ENGEO Incorporated, 2010 Crow Canyon Place, Suite 250, San Ramon, CA 94583, USA.
Int J Environ Res Public Health. 2011 Jun;8(6):2226-39. doi: 10.3390/ijerph8062226. Epub 2011 Jun 16.
In-situ air sparging has evolved as an innovative technique for soil and groundwater remediation impacted with volatile organic compounds (VOCs), including chlorinated solvents. These may exist as non-aqueous phase liquid (NAPL) or dissolved in groundwater. This study assessed: (1) how air injection rate affects the mass removal of dissolved phase contamination, (2) the effect of induced groundwater flow on mass removal and air distribution during air injection, and (3) the effect of initial contaminant concentration on mass removal. Dissolved-phase chlorinated solvents can be effectively removed through the use of air sparging; however, rapid initial rates of contaminant removal are followed by a protracted period of lower removal rates, or a tailing effect. As the air flow rate increases, the rate of contaminant removal also increases, especially during the initial stages of air injection. Increased air injection rates will increase the density of air channel formation, resulting in a larger interfacial mass transfer area through which the dissolved contaminant can partition into the vapor phase. In cases of groundwater flow, increased rates of air injection lessened observed downward contaminant migration effect. The air channel network and increased air saturation reduced relative hydraulic conductivity, resulting in reduced groundwater flow and subsequent downgradient contaminant migration. Finally, when a higher initial TCE concentration was present, a slightly higher mass removal rate was observed due to higher volatilization-induced concentration gradients and subsequent diffusive flux. Once concentrations are reduced, a similar tailing effect occurs.
原位空气喷射技术已发展成为一种修复受挥发性有机化合物（VOCs），包括氯化溶剂污染的土壤和地下水的创新技术。这些污染物可能以非水相液体（NAPL）或溶解在地下水中存在。本研究评估了：（1）空气注入速率如何影响溶解相污染物的去除量，（2）诱导地下水流动对空气注入过程中污染物去除和空气分布的影响，以及（3）初始污染物浓度对去除量的影响。溶解态氯化溶剂可以通过空气喷射有效地去除；然而，快速的初始污染物去除率随后是较长时间的低去除率，或拖尾效应。随着空气流速的增加，污染物的去除率也会增加，特别是在空气注入的初始阶段。增加的空气注入速率将增加空气通道形成的密度，从而通过该空气通道形成更大的界面传质面积，溶解污染物可以通过该界面传质面积分配到气相中。在地下水流动的情况下，增加的空气注入速率减轻了观察到的向下污染物迁移效应。空气通道网络和增加的空气饱和度降低了相对水力传导率，导致地下水流量减少，随后污染物向下迁移。最后，当存在较高的初始 TCE 浓度时，由于较高的挥发诱导浓度梯度和随后的扩散通量，观察到略微较高的质量去除速率。一旦浓度降低，就会出现类似的拖尾效应。
