Unravelling Sources and In situ Processes of Contaminant Remediation Using Multi-element CSIA



Compound-specific isotope analysis (CSIA) is a powerful tool that can be used to gain insight into the processes affecting contaminant concentrations in the subsurface using the ratio of heavy to light isotopes of an element (isotopic composition) in contaminant molecules. The insight provided by CSIA has made it an asset to conceptual site models, particularly at complex sites with multiple controls on contaminant concentrations. CSIA can be applied to differentiate between contaminant sources, to evaluate the presence, extent, and rate of contaminant degradation, and to investigate the relevant mechanisms of degradation present at field sites. Recently, there has been an increase in the application of dual-isotope analysis – where the isotopic composition of multiple elements within a contaminant molecule are measured and plotted on a dual-isotope plot, producing a linear relationship with a calculated slope, lambda (Λ). A dual-isotope plot can be used to infer mechanisms of contaminant degradation, which can facilitate optimization of contaminant degradation at field sites. This mechanistic insight is derived from comparing Λ values from the field to those calculated in controlled laboratory studies. Thus, accurate interpretations are based on accurate methods to calculate and differentiate Λ values. Despite the increasing popularity of the dual-isotope approach, the methods to calculate and compare Λ values has been underdeveloped in the literature to date. In this talk, we will discuss the factors that affect the accuracy of interpretations of Λ and provide recommendations to practitioners applying the dual-isotope approach. Additionally, we will discuss a case study where CSIA was used for source differentiation and to evaluate contaminant degradation at a complex field site.

The Presenters:

Elizabeth Phillips
Liz is a third year PhD student in the Department of Earth Sciences at the University of Toronto. She uses stable isotopes to investigate the reaction mechanisms that microbes use to break down contaminants in groundwater, with hopes to use this knowledge to optimize these processes. This research is funded through NSERC and has previously been funded through an Ontario Graduate Scholarship (OGS). Additionally, Liz is active in different outreach activities that encourage science literacy and science communication and is the program coordinator for the University of Toronto Chapter of Hydrogeologists Without Borders (HWB).

Barbara Sherwood Lollar
Dr. Barbara Sherwood Lollar, Companion of the Order of Canada, FRS, FRSC, is a University Professor in Earth Sciences at the University of Toronto. She is a Canada Research Chair in Isotopes of the Earth and Environment, and Dr. Norman Keevil Chair. She is Past-President of the Geochemical Society and Co-Director of the CIFAR program Earth 4D – Subsurface Science and Exploration. In 2015 she was named a Fellow of the American Geophysical Union and in 2019, a Fellow of the Geochemical Society and European Association of Geochemistry.

Prof. Sherwood Lollar has published on stable isotope geochemistry and hydrogeology, the fate of carbon-bearing fluids and gases such as CO2, CH4 and H2 in ancient fracture waters in the Earth’s crust, deep subsurface microbiology, and the remediation of surface drinking water supplies. She has been a recipient of many academic awards including the 2012 Eni Award for Protection of the Environment, 2012 Geological Society of America Geomicrobiology and Geobiology Prize, 2014 International Helmholtz Fellowship, the 2016 NSERC John Polanyi Award, 2016 Bancroft Award for the Royal Society of Canada, 2018 Logan Medal of the Geological Association of Canada, the 2019 Herzberg Gold Medal for Canada, and the 2019 C.C. Patterson Award in environmental geochemistry.

Prof. Sherwood Lollar has served on many advisory boards including NSERC Council, the United States National Academy of Sciences Space Studies Board, the Honors and Recognition Committee for the American Geophysical Union, and is currently Director of the Earth, Atmosphere and Ocean Sciences Division of the Royal Society of Canada. She was Chair of the 2018 United States National Academy of Sciences “Strategy for Astrobiology and the Search for Life in the Universe” and is a member of the NAS Space Studies Board (2016-2020).

Sandra Dworatzek
Sandra is a Principal at SiREM, which maintains state-of-the-art treatability, molecular testing and bioaugmentation culture growth facilities. She provides technical oversight of laboratory treatability studies and the development and scaleup of new bioaugmentation cultures, including novel cultures for 1,4-dioxane bioremediation.