Alteration of natural ³⁷Ar activity concentration in the subsurface by gas transport and water infiltration

Guillon, Sophie; Sun, Yunwei; Purtschert, Roland; Raghoo, Lauren Samara; Pili, Eric; Carrigan, Charles R. (2016). Alteration of natural ³⁷Ar activity concentration in the subsurface by gas transport and water infiltration. Journal of environmental radioactivity, 155-156, pp. 89-96. Elsevier 10.1016/j.jenvrad.2016.02.021

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High ³⁷Ar activity concentration in soil gas is proposed as a key evidence for the detection of underground nuclear explosion by the Comprehensive Nuclear Test-Ban Treaty. However, such a detection is challenged by the natural background of ³⁷Ar in the subsurface, mainly due to Ca activation by cosmic rays. A better understanding and improved capability to predict ³⁷Ar activity concentration in the subsurface and its spatial and temporal variability is thus required. A numerical model integrating ³⁷Ar production and transport in the subsurface is developed, including variable soil water content and water infiltration at the surface. A parameterized equation for ³⁷Ar production in the first 15 m below the surface is studied, taking into account the major production reactions and the moderation effect of soil water content. Using sensitivity analysis and uncertainty quantification, a realistic and comprehensive probability distribution of natural ³⁷Ar activity concentrations in soil gas is proposed, including the effects of water infiltration. Site location and soil composition are identified as the parameters allowing for a most effective reduction of the possible range of ³⁷Ar activity concentrations. The influence of soil water content on ³⁷Ar production is shown to be negligible to first order, while ³⁷Ar activity concentration in soil gas and its temporal variability appear to be strongly influenced by transient water infiltration events. These results will be used as a basis for practical CTBTO concepts of operation during an OSI.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Climate and Environmental Physics

UniBE Contributor:

Purtschert, Roland and Raghoo, Lauren Samara

Subjects:

500 Science > 530 Physics

ISSN:

0265-931X

Publisher:

Elsevier

Language:

English

Submitter:

Doris Rätz

Date Deposited:

08 Jul 2016 15:14

Last Modified:

08 Jul 2016 15:14

Publisher DOI:

10.1016/j.jenvrad.2016.02.021

BORIS DOI:

10.7892/boris.82545

URI:

https://boris.unibe.ch/id/eprint/82545

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