Abstract The rapid increase in production and application of nanoparticles (NPs) across a wide range of commercial and industrial processes has resulted in the extensive invasion of NPs into subsurface environments. Accurately predicting the transport and release of NPs in subsurface environments is important for assessing a wide range of environmental and human health risks. In this study, a two-dimensional NP transport and release model was proposed to investigate the behavior of NPs in a layered heterogeneous medium with transient ionic strength (IS). The layered heterogeneous porous medium comprised a slow flow domain (SFD) and a fast flow domain (FFD). The transport of NPs in the two layers was described by two coupled advection–dispersion equations (ADEs). The NP deposition and release were related to the IS of the electrolyte solution (ES) in the medium and were represented by reversible and irreversible deposition terms in the ADEs. The results indicated that heterogeneity has a significant impact on the transport and release of NPs. When NPs pass through the two‐layer medium, initially part of the NPs in the FFD will migrate into the SFD. A larger amount of NPs are deposited in the SFD than the FFD owing to the higher filtration capacity of the SFD. The retained NPs in both the SFD and FFD will be released when the IS declines. The release of the retained NPs in the FFD is faster than that in the SFD because the FFD has a higher intrinsic release rate and lower IS owing to the more rapid transport of ES in the FFD. The proposed model was applied to laboratory experiments and compared to the double-region model. The proposed model fitted the experimental breakthrough curves better than the double-region model, and it is capable of fitting the release of NPs, which cannot be accomplished with the double-region model.

中文翻译：

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瞬态化学条件下纳米颗粒在层状非均质多孔介质中的传输和释放

摘要 在广泛的商业和工业过程中，纳米颗粒 (NPs) 的生产和应用迅速增加，导致纳米颗粒广泛侵入地下环境。准确预测 NPs 在地下环境中的传输和释放对于评估广泛的环境和人类健康风险非常重要。在这项研究中，提出了二维纳米颗粒传输和释放模型来研究纳米颗粒在具有瞬态离子强度 (IS) 的分层异质介质中的行为。层状非均质多孔介质包括慢流域 (SFD) 和快流域 (FFD)。两层中 NP 的传输由两个耦合平流-弥散方程 (ADE) 描述。NP 沉积和释放与介质中电解质溶液 (ES) 的 IS 相关，并由 ADE 中的可逆和不可逆沉积项表示。结果表明，异质性对纳米颗粒的运输和释放有显着影响。当 NPs 通过两层介质时，最初 FFD 中的部分 NPs 将迁移到 SFD 中。由于 SFD 的过滤能力更高，因此在 SFD 中沉积的 NPs 比 FFD 中沉积的量更大。当 IS 下降时，SFD 和 FFD 中保留的 NP 将被释放。FFD 中保留的 NPs 的释放比 SFD 中的快，因为 FFD 具有更高的内在释放速率和更低的 IS，这是由于 FFD 中 ES 的运输速度更快。将所提出的模型应用于实验室实验并与双区域模型进行比较。所提出的模型比双区模型更好地拟合了实验突破曲线，并且能够拟合NPs的释放，这是双区模型无法完成的。