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Improving gas-derived parameterization of groundwater using free phase gas measurements

September 16, 2022

Dissolved atmogenic gasses in groundwater provide significant information about recharge conditions, flowpath, and age. Free phase gas in aquifers is largely ignored in these analyses and there is a lack of quantitative analysis for gas flux mechanisms. Many related fields encountering multiphase flow acknowledge that the presence of bubbles allows for the rapid exsolution of dissolved gasses and volatile compounds through diffusive and polar forces. By measuring the mass flow of the exsolved gas at a spring, coupled with compositional analysis in the free and dissolved phases, we show that not incorporating the effects of the free gas phase of bubbling springs introduces error in the estimation of total gas quantities, particularly light noble gasses. This can significantly affect the corresponding estimation of noble gas temperature (NGT) and apparent age. We examine the transport of free and dissolved gas from the recharge zone, using water level variation data, to the discharge location where the gases are measured. This technique of using the free gas phase for assessing aquifer dynamics will improve groundwater conceptual models, particularly in karstic aquifers where rapid fluctuations in the water table facilitate the development of excess air, generating multiphase spring discharge.

Publication Year 2022
Title Improving gas-derived parameterization of groundwater using free phase gas measurements
DOI 10.1039/D2EW00150K
Authors Robert J Agnew, Andrew Hunt, Todd Halihan
Publication Type Article
Publication Subtype Journal Article
Series Title Environmental Science: Water Research & Technology
Index ID 70240763
Record Source USGS Publications Warehouse
USGS Organization Geology, Geophysics, and Geochemistry Science Center