Brusseau M L, Nelson N T, Zhang Z, Blue J E, Rohrer J, Allen T
Soil, Water and Environmental Science Department, USA.
J Contam Hydrol. 2007 Feb 20;90(1-2):21-40. doi: 10.1016/j.jconhyd.2006.09.004. Epub 2006 Oct 16.
An extensive site-characterization project was conducted at a large chlorinated-solvent contaminated Superfund site in Tucson, AZ. The project consisted of several components, including traditional site-characterization activities, tracer tests, laboratory experiments conducted with core material collected from the site, and mathematical modeling. The primary focus of the work presented herein is the analysis of induced-gradient contaminant elution tests conducted in a source zone at the site, investigation of the potential occurrence of immiscible liquid in the saturated zone, characterization of the relationship between mass flux reduction and mass removal, and evaluation of the impact of source-zone management on site remediation. The results of the present study, along with those of prior work, indicate that immiscible liquid is likely present in the saturated zone at the site source zones. Extensive tailing and rebound was observed for the contaminant-elution tests, indicating nonideal transport and mass-transfer behavior. The elution data were analyzed with a source-zone-scale mathematical model, and the results indicated that nonideal immiscible-liquid dissolution was the primary cause of the observed behavior. The time-continuous relationship between mass flux reduction and mass removal associated with the plume-scale pump-and-treat operation exhibited an initial large drop in mass flux with minimal mass removed, followed by a period of minimal mass flux reduction and a second period of large reduction. This behavior reflects the impact of both source-zone and aqueous-plume mass removal dynamics. Ultimately, a greater than 90% reduction in mass flux was achieved for a mass removal of approximately 50%. The influence of source-zone management on site remediation was evaluated by conducting two predictive simulations, one for which the source zones were controlled and one for which they were not. A plume-scale model was used to simulate the composite contaminant concentrations associated with groundwater extracted with the pump-and-treat system, which were compared to measured data. The information generated from this study was used to enhance the site conceptual model, help optimize operation of the pump-and-treat system, and evaluate the utility of source-zone remediation.
在亚利桑那州图森市一个受氯代溶剂污染的大型超级基金场地开展了一项广泛的场地特征描述项目。该项目由几个部分组成，包括传统的场地特征描述活动、示踪剂测试、对从该场地采集的岩芯材料进行的实验室实验以及数学建模。本文所呈现工作的主要重点是分析在该场地一个源区进行的诱导梯度污染物洗脱试验、调查饱和带中不混溶液体的潜在存在情况、表征质量通量降低与质量去除之间的关系以及评估源区管理对场地修复的影响。本研究结果以及先前工作的结果表明，该场地源区的饱和带中可能存在不混溶液体。在污染物洗脱试验中观察到了大量的拖尾和反弹现象，表明存在非理想的传输和传质行为。利用一个源区尺度的数学模型对洗脱数据进行了分析，结果表明非理想的不混溶液体溶解是观察到的行为的主要原因。与羽流尺度抽提处理操作相关的质量通量降低与质量去除之间的时间连续关系显示，质量通量最初大幅下降，而质量去除量最小，随后是质量通量降低最小的时期，接着是第二个大幅降低的时期。这种行为反映了源区和水相羽流质量去除动态的影响。最终，在质量去除约50%的情况下，质量通量降低了90%以上。通过进行两个预测模拟来评估源区管理对场地修复的影响，一个模拟中源区得到控制，另一个模拟中源区未得到控制。使用羽流尺度模型来模拟与抽提处理系统抽取的地下水相关的复合污染物浓度，并将其与实测数据进行比较。本研究生成的信息用于完善场地概念模型、帮助优化抽提处理系统的运行以及评估源区修复的效用。
