Uncertainties on atmospheric aerosol particle emission and deposition fluxes: observation and needs to improve quantification

English Abstract:

Assessing, understanding and predicting the impact of accidental or chronic releases of particulate pollutants (chemical, radioactive, biologic) in ecosystems is a major issue in the context of risk management for the population. In addition, aerosol particles play an important role in global warming by reducing the action of greenhouse gas emissions. Particle concentrations in the atmosphere depend on the particle sources (primary and secondary), particle evolution (coagulation), and the dry and wet deposition processes. Predictive emission, transfer and deposition models, developed and improved from in situ flux measurements, are important tools to better protect population and to understand dynamics of aerosol in the surface layer. For now, experimental data are scarce and gaps between measurements and model results, and between model predictions, are usually huge. For examples, there is several orders of magnitude discrepancy between scavenging coefficients or dry deposition velocities. These uncertainties are due to the lack of accurate experimental data in function of specific parameters such as particle size and atmospheric turbulence. Although there have been recent important progresses in experimental and numerical studies, there remains many challenges before achieving this goal. For example, systematic high frequency measurements of particle concentrations combined with spectral corrections, or use of appropriate surrogates in deposition particle tracing methods, would allow a better quantification of the dry deposition fluxes. It is proposed here to review experimental and data processing techniques used in the environment to estimate aerosol particles fluxes and to discuss some improvements to methodologies for a better quantification. This topic is also being addressed by an international working group whose common goal is to publish recommendations for environmental particle fluxes quantification.