Identifying, Understanding and Quantifying Contaminant Amplification Processes

Séminaire de F. Wania le Mercredi 19 Juin 2019 à 10h en salle Lliboutry, Bât. Glaciologie

Title : Identifying, Understanding and Quantifying Contaminant Amplification Processes

Frank Wania
Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario, Canada M1C 1A4

Abstract :
Because the “dose makes the poison”, environmental chemists try to identify the locations of high contaminant concentrations and thus elevated exposure. Under most circumstances, concentrations decline with increasing distance from source because of dilution and degradation. However, contaminant amplification can counter and on occasion completely reverse the effect of dilution. It is clearly imperative to identify, understand and quantify contaminant amplification processes, because of their potential to give rise to unexpectedly high exposure. The fundamental mechanisms of contaminant amplification have been identified and can be related to equilibrium partitioning (“solvent switching”), rapid phase change (“solvent depletion”), and kinetic phenomena (“traps”). This will be illustrated using three prominent examples of contaminant amplification, namely mountain cold-trapping, polar cold-trapping, and gastrointestinal biomagnification. Numerical models of contaminant amplification have an important role to play. Once confirmation of their ability to reproduce observations has established a satisfactory understanding of the underlying amplification processes, it is possible to use them to compare chemicals and “systems” (mountains, worlds with different climates, organisms, food chains, human individuals and populations) in terms of their amplification capabilities. By being able to constrain the chemical property combinations that allow for trapping in mountains, accumulation in polar regions and biomagnification in human food chains, we can (i) identify among the myriad of chemicals in commerce those having problematic amplification properties, and (ii) design new products and processes in such a way to avoid the use of chemicals with such properties in the future.