Use and application of CFC-11, CFC-12, CFC-113 and SF6 as environmental tracers of groundwater residence time: a review

Chambers, L.A.; Gooddy, D.C.; Binley, A.M.. 2019 Use and application of CFC-11, CFC-12, CFC-113 and SF6 as environmental tracers of groundwater residence time: a review. Geoscience Frontiers, 10 (5). 1643-1652. https://doi.org/10.1016/j.gsf.2018.02.017

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Official URL: http://dx.doi.org/10.1016/j.gsf.2018.02.017

Abstract/Summary

Groundwater residence time is a fundamental property of groundwater to understand important hydrogeological issues, such as deriving sustainable abstraction volumes, or, the evolution of groundwater quality. The anthropogenic trace gases chlorofluorocarbons (CFC-11, CFC-12 and CFC-113) and sulphur hexafluoride (SF6) are ideal in this regard because they have been released globally at known rates and become dissolved in groundwater following Henry's Law, integrating over large spatial (global) and temporal (decades) scales. The CFCs and SF6 are able to date groundwater up to ∼100 years old with the caveat of certain simplifying assumptions. However, the inversion of environmental tracer concentrations (CFCs and SF6) to derive groundwater age rests on the accurate determination of groundwater recharge parameters, namely temperature, elevation, salinity and excess air, in addition to resolving the potential for contamination, degradation and unsaturated zone effects. This review explores the fundamentals of CFC-11, CFC-12, CFC-113 and SF6 as environmental tracers of groundwater age and recommends complementary techniques throughout. Once this relatively simple and inexpensive technique has been used to determine initial concentrations at the recharge zone, setting the groundwater dating ‘clock’ to zero, this review then explores the meaning of groundwater ‘age’ in relation to measured environmental tracer concentrations. It is shown that the CFCs and SF6 may be applied to a wide-range of hydrogeological problems and suggests that environmental tracers are particularly powerful tools when integrated with numerical flow and transport models.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.gsf.2018.02.017
ISSN:	16749871
Additional Keywords:	GroundwaterBGS, Groundwater, Groundwater dating
Date made live:	02 Dec 2019 13:45 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/526086

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1016/j.gsf.2018.02.017

ISSN:

16749871

Additional Keywords:

GroundwaterBGS, Groundwater, Groundwater dating

Date made live:

02 Dec 2019 13:45 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/526086