235 Advancing the Understanding and Management of Groundwater Pollution with Arsenic and Other Geogenic Contaminants Using Geospatial Tools, Machine Learning, and Data Science, Part I

The growing trend of data aggregation and analysis, along with emerging technologies like machine learning, has significantly improved our understanding of groundwater basins, enabling better assessments of water quality for direct consumption and treatment in groundwater supply management.

Wednesday, 22 October 2025
8:00 AM - 12:00 PM
HBGCC, 210AB

Unraveling the effects of residence time and temperature on arsenic mobilization in geothermal groundwater

Paper number: 235-2
Program: Technical Sessions
Time: 8:20 AM – 8:35 AM

Authors

  • Shiping Xing Presenting Author
    State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), 100083, China, Beijing, Beijing
  • Huaming Guo
    State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), 100083, China, Beijing, Beijing
  • Zhipeng Gao
    State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), 100083, China, Beijing, (None)
  • Sheng Xu
    Institute of Surface Earth System Science, and School of Earth System Science, Tianjin University, Tianjin 300072, China, Tianjin, (None)
  • Wenjing Lin
    Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang, China, Shijiazhuang, Hebei
  • Michael Kersten
    Environmental Geochemistry Group, Institute of Geosciences, Johannes Gutenberg-University, Mainz, 55099, Germany, Mainz

Abstract

Geothermally sourced arsenic (As) is known to occur worldwide, and its presence is controlled by groundwater temperature and residence time. However, the respective roles of these factors in As mobilization remain unclear. In this study, radiocarbon isotopes of dissolved inorganic carbon in geothermal groundwater from the Gonghe Basin of the northeastern Tibetan Plateau were analyzed to investigate the influence of groundwater residence time and temperature on As mobilization. Geothermal groundwater from the Neogene and Quaternary aquifers had temperature ranging from 15.3 to 98.0 ℃, which were significantly higher than those of cold groundwater from the Quaternary aquifer (from 10.1 to 15.0 ℃) (p<0.01). A wide range of As concentrations was found in groundwater, ranging from 0.3 to 1130 μg/L. Geothermal groundwater exhibited significantly higher As concentrations, with an average of 96.9 μg/L, compared to cold groundwater, which averaged 2.10 μg/L (p < 0.01). The groundwater residence time ranged widely from 0.49 to 32.8 ka, with geothermal groundwater (from 1.65 to 32.8 ka) showing significantly longer residence time than cold groundwater (from 0.49 to 2.74 ka) (p < 0.01). Both groundwater residence time and temperature were positively correlated with As concentrations, which demonstrated that longer residence time and higher temperature facilitated As enrichment. Higher groundwater temperature creates thermal conditions to increase mineral solubility and reaction rates, promoting the dissolution of As-bearing minerals and accelerating the degradation of dissolved organic matter, both of which enhance As mobilization and enrichment in groundwater. Arsenic adsorption also decreases at elevated groundwater temperature since the process is exothermic. Prolonged groundwater residence time tends to increase As concentrations, as geochemical reactions related to As mobilization (such as reductive dissolution of ferric (hydro)oxide minerals and silicate weathering) are kinetically constrained, and thus proceed further with longer groundwater-rock contact. This study highlights the crucial roles of both residence time and temperature in As mobilization in geothermal groundwater.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412571

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.