Document Detail


Degassing of 3H/3He, CFCs and SF6 by denitrification: measurements and two-phase transport simulations.
MedLine Citation:
PMID:  19042054     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The production of N2 gas by denitrification may lead to the appearance of a gas phase below the water table prohibiting the conservative transport of tracer gases required for groundwater dating. We used a two-phase flow and transport model (STOMP) to study the reliability of 3H/3He, CFCs and SF6 as groundwater age tracers under agricultural land where denitrification causes degassing. We were able to reproduce the amount of degassing (R2=69%), as well as the 3H (R2=79%) and 3He (R2=76%) concentrations observed in a 3H/3He data set using simple 2D models. We found that the TDG correction of the 3H/3He age overestimated the control 3He/3He age by 2.1 years, due to the accumulation of 3He in the gas phase. The total uncertainty of degassed 3H/3He ages of 6 years (+/-2 sigma) is due to the correction of degassed 3He using the TDG method, but also due to the travel time in the unsaturated zone and the diffusion of bomb peak 3He. CFCs appear to be subject to significant degradation in anoxic groundwater and SF6 is highly susceptible to degassing. We conclude that 3H/3He is the most reliable method to date degassed groundwater and that two-phase flow models such as STOMP are useful tools to assist in the interpretation of degassed groundwater age tracer data.
Authors:
Ate Visser; Joris D Schaap; Hans Peter Broers; Marc F P Bierkens
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-11-12
Journal Detail:
Title:  Journal of contaminant hydrology     Volume:  103     ISSN:  0169-7722     ISO Abbreviation:  J. Contam. Hydrol.     Publication Date:  2009 Jan 
Date Detail:
Created Date:  2009-01-12     Completed Date:  2009-05-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8805644     Medline TA:  J Contam Hydrol     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  206-18     Citation Subset:  IM    
Affiliation:
Utrecht University, Department of Physical Geography, P.O. Box 80115, 3508 TC Utrecht, The Netherlands. a.visser@geo.uu.nl
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MeSH Terms
Descriptor/Qualifier:
Calibration
Chlorofluorocarbons / chemistry*
Computer Simulation
Gases / chemistry*
Helium / chemistry*
Models, Chemical
Nitrogen / chemistry*,  isolation & purification*
Pressure
Soil
Sulfur Hexafluoride / chemistry*
Tritium / chemistry*
Water / chemistry
Chemical
Reg. No./Substance:
0/Chlorofluorocarbons; 0/Gases; 0/Soil; 10028-17-8/Tritium; 2551-62-4/Sulfur Hexafluoride; 7440-59-7/Helium; 7727-37-9/Nitrogen; 7732-18-5/Water

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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