Description

Compound-Specific Isotope Analysis (CSIA) is a powerful environmental forensics and performance-monitoring tool used to evaluate contaminant sources, distinguish degradation mechanisms, and assess the effectiveness of remediation treatments. This Tech Brief explains how CSIA supports plume forensics, monitored natural attenuation (MNA), and verification of remediation performance at petroleum and chlorinated solvent sites.

This technical brief provides an applied overview of Compound-Specific Isotope Analysis (CSIA) as a diagnostic tool for environmental forensics, remediation performance monitoring, and risk-based decision-making at contaminated sites. CSIA evaluates changes in stable isotope ratios (e.g., δ¹³C, δ²H, δ³⁷Cl) of individual contaminants to distinguish between dilution and true contaminant mass destruction, identify degradation pathways, and assess remediation effectiveness independent of concentration data.

The document explains how CSIA is used to:

• Differentiate abiotic versus biotic degradation mechanisms

• Identify contaminant sources and plume commingling

• Quantify biodegradation rates and validate monitored natural attenuation (MNA)

• Evaluate performance of remedies such as ISCO, ISCR, permeable reactive barriers, air sparging/SVE, and reductive dechlorination

Illustrated examples show how isotope trends evolve spatially and temporally in groundwater systems, providing multiple lines of evidence for fate and transport interpretations. The brief also highlights the integration of CSIA with mass flux measurements—including passive flux samplers—to support plume modeling, receptor risk assessment, and optimization of remediation strategies.

This reference is intended for environmental consultants, regulators, and remediation practitioners seeking defensible tools to support site characterization, remedy selection, and performance verification. 

Applying CSIA to your site:

Tersus Environmental provides technical support for CSIA study design, sampling strategies, data interpretation, and integration with performance monitoring and remedial decision frameworks.