High-frequency dual-tracer approach to identify contaminant transport pathways and quantify migration behaviors in karst underground river system

IF 6.3 1区地球科学 Q1 ENGINEERING, CIVIL

Journal of Hydrology Pub Date : 2025-07-17 DOI:10.1016/j.jhydrol.2025.133935

Huaisong Ji , Gabriele Chiogna , Beatrice Richieri , Xinyang Fan , Kun Huang , Chen Chen , Huaishui Yang , Mingming Luo , Heng Zhao

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Abstract

Karst aquifers heterogeneity presents significant challenges in deciphering pollutant transport mechanisms. To better understand the multi-pathway transport of pollutants and their lag effects in karst underground river systems, we propose a dual-tracer approach that integrates the dynamics of natural pollutants and artificial tracer experiments. Here, we couple the continuous input characteristics of acid mine drainage (AMD) with the pulse injection of dye tracers at the Qingxisi (QXS) underground river system. By using high-frequency hydrogeochemical data and dual-tracer quantitative analysis, this study systematically investigates the different transport behaviors of pollutants in the complex karst system. Results show that: (i) Three hydraulically distinct conduit pathways are newly revealed in the study sites, two of which are found to transport the AMD pollutants for more than 10 km. The migration velocities of the two conduits differ significantly by 3 to 6 times, resulting in a two-stage lagged response in the pollutant peaks during storm events; (ii) The transient pulses shown in the breakthrough curves (BTC) of the artificial tracers strongly contrast to the sustained characteristics of AMD pollutants. We found that the combined use of artificial tracers and AMD enables a comprehensive characterization of the transport dynamics in karst systems; (iii) A conceptual model of pollutant migration is proposed. This model captures a sequence of interconnected processes including intermittent pollutant input driven by stormflow, preferential migration through fast and slow conduits, transient storage within fractures and matrix, and subsequent secondary release. This study underscores the complementarity and applicability of adopting a high-frequency dual-tracer framework that contributes to improved understanding of the dynamic pollutant transport processes and mechanisms in karst systems.

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高频双示踪法识别喀斯特地下河系统中污染物的运移路径和量化迁移行为

喀斯特含水层的非均质性对破译污染物运移机制提出了重大挑战。为了更好地理解喀斯特地下河系统中污染物的多途径运移及其滞后效应，我们提出了一种将天然污染物动力学和人工示踪实验相结合的双示踪方法。在青溪寺（QXS）地下河系统中，我们将酸性矿井水（AMD）的连续输入特性与染料示踪剂的脉冲注入进行了耦合。利用高频水文地球化学数据和双示踪定量分析，系统研究了复杂岩溶系统中污染物的不同输运行为。结果表明：(1)研究地点新发现了3条水力不同的通道，其中2条通道可将AMD污染物输送10公里以上。两个管道的迁移速度相差3 ~ 6倍，导致暴雨期间污染物峰值的两阶段滞后响应；（ii）人工示踪剂的突破曲线（BTC）显示的瞬态脉冲与AMD污染物的持续特征形成强烈对比。研究发现，人工示踪剂和AMD的联合使用能够全面表征岩溶系统的输运动力学；（三）提出了污染物迁移的概念模型。该模型捕捉了一系列相互关联的过程，包括由暴雨流驱动的间歇性污染物输入，通过快速和缓慢管道的优先迁移，裂缝和基质中的短暂储存，以及随后的二次释放。该研究强调了采用高频双示踪剂框架的互补性和适用性，有助于提高对喀斯特系统中动态污染物运移过程和机制的理解。

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来源期刊

Journal of Hydrology 地学-地球科学综合

CiteScore

11.00

自引率

12.50%

发文量

1309

审稿时长

7.5 months

期刊介绍： The Journal of Hydrology publishes original research papers and comprehensive reviews in all the subfields of the hydrological sciences including water based management and policy issues that impact on economics and society. These comprise, but are not limited to the physical, chemical, biogeochemical, stochastic and systems aspects of surface and groundwater hydrology, hydrometeorology and hydrogeology. Relevant topics incorporating the insights and methodologies of disciplines such as climatology, water resource systems, hydraulics, agrohydrology, geomorphology, soil science, instrumentation and remote sensing, civil and environmental engineering are included. Social science perspectives on hydrological problems such as resource and ecological economics, environmental sociology, psychology and behavioural science, management and policy analysis are also invited. Multi-and interdisciplinary analyses of hydrological problems are within scope. The science published in the Journal of Hydrology is relevant to catchment scales rather than exclusively to a local scale or site.