Carbon and methane cycling in arsenic-contaminated aquifers

Emiliano Stopelli; Vu T Duyen; Henning Prommer; Martyna Glodowska; Andreas Kappler; Magnus Schneider; Elisabeth Eiche; Alexandra K Lightfoot; Carsten J Schubert; Pham K T Trang; Pham H Viet; Rolf Kipfer; Lenny H E Winkel; Michael Berg; AdvectAs team members

doi:10.1016/j.watres.2021.117300

Carbon and methane cycling in arsenic-contaminated aquifers

Water Res. 2021 Jul 15:200:117300. doi: 10.1016/j.watres.2021.117300. Epub 2021 May 27.

Authors

Affiliations

¹ Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department Water Resources and Drinking Water, 8600 Dübendorf, Switzerland. Electronic address: emiliano.stopelli@eawag.ch.
² Key Laboratory of Analytical Technology for Environmental Quality and Food Safety (KLATEFOS), VNU University of Science, Vietnam National University, Hanoi, Vietnam.
³ CSIRO Land and Water, 6014 Floreat, WA, Australia; School of Earth Sciences, University of Western Australia, Crawley, WA 6009, Australia.
⁴ Geomicrobiology, Center for Applied Geosciences, University of Tübingen, 72076 Tübingen, Germany.
⁵ Institute of Applied Geosciences, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
⁶ Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department Water Resources and Drinking Water, 8600 Dübendorf, Switzerland.
⁷ Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department Surface Waters Research & Management, 6047 Kastanienbaum, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zurich, Switzerland.
⁸ Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department Water Resources and Drinking Water, 8600 Dübendorf, Switzerland; Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zurich, Switzerland.
⁹ Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department Water Resources and Drinking Water, 8600 Dübendorf, Switzerland; UNESCO Chair on Groundwater Arsenic within the 2030 Agenda for Sustainable Development, School of Civil Engineering and Surveying, University of Southern Queensland, QLD 4350, Australia. Electronic address: michael.berg@eawag.ch.
¹⁰ AdvectAs team members-listed in the SI.

PMID: 34107428
DOI: 10.1016/j.watres.2021.117300

Abstract

Geogenic arsenic (As) contamination of groundwater is a health threat to millions of people worldwide, particularly in alluvial regions of South and Southeast Asia. Mitigation measures are often hindered by high heterogeneities in As concentrations, the cause(s) of which are elusive. Here we used a comprehensive suite of stable isotope analyses and hydrogeochemical parameters to shed light on the mechanisms in a typical high-As Holocene aquifer near Hanoi where groundwater is advected to a low-As Pleistocene aquifer. Carbon isotope signatures (δ¹³C-CH₄, δ¹³C-DOC, δ¹³C-DIC) provided evidence that fermentation, methanogenesis and methanotrophy are actively contributing to the As heterogeneity. Methanogenesis occurred concurrently where As levels are high (>200 µg/L) and DOC-enriched aquitard pore water infiltrates into the aquifer. Along the flowpath to the Holocene/Pleistocene aquifer transition, methane oxidation causes a strong shift in δ¹³C-CH₄ from -87‰ to +47‰, indicating high reactivity. These findings demonstrate a previously overlooked role of methane cycling and DOC infiltration in high-As aquifers.

Keywords: Carbon isotope δ(13)C; Drinking water; Geogenic As contamination; Groundwater quality; Heterogeneity; Organic matter.

MeSH terms

Arsenic* / analysis
Carbon
Environmental Monitoring
Groundwater*
Humans
Methane
Water Pollutants, Chemical* / analysis

Substances

Water Pollutants, Chemical
Carbon
Arsenic
Methane