Chlorofluorocarbons as tracers of groundwater transport processes in a shallow, silty sand aquifer
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Abstract
Detailed depth profiles of Chlorofluorocarbons CFC-11(CFCl3(, CFC-12 (CF2Cl2) and CFC-113 (C2F3Cl3) have been obtained from a well-characterized field site in central Ontario. Aquifer materials comprise predominantly silty sands, with a mean organic carbon content of 0.03%. Nearly one-dimensional flow exists at this site, and the vertical migration of a well-defined 3H peak has been tracked through time. Detailed vertical sampling has allowed CFC tracer velocities to be estimated to within 10%. Comparison with 3H profiles enables estimation of chlorofluorocarbon transport parameters. CFC-12 appears to be the most conservative of the CFCs measured. Sorption at this site is low (Kd < 0.03), and degradation does not appear to be important. CFC- 113 is retarded both with respect to CFC-12 and with respect to 3H (Kd = 0.09−0.14). CFC-11 appears to be degraded both in the highly organic unsaturated zone and below 3.5 m depth in the aquifer, where dissolved oxygen concentrations decrease to below 0.5 mg L−1. The half-life for CFC-11 degradation below 3.5 m depth is less than 2 years. While apparent CFC-12 ages match hydraulic ages to within 20% (up to 30 years), apparent CFC-11 and CFC-113 ages significantly overestimate hydraulic ages at our field site.
Suggested Citation
Cook, P., Solomon, D.K., Plummer, N., Busenberg, E., Schiff, S., 1995, Chlorofluorocarbons as tracers of groundwater transport processes in a shallow, silty sand aquifer: Water Resources Research, v. 31, no. 3, p. 425-434, https://doi.org/10.1029/94WR02528.
ISSN: 1944-7973 (online)
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Chlorofluorocarbons as tracers of groundwater transport processes in a shallow, silty sand aquifer |
| Series title | Water Resources Research |
| DOI | 10.1029/94WR02528 |
| Volume | 31 |
| Issue | 3 |
| Publication Date | July 09, 2010 |
| Year Published | 1995 |
| Language | English |
| Publisher | American Geophysical Union |
| Contributing office(s) | Toxic Substances Hydrology Program |
| Description | 10 p. |
| First page | 425 |
| Last page | 434 |