Compound specific isotope analysis in hydrogeology

Here, we review the contributions of Professor Barbara Sherwood Lollar to Compound Specific Isotope Analysis (CSIA) in contaminant hydrogeology and envi-ronmental chemistry. We first discuss the seminal work by Professor Sherwood Lollar's lab on establishing CSIA as a quantitative tool for contaminant (bio) transformation at contaminated groundwater sites. We describe the critical research by her lab in the development and validation of sample collection techniques, single-and multi-element CSIA, and isotope data evaluation for reliable interpretations. We highlight the contributions of Professor Sherwood Lollar's lab towards the development of best practices for the successful application of CSIA by industry to demonstrate the occurrence of (bio)transformation, identify (bio)trans-formation mechanisms, quantify the extent and rate of degradation and differentiate among potential contaminant sources. We then explore Professor Sherwood Lollar's applications of CSIA to hydrogeology of the deep subsurface and the fast widening of the field to new environments (e.g., sediments), contaminants (e.g., chlorofluorocarbons, pesticides), and systems (e.g., plant, enzymes).