Isabelle lessard
MScA candidate
(Chemical Engineering Department - cole Polytechnique de Montral)
isabelle-2.lessard@polymtl.ca
Expertise :
- Terrestrial ecotoxicology
- Soil biochemistry and microbiology, enzymatic activity
- Environmental chemistry and metal speciation
- Statistical analysis of biological data
Start: January 2007
Director: Louise Deschênes
Co-director: Réjean Samson and Sébastien Sauvé
Research project:
Elaboration of a dose-response curve based on the enzymatic activity of metal-contaminated soils
Project summary:
Life cycle impact assessment (LCIA) is an environmental tool based on risk assessment methodology. Substance emission impacts are modeled in a life cycle assessment (LCA). To evaluate the terrestrial ecotoxic impact of metals, the LCIA model IMPACT 2002 generates a characterization factor (CF) based on fate, exposure and effect factors. The effect factor is based onthe geometric mean of toxicity thresholds obtained with ecotoxicological tests; these threshold values must come from at least three different phyla to be effective.
However, no sufficient data is available to cover the trophic levels needed. To bypass this problem, terrestrial data are extrapolated from aquatic data by multiplying them using a soil-water partition coefficient (kD). In a metallic contamination context, these computations could be distorded because kD is not metallo-specific and depends on soil physicochemical properties. In addition, LCIA models consider total metal concentration as toxic, but only a fraction actually is, mainly that associated to free ions.
Furthermore, almost all terrestrial ecotoxicological tests are done in spiked samples, but aging of metallic contamination in field soils generally reduces their toxicity and it is difficult to recreate this natural field-process in laboratory-contaminated soils. Finally, standard operational procedures of enzymatic analyses use a buffer solution to fix optimal pH during incubation time. In a metallic contamination context, this practice is challenged since the buffer could change metal speciation and therefore, the resulting toxicity. There is a pressing need to generate terrestrial data from a new phylum type and to include metal speciation and aging in the risk assessment of metals and also LCIA.
This study aims to develop a dose-response curve taking into account metal speciation and based on enzymatic activity of metal-contaminated field soils. Since enzymes are mainly secreted by micro-organisms, a seldom-used phylum in ecotoxicology, soil enzymatic analysis could be an interesting way to predict contaminant toxicity. This study also attempts to identify soil physicochemical properties which influence metal toxicity, and to put recommendations forward on using a buffer solution when evaluating metal toxicity by enzymatic assays.
Publications/presentations:
Lessard, I Bécaert, V. Sauvé, S, Samson, R. Deschênes, L (2008). Elaboration of a Dose-Response Relationship Based on the Enzymatic Stability of Zinc-Contaminated Soils. Affiche présentée au SETAC Europe 18th Annual Meeting. Varsovie (Pologne). 26 au 29 mai 2008.
Career path:
M.Sc.A, chemical engineering, environment
École Polytechnique de Montréal, en cours
B.Ing., chemical engineering, environment
École Polytechnique de Montréal, 2006
Student exchange (4 month)
University of Alberta, Edmonton, 2005
Industrial Internship (8 month), Dry film process and electroplating
Viasystems Canada, Kirkland, 2004