HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Engesgaard, P. Articles by Plummer, L. N. Search for Related Content PubMed Articles by Engesgaard, P. Articles by Plummer, L. N. GeoRef GeoRef Citation Agricola Articles by Engesgaard, P. Articles by Plummer, L. N. Related Collections Field-Scale Studies Other Contaminants Organic Compounds

Transport and Time Lag of Chlorofluorocarbon Gases in the Unsaturated Zone, Rabis Creek, Denmark

^a Geological Institute, Univ. of Copenhagen, Øster Voldgade 10, 1350 Copenhagen K, Denmark
^b Geological Survey of Denmark and Greenland, Øster Voldgade 10, 1350 Copenhagen K, Denmark
^c Environment and Resources, Technical Univ. of Denmark, Building 204, 2800 Lyngby, Denmark
^d USGS, 12201 Sunrise Valley Drive, Reston, VA 20192, USA

View larger version (34K): [in a new window]   Fig. 1. Physical and chemical processes affecting CFC transport in the unsaturated zone.

View larger version (18K): [in a new window]   Fig. 2. Measured and reconstructed (a) CFC-11, (b) CFC-12, and (c) CFC-113 concentration curves for the atmosphere at monitoring stations in Ireland (solid line) and USA (dashed line). Two different measurements of the atmospheric CFC concentrations at the Rabis Creek study site are included.

View larger version (16K): [in a new window]   Fig. 3. Measured water content in the unsaturated zone (June 1995). The mean water content is approximately 6%.

View larger version (47K): [in a new window]   Fig. 4. Simulated results for daily depth-averaged water content and yearly infiltration rate.

View larger version (33K): [in a new window]   Fig. 5. Measured and simulated distributions of CFCs in the unsaturated zone. Note the small range in concentration scale. Horizontal lines connect replicate analyses of separate ampoules.

View larger version (23K): [in a new window]   Fig. 6. Simulated (numerical as solid line and displaced by time lag as solid-dot) CFC concentrations at the water table beneath a 16-m-thick unsaturated zone at the Rabis Creek site compared with atmospheric concentrations (Colorado, USA).

View larger version (22K): [in a new window]   Fig. 7. Simulated time lag for 1983 atmospheric CFC-11 concentration as a function of steady infiltration qw. Two cases of constant water content are shown: w = 0.1 and 0.15. The corresponding simulated time lag for nonsteady infiltration is 4.7 yr. The analytical time lag under linear atmospheric increase in concentration is 5.2 yr.

View larger version (33K): [in a new window]   Fig. 8. Effect of water content, depth of unsaturated zone, and tortuosity coefficient on calculated time lags for CFC-11 and CFC-12 during exponential and linear increase in atmospheric concentrations. (a–c) = 0.1; (d–f) = 0.36.