Tech Focus: Compound-Specific Isotope Analysis
Having difficulty determining a contaminant’s source and age? Searching for a way to make sense of commingled plumes when the fate and transport analysis isn’t painting a clear picture? Look no further than Compound-Specific Isotope Analysis (CSIA), an Environmental Molecular Diagnostic (EMD) tool that can be used to answer these difficult questions. CSIA can be used on a range of sites impacted by volatile organic compounds. This includes sites with complex hydrogeology and large commingled plumes, sites needing assessment of contaminant behavior and degradation, and even simpler sites with potential impacts from unknown sources where a standard background study is not feasible due to upgradient, off-site access constraints. Here at Langan, we have experience using CSIA and other EMD tools to design and monitor successful remedial actions, petition for site closure, and support litigation regarding apportionment of environmental liabilities.
The CSIA method works by measuring the amount of stable isotopes of carbon, hydrogen, or chlorine in a specific contaminant such as trichloroethylene or tetrachloroethene. The ratios of these elemental isotopes are unique to an individual contaminant at a site and can change in relatively predictable ways depending on the degradation mechanisms occurring at the site. For example, ratios would remain the same if a contaminant was only affected by an abiotic process, such as dispersion, and would change in a more predictable way if undergoing aerobic biodegradation. Different sources are also likely to have different ratios, allowing for a better understanding of contributions from various responsible parties to commingled plumes.
CSIA is just one tool in an environmental professional’s toolkit. It is best when implemented in accordance with interpretation of traditional chemical, geochemical, and hydrogeological data and/or other EMDs. Together, CSIA and other EMDs provide multiple lines of evidence supporting site and remedial investigations. Implementation of these tools requires a skilled and experienced professional to execute the investigation and interpret the results.
Langan played an active role in the Interstate Technology and Regulatory Council that developed a robust internet-based training program and technical guidance document on the use of EMDs, including CSIA, and remains up-to-date on technological advances in this field.
About Ryan Andersen
Ryan Andersen is a Senior Project Manager who has been with Langan since 2005. His practice involves site investigations, remedial action assessments and site remediation, brownfield redevelopment support, waste management, and due diligence support under multiple state and federal regulatory programs. Most recently his practice has focused on strategizing, investigating, and remediating complex emerging contaminant issues arising at existing sites.