Numerical investigation of coupled density‐driven flow and hydrogeochemical processes below playas
Numerical investigation of coupled density‐driven flow and hydrogeochemical processes below playas
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DOI：
10.1002/2015wr017833
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发表时间：
2015-11
影响因子：
5.4
通讯作者：
E. Hamann;V. Post;C. Kohfahl;H. Prommer;C. Simmons
中科院分区：
文献类型：
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作者：
E. Hamann;V. Post;C. Kohfahl;H. Prommer;C. Simmons
探讨了不同复杂程度的数值模拟方法，以研究含盐盆地地下水流与地球化学过程的耦合。对干盐湖系统的长期模型模拟深入了解了密度驱动流与沉淀方解石和演化卤水的时空模式之间的复杂反馈机制。使用反应多组分传输模型的方法，模拟再现，第一次在数值研究中，经常观察到的盐盆地（“靶心”）的蒸发沉淀序列。发现特定于盐湖的流动、蒸发浓缩和化学分水岭是形成碳酸盐岩的位置以及由此产生的盐水化学的主要控制因素。与计算要求低得多的替代单物种传输模型的比较模拟表明，这些模型仍然能够复制由更复杂的反应传输模拟获得的主要流型。然而，模拟的盐渍化程度明显低于反应性多组分输运模拟。例如，在模拟的后期阶段，当盐水变成岩盐饱和时，非反应性模拟高估了溶质质量近20%。模拟强调了考虑反应性运输过程的重要性，以了解和量化地球化学模式，个别溶解溶质的浓度，和蒸发岩的演变。
Numerical modeling approaches with varying complexity were explored to investigate coupled groundwater flow and geochemical processes in saline basins. Long‐term model simulations of a playa system gain insights into the complex feedback mechanisms between density‐driven flow and the spatiotemporal patterns of precipitating evaporites and evolving brines. Using a reactive multicomponent transport model approach, the simulations reproduced, for the first time in a numerical study, the evaporite precipitation sequences frequently observed in saline basins (“bull's eyes”). Playa‐specific flow, evapoconcentration, and chemical divides were found to be the primary controls for the location of evaporites formed, and the resulting brine chemistry. Comparative simulations with the computationally far less demanding surrogate single‐species transport models showed that these were still able to replicate the major flow patterns obtained by the more complex reactive transport simulations. However, the simulated degree of salinization was clearly lower than in reactive multicomponent transport simulations. For example, in the late stages of the simulations, when the brine becomes halite‐saturated, the nonreactive simulation overestimated the solute mass by almost 20%. The simulations highlight the importance of the consideration of reactive transport processes for understanding and quantifying geochemical patterns, concentrations of individual dissolved solutes, and evaporite evolution.