Isotopically Enriched Geogenic δ 81 Br and δ 37 Cl: Primary Evidence for the Ascending Brine Model.

Autor: Saeed W; Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada., Shouakar-Stash O; Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada.; School of Engineering, University of Guelph, 50 Stone Road East, Guelph, Ontario, Canada, N1G 2W2.; Isotope Tracer Technologies Inc., 695 Rupert St., Waterloo, Ontario, Canada, N2V 1Z5., Wood WW; Department of Earth and Environmental Sciences, Michigan State University, 288 Farm Lane, East Lansing, MI, 48824, USA., Frape S; Department of Earth and Environmental Sciences, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, N2L 3G1, Canada.
Jazyk: angličtina
Zdroj: Ground water [Ground Water] 2021 Sep; Vol. 59 (5), pp. 671-676. Date of Electronic Publication: 2021 Mar 26.
DOI: 10.1111/gwat.13096
Abstrakt: Mass balance calculations and hydrodynamics of groundwater flow suggest that the solutes in brines of the coastal sabkha aquifer from the Emirate of Abu Dhabi are derived largely from ascending geologic brines into the sabkha from the underlying formations. Solute interpretation for the ascending brine model (ABM) was based on two independent but secondary lines of evidence (solute ratios and solute fluxes). In the current study, direct primary evidence for this ABM was provided through analyses of δ 81 Br, δ 37 Cl, and 87 Sr/ 86 Sr. Different solute histories of geologic brine and sea water provide an "isotopic fingerprint" that can uniquely distinguish between the two possible sources. Samples from the coastal sabkha aquifer of Abu Dhabi were determined to have a mean δ 81 Br of 1.17‰ that is statistically equal, at the 95% confidence level, to the mean of 1.11‰ observed in the underlying geologic brine and statistically different than sea water. Similarly, the δ 37 Cl in sabkha brine has a mean of 0.25‰ and is statistically equal to a mean of 0.21‰ in the underlying geologic brines at the 95% confidence level and statistically different from sea water. Also, dissolved strontium isotope data are consistent with the ABM and even with the complex set of processes in the sabkha, the variance in strontium isotope results is similar to the geologic brine. These observations provide primary direct evidence consistent that the major source of these solutes (and presumably others in the aquifer) is from discharging geologic brines, not from adjacent sea water.
(© 2021 National Ground Water Association.)
Databáze: MEDLINE
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