TY - JOUR
T1 - New perspectives on the use of Ra-224/Ra-228 and Rn-222/Ra-226 activity ratios in groundwater studies
AU - Diego-Feliu, M.
AU - Rodellas, V.
AU - Saaltink, M. W.
AU - Goyetche, T.
AU - Martínez-Pérez, L.
AU - Folch, A.
AU - Garcia-Orellana, J.
AU - Alorda Kleinglas, Aaron
N1 - Funding Information:
This work was partly funded by the projects PID2019-110212RB-C22, CGL2016-77122-C2-1-R/2-R and PID2019-110311RB-C21 of the Spanish Government and the project TerraMAr ACA210/18/00007 of the Catalan Water Agency. The authors want to thank the support of the Generalitat de Catalunya to MERS (2017 SGR-1588) and GHS (2017 SGR 1485) for additional funding. We would like to thank all the colleagues from the Laboratori de Radioactivitat Ambiental (Universitat Aut?noma de Barcelona). We would also like to thank Leon Humphries for his detailed English corrections. We would like to thank SIMMAR (Serveis Integrals de Manteniment del Maresme) and the Consell Comarcal del Maresme in the construction of the research site. M. Diego?Feliu acknowledges the economic support from the FI?2017 fellowships of the Generalitat de Catalunya autonomous government (2017FI_B_00365). V. Rodellas acknowledges financial support from the Beatriu de Pin?s postdoctoral program of the Generalitat de Catalunya autonomous government (2017?BP?00334). A. Alorda?Kleinglass acknowledges financial support from ICTA ?Unit of Excellence? (MinECo, MDM2015?0552?17?1) and PhD fellowship, BES?2017?080740. T. Goyetche acknowledges PhD fellowship (BES?2017?080028) from the FPI Program by the Spanish Ministry of Economy, Industry and Competitiveness. A. Folch is a Serra H?nter Fellow.
Publisher Copyright:
© 2021 Elsevier B.V.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
PY - 2021/5/1
Y1 - 2021/5/1
N2 - The naturally occurring Ra isotopes (223Ra; T1/2 = 11.4 d, 224Ra; T1/2 = 3.66 d, 226Ra; T1/2 = 1,600 y, and 228Ra; T1/2 = 5.7 y) and Rn (222Rn; T1/2 = 3.82 d) have been widely applied as environmental tracers. The application of these radioactive tracers has mainly been restricted to the evaluation of oceanographic and land-ocean interaction processes, although in recent years their use has also been extended to the study of groundwater systems. In this context, the activity ratios of 224Ra/228Ra and 222Rn/226Ra can be instrumental in providing key information on groundwater transit times in aquifers and those processes governing groundwater discharge into the coastal sea (often referred to as Submarine Groundwater Discharge or SGD). This work evaluates the potential use of these activity ratios as proxies for investigating groundwater systems through an advective transport model that integrates the radionuclides involved in these activity ratios (224Ra, 228Ra, 226Ra, and 222Rn) and their immediate parents into a single formulation. The results provided by the transport model indicate that the main factors controlling the 224Ra/228Ra and 222Rn/226Ra activity ratios are the alpha recoil supply, the retardation factor of Ra, and the groundwater transit times. The advective transport model and the activity ratios are used to present novel applications that interrelate the disciplines of hydrogeology and coastal oceanography. The main applications include the determination of groundwater transit times and the assessment of pathways and end-members related to submarine groundwater discharge processes. These applications were tested in a Mediterranean coastal aquifer.
AB - The naturally occurring Ra isotopes (223Ra; T1/2 = 11.4 d, 224Ra; T1/2 = 3.66 d, 226Ra; T1/2 = 1,600 y, and 228Ra; T1/2 = 5.7 y) and Rn (222Rn; T1/2 = 3.82 d) have been widely applied as environmental tracers. The application of these radioactive tracers has mainly been restricted to the evaluation of oceanographic and land-ocean interaction processes, although in recent years their use has also been extended to the study of groundwater systems. In this context, the activity ratios of 224Ra/228Ra and 222Rn/226Ra can be instrumental in providing key information on groundwater transit times in aquifers and those processes governing groundwater discharge into the coastal sea (often referred to as Submarine Groundwater Discharge or SGD). This work evaluates the potential use of these activity ratios as proxies for investigating groundwater systems through an advective transport model that integrates the radionuclides involved in these activity ratios (224Ra, 228Ra, 226Ra, and 222Rn) and their immediate parents into a single formulation. The results provided by the transport model indicate that the main factors controlling the 224Ra/228Ra and 222Rn/226Ra activity ratios are the alpha recoil supply, the retardation factor of Ra, and the groundwater transit times. The advective transport model and the activity ratios are used to present novel applications that interrelate the disciplines of hydrogeology and coastal oceanography. The main applications include the determination of groundwater transit times and the assessment of pathways and end-members related to submarine groundwater discharge processes. These applications were tested in a Mediterranean coastal aquifer.
KW - Alpha recoil
KW - End-member
KW - Groundwater transit times
KW - Radium
KW - Radon
KW - SGD
UR - http://www.scopus.com/inward/record.url?scp=85102975703&partnerID=8YFLogxK
U2 - 10.1016/j.jhydrol.2021.126043
DO - 10.1016/j.jhydrol.2021.126043
M3 - Article
AN - SCOPUS:85102975703
VL - 596
JO - Journal of Hydrology
JF - Journal of Hydrology
SN - 0022-1694
M1 - 126043
ER -