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<p>The accurate tracing of multi-artificial recharge sources is crucial for assessing their impacts on groundwater quantity and quality in adjacent aquifers. However, conventional ions and emerging contaminants with non-conservative behavior exhibit limitations in tracing artificially recharged groundwater. Thus, there is an urgent need to identify effective tracers for delineating artificial recharge processes. This study focuses on the multi-artificial recharge area in Chaobai River, Beijing, being recharged by reclaimed water, South-to-North Water Diversion water, and Wenyu River-Chaobai Riverdiversion water. By investigating the attenuation patterns of typical tracers (e.g., Gd/Gd*, Cl<sup>−</sup> concentrations, and <i>δ</i><sup>18</sup>O values) along potential recharge pathways, we quantified the groundwater sources from different recharge zones and revealed their impacts on groundwater quality. Results show that, while hydrogeochemical types and major ion concentrations in groundwater across the three recharge zones were similar, Gd concentrations in groundwater influenced by reclaimed water were 40–50 times higher than those in the other two zones. Using Gd/Gd* as a tracer, the reclaimed water recharge extended laterally up to 1000 m from the river bank and to depths &lt;60 m. The Wenyu River-Chaobai Riverdiversion water affected groundwater within 500 m laterally and &lt;30 m vertically. A three-end-member mixing model based on Cl<sup>−</sup> and <i>δ</i><sup>18</sup>O tracers revealed that the South-to-North Water Diversion recharge predominantly influenced groundwater within 2000 m laterally and &lt;80 m in depth. High-arsenic groundwater was primarily distributed in the southern Wenyu River-Chaobai River diversion zone with limited recharge influence, where arsenic enrichment was linked to the reductive dissolution of arsenic-bearing Fe oxides and HCO<sub>3</sub><sup>−</sup>-driven arsenic desorption. In contrast, groundwater arsenic concentrations were significantly lower in recharge-affected areas and showed a strong negative correlation with Gd/Gd*, indicating that artificial recharge effectively reduced groundwater arsenic levels. This study demonstrates the suitability of rare earth element anomalies (e.g., Gd/Gd*) for tracing reclaimed water recharge and provides a scientific basis for assessing the impacts of multi-source artificial recharge on groundwater quality.</p>

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Sources of groundwater in multi-artificial recharge areas and their influence on arsenic mobility

  • 期刊论文

  • 发表日期：

    2025年7月29日

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  • Huaming Guo,
  • Zhipeng Gao,
  • Yongcai Guo,
  • Yi Zhao

摘要

The accurate tracing of multi-artificial recharge sources is crucial for assessing their impacts on groundwater quantity and quality in adjacent aquifers. However, conventional ions and emerging contaminants with non-conservative behavior exhibit limitations in tracing artificially recharged groundwater. Thus, there is an urgent need to identify effective tracers for delineating artificial recharge processes. This study focuses on the multi-artificial recharge area in Chaobai River, Beijing, being recharged by reclaimed water, South-to-North Water Diversion water, and Wenyu River-Chaobai Riverdiversion water. By investigating the attenuation patterns of typical tracers (e.g., Gd/Gd*, Cl− concentrations, and δ18O values) along potential recharge pathways, we quantified the groundwater sources from different recharge zones and revealed their impacts on groundwater quality. Results show that, while hydrogeochemical types and major ion concentrations in groundwater across the three recharge zones were similar, Gd concentrations in groundwater influenced by reclaimed water were 40–50 times higher than those in the other two zones. Using Gd/Gd* as a tracer, the reclaimed water recharge extended laterally up to 1000 m from the river bank and to depths <60 m. The Wenyu River-Chaobai Riverdiversion water affected groundwater within 500 m laterally and <30 m vertically. A three-end-member mixing model based on Cl− and δ18O tracers revealed that the South-to-North Water Diversion recharge predominantly influenced groundwater within 2000 m laterally and <80 m in depth. High-arsenic groundwater was primarily distributed in the southern Wenyu River-Chaobai River diversion zone with limited recharge influence, where arsenic enrichment was linked to the reductive dissolution of arsenic-bearing Fe oxides and HCO3−-driven arsenic desorption. In contrast, groundwater arsenic concentrations were significantly lower in recharge-affected areas and showed a strong negative correlation with Gd/Gd*, indicating that artificial recharge effectively reduced groundwater arsenic levels. This study demonstrates the suitability of rare earth element anomalies (e.g., Gd/Gd*) for tracing reclaimed water recharge and provides a scientific basis for assessing the impacts of multi-source artificial recharge on groundwater quality.