Août 2016

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1. Candidatures de scientifiques francophones et de scientifiques féminines de haut niveau

2. The work of the Stable Isotope Laboratory at the University of Toronto

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Andres MiallPériode tranquille, l’été est la saison où la plupart des membres sont probablement en train de se rattraper dans leur travail au laboratoire de recherche, de recueillir des données sur le terrain ou de prendre des vacances. Je suis donc reconnaissant à ma collègue de l’Université de Toronto, Barbara Sherwood Lollar, pour la contribution qu’elle a apportée. Sa carrière, remarquable, a récemment été mise en évidence quand son nom a paru dans la liste des compagnons de l’Ordre du Canada publiée le 1er juillet. Mme Sherwood Lollar s’est vu décerner de nombreux prix pour son travail dans le domaine de l’environnement. Tout récemment, le CRSNG lui a remis le prestigieux Prix John C. Polanyi pour ses recherches d’avant garde sur l’eau vieille d’un milliard d’années et les indices que celle-ci pourrait fournir concernant les anciennes formes de vie sur Terre et sur Mars. Portant le nom du lauréat d'un prix Nobel de l’Université de Toronto, ce prix rend hommage à un chercheur ou à une équipe de chercheurs dont les travaux menés au Canada sont à l'origine d'une percée remarquable réalisée récemment en sciences naturelles ou en génie.

Il s’agit du deuxième d’une série de messages que j’ai voulu créer pour célébrer la réussite aux échelons national et international de membres qui, dans leurs réalisations, se surpassent et se méritent une reconnaissance nationale et internationale exceptionnelle pour leur travail.

Andrew D. Miall, FRSC

1. Candidatures de scientifiques francophones et de scientifiques féminines de haut niveau

Chers/chères membres de l’Académie des sciences

Jacques DeromeLes francophones et les femmes sont en petits nombres au sein de l’Académie des sciences du Canada, une situation que nous aimerions vivement améliorer. Les statistiques démontrent que la source du déséquilibre est liée au nombre de candidatures, beaucoup trop faible, et non au taux de succès. Nous venons donc solliciter votre aide pour faire en sorte que plus de scientifiques francophones et de femmes soient proposés comme nouveaux membres de l’Académie. C’est la troisième année que nous lançons cet appel et nous avons constaté avec bonheur que, coïncidence ou pas, le nombre de francophones et de femmes élus à l’Académie des sciences en 2015 et 2016 a augmenté de façon marquée. En 2016, 20% et 21% des nouveaux membres de notre Académie sont des francophones et des femmes, respectivement, ce qui nous encourage à continuer nos efforts. 

Nous invitons donc tous les membres de l’Académie des sciences à soumettre des candidatures de collègues dont les réalisations scientifiques méritent d’être reconnues, et de s’assurer que les noms de scientifiques francophones et de scientifiques féminines ne soient pas oubliés. Bien sûr nous sollicitons toutes les candidatures de haut niveau scientifique, indépendamment de toute autre considération.

Finalement, notre invitation à soumettre plus de candidatures, en particulier francophones et féminines, s’applique aussi aux prix et médailles offerts par l’Académie. À noter que la Médaille Willet G. Miller, qui avait été suspendue en 2012, est offerte à nouveau, et maintenant pour toutes les disciplines de la division des sciences de la terre, de l’océan et de l’atmosphère  –  les nominations sont invitées en grand nombre.  Il y a probablement dans votre entourages des collègues qui feraient des candidat(e)s de tout premier rang – que diriez-vous de soumettre leurs candidatures?

Les procédures à suivre pour soumettre des candidatures seront disponibles sur le site web de la Société à l’adresse suivante à compter du 1er septembre : http://rsc-src.ca/fr/membres/médailles-distinctions 

Nous comptons sur votre collaboration et vous en remercions.

Jamal Deen, Président de l'Académie des sciences
Jacques Derome, Secrétaire de l'Académie des sciences

2. The work of the Stable Isotope Laboratory at the University of Toronto

Barbara Sherwood LollarThe Stable Isotope Laboratory for research into the isotope geochemistry of the Earth and the Environment was founded in 1992 when I took up a professorial position at the University of Toronto. Following the twin themes of carbon cycling and the interface between the carbon cycle and water, our research program had the good luck of timing and the blessing of a vision of applying the new generation of continuous flow stable isotope mass spectrometry to the mounting challenges facing scientists and society around the issues of energy resources, water resources and the environment. From the discovery of “billion year old water” deep beneath the Canadian Shield, to pioneering developments of new knowledge and techniques in “compound specific isotope analysis” (CSIA) to investigate remediation of groundwater resources, these dual themes drive our students and postdoctoral research investigations to the present day.

Novel Approaches for Remediation of Groundwater Resources

Hydrocarbon contaminants, including petroleum hydrocarbons, chlorinated solvents and fuel additives, are ubiquitous at both urban and rural sites, and at both large scale facilities (e.g. industry, airports, railways) and smaller sites related to local neighbourhood operations (e.g. garages, machine shops, dry cleaners). While the disposal of such compounds is now carefully regulated, there is a legacy worldwide of impacted soil and groundwater from the history of our past use and practices. Our research at the University of Toronto helped to established the scientific principles involved in using compound specific stable carbon isotope signatures, rather than just concentration levels of contaminants, to determine the fate of hydrocarbon contaminants in groundwater - and particularly, the effectiveness of proposed environmental clean-up strategies.

Specifically, compound specific isotope analysis, or CSIA, refers to determination of the stable carbon isotope signature (13C/12C ratio or 13C value) for organic contaminants. Through careful laboratory and field experimentation our research team demonstrated that for many hydrocarbon priority pollutants, large shifts in the isotopic signatures (fractionation) of both parent compounds and their breakdown products provide a dramatic indicator of both biotic and abiotic transformation reactions involved in degradation (clean-up) at field sites. At the most fundamental level, the kinetic isotope fractionation effect (resulting in a change in the 13C/12C ratio for a given compound) is due to the greater activation energy for reactions involving a bond containing the heavy isotope (13C) compared to a bond containing the lighter isotope (12C). This results in molecules with the light isotope typically having a faster reaction rate relative to those containing a heavy (13C) containing molecule. Transformation reactions (whether microbially or chemically catalyzed) typically showed much more significant fractionation for carbon isotopes than processes that involved strictly phase changes (dissolution, volatilization) or mass redistribution due to transport or sorption, but not the breaking of bonds.

These results had profound implications as they introduced the concept of using natural abundance isotope signatures of individual environmental contaminants to identify if degradation was occurring at field sites by distinguishing between decreases in concentration due to actual transformation (clean-up) versus concentration decreases related simply to dispersal of contaminants further into the environment. The latter is undesirable due to the high toxicity or environmental/health impacts of many for these compounds even at low concentrations in the environment.

A second important aspect and corollary of these results is that the degree of fractionation observed during transformation of a compound is controlled by the specifics of the reaction mechanisms, or which bonds are broken. In situ degradation remediation schemes involving both biotic and abiotic processes are a major focus of R&D on site remediation for organic contaminants. Contaminant remediation schemes designed to enhance in situ degradation need to consider, among other key issues, the mechanisms by which contaminant transformation occurs and the rate of those reactions. Without that understanding, optimization of remediation operations cannot be easily achieved, and monitoring of performance and predictions of cleanup costs and timelines are risky. Hence the work by our students and postdocs represent not only major scientific advances in our understanding of the use of isotopes to investigate biogeochemistry of the environment, but an important tangible benefit to society – providing evidence for clean-up that is critical to risk assessment, optimization of site remediation strategies, cost effective clean-up, and public and regulatory confidence in remediation.

“Billion year old water” and the deep subsurface biosphere

Working in the gold mines of South Africa with colleagues from Princeton, Potsdam, and the University of Free State, in 2011, through integrating stable isotopes of waters and gases (CHON) with conservative noble gas analyses, we made the exciting discovery that while the residence of the bulk of the flowing fracture waters found 2.8 km deep below the Earth’s surface was on the order of 25 million years, neon (a conservative element that acts as a tracer of fluid origin) dissolved in the waters was in fact derived from the remnants of 2 billion year old metamorphic fluids. Comparison of our geochemical data for the free gases and fluids to those in fluid inclusions confirmed that in these extremely old, hydrogeologically isolated fractures, leaching of the fluid inclusions is the source of a significant component of the noble gas inventory in the fracture waters. This paper sparked intense interest in how many other deep hydrogeologic systems beneath the continents might also contain elements with provenance on the order of millions or billions of years.
   
An essential next step required determining whether such ancient noble gas components in deep fracture waters were unique to the Kaapval, or a more general phenomenon in Precambrian age rocks worldwide. To address this, I established a collaboration with Chris Ballentine (Oxford), to return to the Canadian Shield and explore the deep mines there in search of ancient fluids and possible microbial communities therein. The results of our initial study on the Canadian Shield at Kidd Creek mine in Timmins Ontario revealed the most radiogenic He, Ne, Ar signatures ever identified in fracture waters at 2.7 km depth. These corresponded to the oldest bulk residence times ever measured for groundwater (with mean residence times > 1 Ga).  Although ancient rocks are known to trap microscopic quantities of gas and fluid from the time of their formation in the early Earth (fluid inclusions), this was the first discovery of water flowing (at rates of liters per minute) of such immense antiquity. Literally bubbling out of fractures deep in the planet’s oldest rocks, this discovery revealed a whole new source of samples retaining information about fluids and gases from the early Earth.

Our students and postdocs continue their work exploring this new dimension of the Earth’s deep hydrosphere, investigating the carbon source and role of microbial subsurface ecosystems in the deep carbon cycle, identifying the electron donors and acceptors sustaining life in these deep environments, and exploring a range of settings across the world’s oldest rocks to determine the breadth, depth and extent of this ancient hydrosphere. Integrating hydrogen and noble gas data from more than 250 samples at >30 sites worldwide, a recent paper demonstrated how chemical reactions (radiolysis and serpentinization) produce substantial quantities of hydrogen, doubling estimates of global production from these processes - a quantum change in our understanding of the total volume of Earth’s crust that may be habitable for microbial ecosystems. Since Precambrian rocks make up >70% of the Earth’s crust, we likens these terrains to a “sleeping giant” - a huge area that has now been discovered to be a source of possible energy for life. Since major sections of the Mars crust is a similar age and mineralogy to the Precambrian continents of Earth, this discovery provides an insight into possible mechanisms of hydrogen and methane production on Mars, and a model of how chemical energy might support life in ancient rocks. The discoveries have applied significance as well, informing our understanding of ancient rocks that have in some locations been proposed as sites of low level and high level nuclear waste disposal, and providing a new source of information on fluids participating in ore deposition and mineral formation processes.

Barbara Sherwood Lollar, FRSC