Print Email Facebook Twitter Dating degassed groundwater with 3H/3He Title Dating degassed groundwater with 3H/3He Author Visser, A. Broers, H.P. Bierkens, M.F.P. TNO Bouw en Ondergrond Publication year 2007 Abstract The production of gases in groundwater under contaminated locations by geochemical and biological processes is not uncommon. Degassing of these gases from groundwater and repartitioning of noble gases between water and gas phase distorts groundwater dating by 3H/3He. We observed noble gas concentrations below atmospheric equilibrium in 20 out of 34 groundwater samples from agriculturally polluted sandy areas in the Netherlands. From the absence of nitrate in degassed samples, we conclude that denitrification causes degassing. The 22Ne/20Ne ratios show that degassing had attained solubility equilibrium and had not caused isotopic fractionation by diffusion. To correct for the loss of tritiogenic 3He due to degassing, we present a single-step equilibrium degassing model. We use the total dissolved gas pressure at the monitoring screen to estimate the depth and timing of degassing, which is essential to estimate travel times from degassed samples. By propagating the uncertainties in the underlying measurements and assumptions through the travel time calculations, we found a travel time uncertainty of 3 years (a). We therefore conclude that 3H/ 3He dating can produce valuable information on groundwater flow even at sites with strong degassing. Copyright 2007 by the American Geophysical Union. Subject GeosciencesConcentration (process)ContaminationDenitrificationNitratesDegassing modelIsotopic fractionationGroundwaterConcentration (process)ContaminationDenitrificationGroundwaterNitratesagricultural runoffdating methoddegassingdenitrificationgroundwater flowgroundwater pollutionhelium isotopeisotopic fractionationtritiumuncertainty analysisBeneluxEurasiaEuropeNetherlandsWestern Europe To reference this document use: http://resolver.tudelft.nl/uuid:70f83a33-25cf-4c88-a8cf-d5bc3299e85c TNO identifier 240222 ISSN 0043-1397 Source Water Resources Research, 43 (10) Article number No.: W10434 Document type article Files To receive the publication files, please send an e-mail request to TNO Library.