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235-2 Unraveling the effects of residence time and temperature on arsenic mobilization in geothermal groundwater

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

Presenting Author:

Shiping Xing

Authors:

Xing, Shiping¹, Guo, Huaming², Gao, Zhipeng³, Xu, Sheng⁴, Lin, Wenjing⁵, Kersten, Michael⁶

(1) State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), 100083, China, Beijing, Beijing, China; Key Laboratory of Groundwater Conservation of MWR, MOE Key Laboratory of Groundwater Circulation and Environment Evolution, and School of Water Resources and Environment, China University of Geosciences (Beijing), 100083, China, Beijing, Beijing, China, (2) State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), 100083, China, Beijing, Beijing, China; Key Laboratory of Groundwater Conservation of MWR, MOE Key Laboratory of Groundwater Circulation and Environment Evolution, and School of Water Resources and Environment, China University of Geosciences (Beijing), 100083, China, Beijing, Beijing, China, (3) State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences (Beijing), 100083, China, Beijing, (None), China; Key Laboratory of Groundwater Conservation of MWR, MOE Key Laboratory of Groundwater Circulation and Environment Evolution, and School of Water Resources and Environment, China University of Geosciences (Beijing), 100083, China, Beijing, Beijing, China, (4) Institute of Surface Earth System Science, and School of Earth System Science, Tianjin University, Tianjin 300072, China, Tianjin, (None), China, (5) Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang, China, Shijiazhuang, Hebei, China, (6) Environmental Geochemistry Group, Institute of Geosciences, Johannes Gutenberg-University, Mainz, 55099, Germany, Mainz, Germany,

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 Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7103

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

Description

Session Format: Oral

Presentation Date: 10/22/2025

Presentation Start Time: 08:20 AM

Presentation Room: HBGCC, 210AB

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