Constraining source attribution of methane in an alluvial aquifer with multiple recharge pathways.

Autor: Iverach CP; School of Biological, Earth and Environmental Sciences, UNSW Sydney, NSW 2052, Australia; Connected Waters Initiative Research Centre, UNSW Sydney, NSW 2052, Australia; Australian Nuclear Science and Technology Organisation, New Illawarra Rd, Lucas Heights, NSW 2234, Australia., Cendón DI; Australian Nuclear Science and Technology Organisation, New Illawarra Rd, Lucas Heights, NSW 2234, Australia; Connected Waters Initiative Research Centre, UNSW Sydney, NSW 2052, Australia., Beckmann S; College of Earth, Ocean and Environment, University of Delaware, 700 Pilottown Road, 19958 Lewes, USA., Hankin SI; Australian Nuclear Science and Technology Organisation, New Illawarra Rd, Lucas Heights, NSW 2234, Australia., Manefield M; School of Civil and Environmental Engineering, School of Chemical Engineering, UNSW Sydney, NSW 2052, Australia., Kelly BFJ; School of Biological, Earth and Environmental Sciences, UNSW Sydney, NSW 2052, Australia; Connected Waters Initiative Research Centre, UNSW Sydney, NSW 2052, Australia. Electronic address: bryce.kelly@unsw.edu.au.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2020 Feb 10; Vol. 703, pp. 134927. Date of Electronic Publication: 2019 Nov 02.
DOI: 10.1016/j.scitotenv.2019.134927
Abstrakt: Identifying the source of methane (CH 4 ) in groundwater is often complicated due to various production, degradation and migration pathways, particularly in settings where there are multiple groundwater recharge pathways. This study demonstrates the ability to constrain the origin of CH 4 within an alluvial aquifer that could be sourced from in situ microbiological production or underlying formations at depth. To characterise the hydrochemical and microbiological processes active within the alluvium, previously reported hydrochemical data (major ion chemistry and isotopic tracers ( 3 H, 14 C, 36 Cl)) were interpreted in the context of CH 4 and carbon dioxide (CO 2 ) isotopic chemistry, and the microbial community composition in the groundwater. The rate of observed oxidation of CH 4 within the aquifer was then characterised using a Rayleigh fractionation model. The stratification of the hydrochemical facies and microbiological community populations is interpreted to be a result of the gradational mixing of water from river leakage and floodwater recharge with water from basal artesian inflow. Within the aquifer there is a low abundance of methanogenic archaea indicating that there is limited biological potential for microbial CH 4 production. Our results show that the resulting interconnection between hydrochemistry and microbial community composition affects the occurrence and oxidation of CH 4 within the alluvial aquifer, constraining the source of CH 4 in the groundwater to the geological formations beneath the alluvium.
(Copyright © 2019 The Author(s). Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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