Modeling Reactive Solute Transport in Permafrost‐Affected Groundwater Systems
Modeling Reactive Solute Transport in Permafrost‐Affected Groundwater Systems
复制标题
模拟受永久冻土影响的地下水系统中的反应性溶质运移
DOI：
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发表时间：
2021
影响因子：
5.4
通讯作者：
Amy Jackson
中科院分区：
文献类型：
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作者：
A. Mohammed;V. Bense;B. Kurylyk;R. Jamieson;L. Johnston;Amy Jackson
了解地面冻融，地下水流和溶质运移之间的相互作用对于评估多年冻土区污染物的命运至关重要。然而，由于地下物质和能量传输过程之间的内在相互作用和耦合，预测受多年冻土影响的地下水系统中的溶质迁移具有挑战性。为此，我们开发了一个数值模型，该模型考虑了耦合的地下水流，地下热传递和溶质运移，包括水-冰相变，溶质依赖的孔隙水冻结和温度依赖的溶质反应速率。作为一个说明性的例子，我们提出了模拟调查的潜在污染，从城市污水泻湖在加拿大亚北极。二维地下水模型假设不同的多年冻土条件下开发，以评估可能的污染物迁移的情况下，从泻湖到河流的地下水流，包括保守的，可降解的，吸附溶质的运输。模型结果揭示了重要的传输机制控制的行为，在多年冻土景观以及水文地质因素影响反应性运输在寒冷地区的含水污染物。季节性冻融会间歇性地限制运输途径的连通性，从而减弱运输和反应速率。然而，溶质浓度的升高会降低孔隙水的冻结温度，并产生融化诱导的溶质运移。热驱动和溶质增强的融化都可以减少永久冻土中的冰含量，这对溶质迁移具有重要意义。因此，在定量评估环境条件变化对污染物水文地质的影响时，必须考虑控制寒区地下水系统反应性迁移的热水文地质过程。
Understanding the interactions between ground freeze‐thaw, groundwater flow, and solute transport is imperative for evaluating the fate of contaminants in permafrost regions. However, predicting solute migration in permafrost‐affected groundwater systems is challenging due to the inherent interactions and coupling between subsurface mass and energy transport processes. To this end, we developed a numerical model that considers coupled groundwater flow, subsurface heat transfer, and solute transport, including water‐ice phase change, solute‐dependent porewater freezing, and temperature‐dependent solute reaction rates. As an illustrative example, we present simulations to investigate the potential for contamination from a municipal wastewater lagoon in the Canadian sub‐arctic. Two‐dimensional groundwater models assuming varying permafrost conditions were developed to evaluate possible contaminant migration scenarios associated with groundwater flow from the lagoon to a river, including the transport of conservative, degradable, and sorbing solutes. Model results reveal important transport mechanisms controlling the behavior of aqueous contaminants in permafrost landscapes as well as the hydrogeologic factors affecting reactive transport in cold regions. Seasonal freeze‐thaw episodically restricts connectivity of transport pathways, which attenuates both transport and reaction rates. However, elevated solute concentrations can depress the freezing temperature of porewater and produce thaw‐induced solute transport. Both thermally driven and solute‐enhanced thaw can decrease ice content in permafrost, which can have significant implications for solute migration. Therefore, thermo‐hydrogeologic process controlling reactive transport in cold‐region groundwater systems must be considered when quantitatively assessing the impact of changing environmental conditions on contaminant hydrogeology.