Near Surface Soil Vapor Clusters for Monitoring Emissions of Volatile Organic Compounds from Soils

摘要

The overall objective of this research was to develop and test a method of determining emission rates of volatile organic compounds (VOCs) and other gases from soil sur- faces. Soil vapor clusters (SVCs) were designed as a low dead volume, robust sampling system to obtain vertically resolved profiles of soil gas contaminant concentrations in the near surface zone. The concentration profiles, when combined with a mathematical model of porous media mass transport, were used to calculate the contaminant flux from the soil surface. Initial experiments were conducted using a mesoscale soil remediation system under a range of ex- perimental conditions. Helium was used as a tracer and trichloroethene was used as a model VOC. Flux estimations using the SVCs were within 25 of independent surface flux estimates and were comparable to measurements made using a surface isolation flux chamber (SIFC). In ad- dition, method detection limits for the SVC were an order of magnitude lower than detection limits with the SIFC. Field trials, conducted with the SVCs at a bioventing site, indicated that the SVC method could be easily used in the field to estimate fugitive VOC emission rates. Major advan- tages of the SVC method were its low detection limits, lack of required auxiliary equipment, and ability to obtain real- time estimates of fugitive VOC emission rates.