-12 and CFC 113 possible?

Groundwater dating with CFC-11, CFC-12 and CFC-113 is possible because (1) the atmospheric mixing ratios of these compounds are known and/or have been reconstructed from 1940 to the present, (2) the Henrys law solubilities in water are known, and (3) concentrations in air and young water are relatively high and can be measured.

How do environmental processes affect the age of chlorofluorocarbons?

Many processes occur during recharge and in the groundwater environment that can affect CFC concentrations beyond those set by air-water equilibrium, and consequently affect interpretation of apparent age. Table 2 lists the most important processes, their effect on apparent CFC age, and relative importance.

Are chlorofluorocarbons time-dependent tracers in the ocean?

Bullister J.L. (1984) Atmospheric chlorofluomethanes as tracers of ocean circulation and mixing: Studies in the Greenland and Norwegian seas. Ph.D. Dissertation, University of Califorina, San Diego, La Jolla, 172pp. Bullister J.L. (1989) Chlorofluorocarbons as time-dependent tracers in the ocean. Oceanography 2, 12-17.

Are chlorofluorocarbons a tracer of groundwater transport processes?

Cook P.G., Solomon D.K., Plummer L.N., Busenberg E. and Schiff S.L. (1995) Chlorofluorocarbons as tracers of groundwater transport processes in a shallow, silty sand aquifer. Water Resour. Res. 31 (3), 425-434.

How can we date groundwater using CFC-12 and SF6?

Hence, due to the exponential nature of groundwater mixing it may be possible to date groundwater up to 100 years old using CFC-12 and SF 6, provided certain simplifying assumptions are fulfilled (e.g., steady state conditions and simple aquifer geometry).

Does CFC-113 contribute to groundwater pollution?

There are several documented cases of gross contamination of groundwater with CFC-113 (Jackson et al., 1992), particularly at some electronics plants in the USA. CFC-11 and CFC-12 are gases at ordinary temperatures (boiling points -23.6 and -29.8°C, respectively), and therefore will normally volatise when released.

How is groundwater dating with CFCs based on Henrys Law?

Groundwater dating with CFCs is based on Henrys law solubility. That is, the concentration of the gas dissolved in water in equilibrium with air is proportional to the partial pressure, p i, of the gas in air.

Where do we get CFC-12 and 3 h from?

River water seepage was shown to be the sole source of CFC-12 and 3 H to the Upper Floridan aquifer, and could be traced some 25 km south-east of the sinkholes in the direction of regional groundwater flow. The fraction of river water in the groundwater mixtures was determined from stable isotope and dissolved chloride data.

Can chlorofluorocarbons be used as hydrologic Tracer and age-dating tools?

Busenberg E. and Plummer L.N. (1992) Use of chlorofluorocarbons (CCl 3 F and CCl 2 F 2) as hydrologic tracers and age-dating tools: The alluvium and terrace system of Central Oklahoma. Water Resour. Res. 28 (9), 2257-2283.

What are CFCs (chlorofluorocarbons)?

Chlorofluorocarbons (CFCs) are stable, synthetic, halogenated alkanes, developed in the early 1930s as safe alternatives to ammonia and sulphur dioxide in refrigeration. Production of CFC-12 (dichlorodifluoromethane, CF2Cl2) began in 1931 followed by CFC-11 (trichlorofluoromethane) in 1936.

Are chlorofluorocarbons time-dependent tracers in the ocean?

Bullister J.L. (1984) Atmospheric chlorofluomethanes as tracers of ocean circulation and mixing: Studies in the Greenland and Norwegian seas. Ph.D. Dissertation, University of Califorina, San Diego, La Jolla, 172pp. Bullister J.L. (1989) Chlorofluorocarbons as time-dependent tracers in the ocean. Oceanography 2, 12-17.

How do environmental processes affect the age of chlorofluorocarbons?

Many processes occur during recharge and in the groundwater environment that can affect CFC concentrations beyond those set by air-water equilibrium, and consequently affect interpretation of apparent age. Table 2 lists the most important processes, their effect on apparent CFC age, and relative importance.