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Barbara Sherwood Lollar

Director, Stable Isotope Laboratory
Professor, Department of Geology (adjunct Chemistry)
St. George Campus, University of Toronto

Research in contaminant hydrogeology

 Sherwood Lollar image

My research group has played a pioneering role in the development of a new field of stable isotope research - the application of compound specific isotope analysis (CSIA) to contaminant hydrogeology. Contamination of groundwater resources with petroleum hydrocarbons and chlorinated solvents is widespread in both rural and urban settings and represents one of the most urgent challenges facing environmental science. My research group is one of the first to have successfully developed and applied techniques for using compound specific stable carbon isotopes to investigate controls on the origin of these low level dissolved priority pollutants and on their transport and fate in the subsurface Current research deals with the following key questions related to the subsurface distribution and behaviour of organic compounds in groundwater. Can isotopes be used to differentiate and quantify sources at sites where a number of discrete spills may contribute to contamination? To what extent is isotopic fractionation associated with relevant subsurface processes that control contaminant fate and attenuation i.e. volatilization, adsorption, biodegradation, and abiotically-mediated degradation? In addition, we aim to refine the ability of compound specific stable isotope techniques not only to identify the effects of degradation but to provide a novel means to quantitatively evaluate the effectiveness of remediation approaches to groundwater cleanup.

Research on the origin of hydrocarbon gases in the subsurface

We reported the first direct evidence for inorganic synthesis of methane and higher hydrocarbons in crystalline rocks of the Canadian Shield based on the carbon and hydrogen isotopic values of C 1 -C 4 alkanes in a suite of 11 samples from Kidd Creek Mine, Timmins, Ontario, Canada. This paper was highlighted on the April 4, 2002 cover of Nature. It is generally recognized that the first pre-biotic organic molecules on earth and elsewhere in the solar system must have been formed by abiogenic reactions. To date it had been largely assumed that after the evolution of life on earth, biologically mediated reactions overprinted evidence of this pre-biotic abiogenic history. My research is the first indication that abiogenic reactions that contributed to the formation of primary organic molecules on the early earth continued to play a significant role in the production of hydrocarbons in the Precambrian rocks of the earth’s crust. In addition, one of the most exciting scientific discoveries of the past decade has been the discovery that microbial life exists in the subsurface at depths hitherto unanticipated - the so-called “deep biosphere”. Recent work provided a framework for quantifying the relative contributions of microbial versus geologic sources of methane to the terrestrial deep subsurface and to Mars - a topic that earned the latter paper the cover of Astrobiology in 2006.

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