文章基本信息

标题：Methane Transport during a Controlled Release in the Vadose Zone
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作者：Mark Felice ; Nick de Sieyes ; Juan Peng 等
期刊名称：Vadose Zone Journal
电子版ISSN：1539-1663
出版年度：2018
卷号：17
期号：1
页码：1-10
DOI：10.2136/vzj2018.02.0028
出版社：Soil Science Society of America, Inc.
摘要：Core Ideas Vadose zone CH 4 migration was densely monitored during a controlled‐release scenario. Soil moisture strongly influenced vadose zone CH 4 fate and CH 4 oxidation. Soil CH 4 fate appears primarily controlled by biological CH 4 oxidation. Shallow, small‐rate releases of ethanol‐blended fuels from underground storage tanks (USTs) may be quite common and result in subsurface CH 4 generation. However, vadose zone transport of CH 4 generated from these fuel releases is poorly understood, despite the potential to promote vapor intrusion or create explosion hazards. In this study, we simulated shallow CH 4 generation with a controlled subsurface CH 4 release from July 2014 to February 2015 to characterize subsurface CH 4 migration and surface emissions and to determine environmental controls on CH 4 fate and transport. July 2014 through November 2014 was an extended period of drought followed by precipitation during December 2014. Throughout the experiment, under varied CH 4 injection rates, CH 4 formed a radially symmetrical plume around the injection point. Surface efflux during the drought period of the experiment was relatively high and stable, with approximately 10 to 11 and 34 to 52% of injected CH 4 reaching the ground surface during the low‐ and high‐rate injections, respectively. Following the period of precipitation and increased soil moisture, efflux dropped and stabilized at approximately 1% of injected CH 4 , even as soil moisture began to decrease again. Tracer and inhibitor experiments and estimates of soil diffusivity suggest that microbial CH 4 oxidation was responsible for the observed drop in efflux. The decrease in efflux only after soil moisture increased suggests a strong environmental control over the transport and oxidation of vadose zone CH 4 .
关键词：BGS; below ground surface; DFE; difluoroethane; PVC; polyvinyl chloride; TDR; time domain reflectometry; UST; underground storage tank.