Accession Number : ADA606285
Title : Use of Compound-Specific Stable Isotope Analysis to Distinguish Between Vapor Intrusion and Indoor Sources of VOCs
Descriptive Note : Final rept.
Corporate Author : GSI ENVIRONMENTAL INC HOUSTON TX
Personal Author(s) : Beckley, Lila ; McHugh, Thomas ; Kuder, Tomasz ; Philp, R P
Report Date : Nov 2013
Pagination or Media Count : 414
Abstract : Indoor sources of VOCs are ubiquitous, resulting in detectable concentrations in indoor air, often at levels exceeding regulatory screening criteria. At corrective actions sites with potential vapor intrusion concerns, the presence of indoor VOC sources significantly complicates the exposure pathway evaluation. Because of these indoor sources, the detection of a site-related VOC in a potentially affected building does not necessarily indicate a vapor intrusion impact. However, because conventional investigation methods often do not clearly identify the source of VOCs, additional rounds of sampling are commonly required. The overall goal of this demonstration was to validate use of compound-specific stable isotope analysis (CSIA) to distinguish between vapor intrusion and indoor sources of VOCs. As part of this project, a step-by-step protocol has been developed which can be used to provide an independent line of evidence to determine whether or not buildings are impacted by vapor intrusion. Many elements, such as carbon, occur as different isotope species, differing in their number of neutrons present in the nucleus. For example, 12C, with 6 neutrons, is the most abundant form of carbon. 13C, with 7 neutrons, makes up a small fraction (1%) of the carbon in the environment. Isotopic ratios (13C/12C) of a specific compound (e.g., TCE) can vary as a result of differences in their source material or compound synthesis or due to transformation in the environment (USEPA, 2008). Differences in the isotopic ratio measured in organic contaminants present in environmental samples can be used to i) distinguish between different sources of the contaminants and ii) understand biodegradation and other transformation processes occurring in the environment. While CSIA has been applied to groundwater investigations, its applicability to vapor intrusion assessments has only recently been explored (e.g., McHugh et al., 2011).
Descriptors : *ORGANIC COMPOUNDS , *STABLE ISOTOPES , *VAPORS , COST ANALYSIS , DATA ACQUISITION , FIELD TESTS , GEOLOGY , HYDROGEOLOGY , INDOOR AIR POLLUTION , INTRUSION , SAMPLING , SOURCES
Subject Categories : Organic Chemistry
Air Pollution and Control
Distribution Statement : APPROVED FOR PUBLIC RELEASE