Environmental Heavy Stable Isotope Research

Advances in the field of “non-traditional” stable isotope research, including Multi-collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS) allow the analysis of the isotopic signatures of heavy elements. My research includes the development of new and novel methods and applications for heavy stable and radiogenic isotopes. My research aims to characterize the isotopic variation among metal sources and to quantify the extent to which reactions (physical, chemical and biological) cause heavy metal stable isotope fractionation, with the goal of developing these isotope systems as tools for source and process identification.


Tracing of smelting emissions using Cd, Zn, and Pb isotopes

This research uses a combination of Cd, Zn, and Pb isotopes to trace the impact of smelting emissions. We have demonstrated that Cd and Zn isotopes are fractionated during metallurgical processes and that they have the potential to trace their distributions in the environment. In contrast, Pb isotopes are used to identify the ores, with unique radiogenic signatures, processed by the smelter.


Development of uranium (U) isotope fractionation as an indicator of U immobilization by U(VI) reduction to U(IV)


This research investigates the use of U isotopic composition as a tool for evaluating U(VI) reduction to U(IV) by measuring the 238U/235U of groundwaters from a U contaminated aquifer at a former uranium mill site in Rifle, CO. We have demonstrated that significant U isotopic fractionation accompanies U(VI) reduction during bioremediation and thus, that U isotopes provide a powerful tool for quantifying the extent of U(VI) reduction to U(IV) and thus, immobilization.


Development of cadmium (Cd) and zinc (Zn) isotopes as tracers of metal sources and environmental fate

This research seeks to improve our understanding of biogeochemical cycling of Cd and Zn and their isotopes. This requires characterization of their sources, transformations and fate in the environment. Stable isotopes are fractionated during physical, chemical and biological reactions. Ultimately, this research serves to develop heavy stable isotopes as tools for gaining process information in modern oceans and for reconstructing past conditions.


Tracing Cd, Zn and lead (Pb) sources in bivalves (oysters and mussels) from Canada, the USA and France


In contrast to efforts focused on the use of metal concentrations, which are limited in their ability to assess metal sources, I used Cd, Zn and Pb isotope ratios to trace the source of these metals in bivalve tissues. I used this technique to determine that despite relatively high Cd levels in British Columbian bivalves, Cd in their tissues is primarily natural, likely originating from the upwelling of nutrient-rich (and Cd-rich) waters along that coast. In contrast, I identified Cd in bivalves from France and the USA East Coast as primarily anthropogenic.

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Environmental and Isotope Geochemistry