Department of Environmental Engineering, Technical University of Denmark, Miljoevej, Building 113, 2800 Kgs. Lyngby, Denmark.
J Contam Hydrol. 2010 Mar 1;112(1-4):77-90. doi: 10.1016/j.jconhyd.2009.10.008. Epub 2009 Oct 31.
Clayey tills contaminated with chlorinated solvents are a threat to groundwater and are difficult to remediate. A numerical model is developed for assessing leaching processes and for simulating the remediation via enhanced anaerobic dechlorination. The model simulates the transport of a contaminant in a single fracture-clay matrix system coupled with a reactive model for anaerobic dechlorination. The model takes into account microbially driven anaerobic dechlorination, where sequential Monod kinetics with competitive inhibition is used to model the reaction rates, and degradation is localized to account for potential pore size limitations on microbial entry to the clay matrix. The model is used to assess the distribution of TCE and its daughter products in the clay matrix and the concentration of the different compounds at the outlet of the fracture. The time frame for complete cleanup and the contaminant flux out of the clay system are assessed for different distributions of microbial degradation. Results from a set of scenarios show that time to remove 90% of the initial mass is halved when dechlorination occurs in a 5cm reaction zone in the clay at the fracture-matrix interface (from 419 to 195years) and decreases by an order of magnitude when dechlorination occurs in the entire matrix (to 32years). The fracture spacing and the microbial parameters are shown to be the critical parameter for estimation of time frames depending on the system in question. Generally, the system is more sensitive to the physical processes, mainly diffusion in the matrix, than to the biogeochemical processes, when dechlorination is assumed to take place in a limited reaction zone only. The inclusion of sequential dechlorination in clay fracture transport models is crucial, as the contaminant flux to the aquifer will increase as a result of degradation due to the higher mobility of the formed daughter products DCE and VC. The model is used to examine the relationship between flux reduction and mass removal for fractured clay systems.
黏土地层中的受氯代溶剂污染的土壤会对地下水造成威胁，且难以修复。本文开发了一个数值模型，用于评估浸出过程，并通过强化厌氧脱氯来模拟修复。该模型模拟了在单裂隙-黏土基质系统中的污染物运移，并结合了用于厌氧脱氯的反应模型。模型考虑了微生物驱动的厌氧脱氯，其中使用顺序 Monod 动力学和竞争抑制来模拟反应速率，并将降解本地化，以考虑微生物进入黏土基质的潜在孔径限制。该模型用于评估 TCE 及其子产物在黏土基质中的分布以及在裂隙出口处不同化合物的浓度。对于不同的微生物降解分布，评估了完全清理所需的时间框架和污染物从黏土系统中的通量。一组情景的结果表明，当在裂隙-基质界面处的黏土中的 5cm 反应区中发生脱氯时（从 419 年减少到 195 年），去除初始质量的 90%所需的时间减少了一半，而当脱氯发生在整个基质中时，减少了一个数量级（至 32 年）。裂隙间距和微生物参数被证明是根据所研究的系统估计时间框架的关键参数。一般来说，当假设脱氯仅发生在有限的反应区时，系统对物理过程（主要是基质中的扩散）比对生物地球化学过程更为敏感。在黏土裂隙运移模型中包含顺序脱氯至关重要，因为由于形成的子产物 DCE 和 VC 的更高迁移率，向含水层的污染物通量会增加，从而导致降解。该模型用于研究裂隙黏土系统中通量减少与质量去除之间的关系。
