Isoprene and monoterpenes biogenic emissions in France:: modeling and impact during a regional pollution episode

Biogenic emission of isoprene and monoterpenes are modeled in order to study their impact on regional atmospheric chemistry and pollution in France. First, an emission potential inventory is developed using a fine scale landuse database, forest composition statistics, biometric data and species emission factors. Considering the main emission patterns, the results show consistency with previously published European and global inventories. When downscaling to sub-region of France, this database is likely to provide refined sources distribution, an important issue for regional atmospheric chemistry studies. The temporal evolution of biogenic fluxes with meteorological conditions is calculated on line in the MesoNH-C meso-scale atmospheric chemistry model. Leaf-level algorithms are integrated at the ecosystem scale using sub-grid prognostic surface temperature and canopy shading effects. Finally, ecosystem to landscape integration is performed by aggregating biogenic fluxes at the model grid cell scale. Uncertainties associated with these estimations are discussed with respect to different spatial scales. In the second part of the paper, these developments are used to study biogenic emission impacts on regional ozone formation. We focus on a summer pollution event over Paris and northern France, documented during the ESQUIF experiment. The introduction of biogenic fluxes led to an increase in simulated surface ozone concentrations, reaching 18-30% in the Paris plume and about 20-30% in some rural areas. This impact was mainly due to large biogenic fluxes as well as to the chemical conditions prevailing in the anthropogenic plumes reaching biogenic sources. In this situation, some comparisons with air quality measurements pointed out an improvement of simulated ozone concentrations when accounting for biogenic fluxes, both in urban plumes and over rural areas. (C) 2004 Elsevier Ltd. All rights reserved.