Nucleation and growth of sulfate aerosol in coal-fired power plant plumes: sensitivity to background aerosol and meteorology

摘要

New-particle formation in the plumes of coal-fired power plants and otheranthropogenic sulfur sources may be an important source of particles in theatmosphere. It remains unclear, however, how best to reproduce thisformation in global and regional aerosol models with grid-box lengths thatare 10s of kilometers and larger. The predictive power of these models isthus limited by the resultant uncertainties in aerosol size distributions.In this paper, we focus on sub-grid sulfate aerosol processes withincoal-fired power plant plumes: the sub-grid oxidation of SO withcondensation of HSO onto newly-formed and pre-existingparticles. We have developed a modeling framework with aerosol microphysicsin the System for Atmospheric Modelling (SAM), a Large-EddySimulation/Cloud-Resolving Model (LES/CRM). The model is evaluated againstaircraft observations of new-particle formation in two different power-plantplumes and reproduces the major features of the observations. We show howthe downwind plume aerosols can be greatly modified by both meteorologicaland background aerosol conditions. In general, new-particle formation andgrowth is greatly reduced during polluted conditions due to the largepre-existing aerosol surface area for HSO condensation andparticle coagulation. The new-particle formation and growth rates are also astrong function of the amount of sunlight and NO since both control OHconcentrations. The results of this study highlight the importance forimproved sub-grid particle formation schemes in regional and global aerosolmodels.