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

Abstract

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 surfaces. 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 experimental 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 addition, 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 advantages of the SVC method were its low detection limits, lack of required auxiliary equipment, and ability to obtain realtime estimates of fugitive VOC emission rates. IMPLICATIONSThis research will aid in achieving both hazardous air pollutant and ozone precursor goals set by the U.S. Environmental Protection Agency and state regulatory agencies by providing an accurate, rugged, and easy to use method of monitoring air emissions of volatile organic compounds and other gases from soil surfaces. The method has several advantages over methods of monitoring fugitive emissions from soil surfaces, including faster sampling time, lower detection limits, and the ability to obtain real-time results without cryogenic or sorbent tube trapping.

Air Emission Flux from Contaminated Dredged Materials Stored in a Pilot-Scale Confined Disposal Facility

“…This was the observation from the model prediction as well. It is important to point out that the sediment core analysis provides an alternate way of obtaining the long-term steady state flux from the product of the effective diffusivity and the slope of the concentration profile, as suggested recently by Ergas et al 28 There was no evidence of significant biodegradation or leaching from the CDF. Samples from the control cells were withdrawn after ~500 hr, and the loading of phenanthrene was found to be 21 and 28 mg/kg for the cells with the biocide and without the biocide, respectively.…”