National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Jilin University, Changchun,130021, China; Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun,130021, China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, China.
National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Jilin University, Changchun,130021, China; Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun,130021, China.
J Hazard Mater. 2020 Nov 5;398:122866. doi: 10.1016/j.jhazmat.2020.122866. Epub 2020 May 15.
The decrease of remediation effect during air sparging (AS) remediation in heterogeneous porous media has attracted increasing attention. In this study, an improved light transmission visualization method was used to investigate the air accumulation, migration and flowrate distribution in benzene-contaminated heterogeneous porous media during AS. Experimental results indicated that the benzene removal rate in the porous media was mainly controlled by air flowrate distribution which could be used as a major factor to evaluate the remediation effect. Visualization of air migration showed that air accumulation occurred below the geologic heterogeneous interface when ΔPe > 0 kPa (ΔPe: the air entry pressure difference of the media above and below the interface), and the accumulation thickness and length presented exponential decay increases with increasing ΔPe and air injection rates. Air flowrate was monitored by gas flow sensors, and the flowrate distributions were found as Gaussian distribution when ΔPe ≤ 0 kPa, trapezoidal distribution when 0 <ΔPe< 0.3 kPa and fingered distribution when ΔPe ≥ 0.3 kPa. Fingered distribution of air flowrate resulted in extremely nonuniform benzene removal above the interface and reduced the overall benzene removal rate. These findings reveal the reasons for the poor performance of AS remediation in heterogeneous porous media, leading to a better understanding of the remediation mechanisms in heterogeneous aquifer.
空气注入（AS）修复在非均相多孔介质中修复效果降低的问题引起了越来越多的关注。本研究采用改进的透光率可视化方法，研究了苯污染非均相多孔介质中 AS 过程中的空气积聚、迁移和流速分布。实验结果表明，多孔介质中的苯去除率主要受空气流速分布控制，空气流速分布可作为评估修复效果的主要因素。空气迁移的可视化表明，当 ΔPe > 0 kPa 时（ΔPe：界面上下介质的空气进气压力差），会在地质非均相界面下方发生空气积聚，积聚厚度和长度随 ΔPe 和空气注入速率的增加呈指数增加。通过气体流量传感器监测空气流量，发现当 ΔPe ≤ 0 kPa 时，流量分布呈高斯分布，当 0 <ΔPe< 0.3 kPa 时，呈梯形分布，当 ΔPe ≥ 0.3 kPa 时，呈指状分布。空气流量的指状分布导致界面上方苯去除极不均匀，降低了整体苯去除率。这些发现揭示了 AS 在非均相多孔介质中修复效果不佳的原因，有助于更好地理解非均相含水层的修复机制。
