CASISURF

Aerosols are recognized as a key parameter driving health effects of atmospheric pollution. A certain number of scientific studies clearly point out the limitation of the current regulation on particulate matter (PM) to understand and quantify cause-to-effect relationship between particulate matter (PM) levels and health impacts. In order to improve quantification of their atmospheric impacts, monitoring of aerosol properties must, in the future, be extended to new parameters. Aerosol surface area is one of the most important atmospheric aerosol properties in health effects. However, methods for online measurement of the surface area are not widely available and/or require complex operations. The primary objective of the project is, therefore, to investigate the use of recent advances in spectroscopic techniques for the measurement of aerosol surface area and surface properties and their extension to health issues. Our aim is to develop a technique that enables real time in situ monitoring of the aerosol surface. Understanding the health impacts of aerosols typically requires acute effects to be observed after expose to concentrated number. To achieve such exposures, it is necessary to concentrate the particles by any means to initiate such acute effects. Particle concentrators using virtual impactors are typically used for that purpose. However, they may not be applied to ultrafine particles, as the latter may first have to grow to micrometer sizes (in a supersaturated environment) before being concentrated by the virtual impactors. However all these processes are now know to modify the surface physical state and its chemical composition. As these parameters are believed to be essential factors, governing the particles toxicity, there is real and definite need of tools capable of characterising, at low cost, on-line and in situ the surface of given aerosols. To achieve this goal, we intend to link some surface optical properties to the real aerosol surface. In order to be reproducible, and hence have the potential to be employed under real environmental conditions, this comes along with the requirement of control this surface optical property. We do therefore intend to cover given particles with a monolayer of a (or several) organic compounds that could be used as a tracer for determining surface properties. The main outcome of this project would be the basis of a new tool that would allow the monitoring of the aerosol surface in addition to existing devices monitoring mass and/or number of the particles. Also, an AMS would be made available to the French research community with a broad range of applications and outcomes.