School of Sustainable Engineering and the Built Environment, Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, Arizona 85287, USA.
Environ Sci Technol. 2013 Feb 19;47(4):1977-84. doi: 10.1021/es3045532. Epub 2013 Feb 8.
A proof-of-concept study was conducted to evaluate an alternative to traditional extraction-based subslab vapor mitigation systems at sites with petroleum hydrocarbon and/or methane vapor impact concerns. The system utilizes the slow delivery of air beneath a foundation to attenuate vapor migration to the building via aerobic biodegradation. The study was conducted at a site having elevated hydrocarbon plus methane and depleted O(2) vapor concentrations (160 mg/L and <1% v/v, respectively) beneath a building having a 195 m(2) footprint and a basement extending 1.5 m below ground surface (BGS). Nonaqueous phase liquid (NAPL)-impacted soils, first encountered at about 7.6 to 9.1 m BGS, were the source of hydrocarbon and methane vapors, with the latter being generated by anaerobic methanagenesis of the former. O(2) concentrations beneath and around the building were monitored prior to and during air injection through a horizontal well installed about 1.5 m beneath the foundation. The air injection rate was increased from 1 to 5 to 10 L/min, with each held steady until the O(2) distribution stabilized (46-60 d). The 10 L/min flow rate achieved >5% v/v soil gas O(2) concentrations beneath the foundation and spanning a 1.5 m vertical interval. It was within 3× of the pretest stoichiometric requirement estimate of 3.8 L/min. This resulted in reductions in subslab hydrocarbon plus methane concentrations from 80 to <0.01 mg/L and benzene, toluene, ethylbenzene, and xylenes (BTEX) reductions to below detection limits (0.5-0.74 ppb(v)). This air injection rate is <1% of flows for typical extraction-based mitigation systems.
进行了一项概念验证研究，以评估替代传统基于提取的地基下蒸汽缓解系统的方法，该系统用于解决存在石油碳氢化合物和/或甲烷蒸汽影响问题的地点。该系统利用在基础下方缓慢输送空气，通过有氧生物降解来衰减蒸汽迁移到建筑物的过程。该研究在一个地点进行，该地点的建筑物下方存在升高的烃类和甲烷以及耗尽的氧气（O2）蒸汽浓度（分别为 160mg/L 和<1%v/v），该建筑物的占地面积为 195m2，地下室延伸至地面以下 1.5m（BGS）。非水相液体（NAPL）污染的土壤，首先在约 7.6 至 9.1mBGS 处遇到，是烃类和甲烷蒸汽的来源，后者由前者的厌氧甲烷生成生成。在通过安装在基础下方约 1.5m 处的水平井注入空气之前和期间，监测建筑物下方和周围的 O2 浓度。空气注入率从 1 增加到 5 再增加到 10L/min，每次稳定注入，直到 O2 分布稳定（46-60d）。10L/min 的流速在基础下方和跨越 1.5m 垂直间隔处实现了>5%v/v 的土壤气体 O2 浓度。它接近 3×预测试的化学计量要求估计值 3.8L/min。这导致地基下的烃类和甲烷浓度从 80 减少到<0.01mg/L，苯、甲苯、乙苯和二甲苯（BTEX）减少到检测限以下（0.5-0.74ppb（v））。该空气注入速率<典型基于提取的缓解系统的流量的 1%。
