Advected carbon younger than the sediment fuels microbial metabolism in a pumped deep aquifer
Year: 2026
Type: article
Abstract: Ever deeper wells are drilled worldwide to pump potable groundwater. Recent studies argue that overpumping compresses clays and releases reactive dissolved organic carbon (DOC), which in turn drives a series of microbial reactions that affect groundwater potability including arsenic concentrations. Here, we use a novel method to measure the radiocarbon ages of microbial RNA to determine the source of reactive or metabolizable DOC and argue against the compression of clays as the sole source of carbon. We show that microbial RNA (5,230; 5,550; 6,250 yr; n = 3 wells), DOC (280-10,800 yr; n = 13), and methane (modern to 6,240 yr; n = 3), from an overpumped deep aquifer in Bangladesh are much younger than the overlying clay layers deposited during the Pleistocene over 12,000 years ago. Mass-balance indicates that at least half of the carbon incorporated into RNA has to come from reactive DOC or methane that is advected downward via vertical recharge. This metabolism of advected organic carbon could have implications for the quality of water pumped from deep aquifers. Microbial RNA, dissolved organic carbon, and methane from an overpumped deep aquifer in Bangladesh are advected downward via vertical recharge and are much younger than the overlying clay layers deposited during the Pleistocene over 12,000 years ago, according to radiocarbon analysis
Authors: Brian J. Mailloux, Kazi Matin Ahmed, Afsana Akter, Sarah Blau, Benjamin Bostick, Bruce A. Buchholz, Imtiaz Choudhury, Tyler Ellis, Charles Harvey, Mahfuzur Khan, Madeleine Killough, Maggie C. Y. Lau Vetter, Holly Michael, Rajib Mozumder, Katharine Scanlan, Greg Slater, Elizabeth Trembath-Reichert, Alexander van Geen
Institutions: Columbia University, Barnard College, University of Dhaka, Lamont-Doherty Earth Observatory, Lawrence Livermore National Laboratory, Massachusetts Institute of Technology, Chinese Academy of Sciences, Institute of Deep-Sea Science and Engineering, University of Delaware, McMaster University, Arizona State University
Language: English
Subfield: Geochemistry and Petrology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,490
Awards: G1088636562, G1356433355, G14554683, G1716777315, G2145270357, G3669113783, CNH: Competing Demands and Future Vulnerability of Groundwater: Drinking Water Quality and Food Security in Arsenic-Impacted South and Southeast Asia, Health Effects and Geochemistry of Arsenic, G6139756635, National User Resource for Biological Accelerator Mass Spectrometry, G895790057, G9000217211, Columbia University and Northern Plains Partnership for the Superfund Research Program, G991281326
OpenAlex ID: W7160615757