The impact of new particle formation on regional air quality and CCN formation is for the first time explored using the UAM-AERO air quality model. New particles are formed by ternary nucleation of sulfuric acid, ammonia and water; subsequent growth of clusters to large sizes is driven by condensation of sulfuric acid and organic vapors, as described by the recently developed nano-Köhler theory. Application of the model in Athens (GAA) and Marseilles (GMA) reveals higher sulfuric acid condensational sink and gaseous sulfuric acid (hence nucleation rate) for the latter. However, limited quantities of organic vapors in the GMA inhibit the growth of the formed clusters; therefore new particle formation is more efficient in the GAA. A sensitivity analysis demonstrates that (1) uncertainty in vaporization enthalpy does not affect organic carbon formed by nucleation, and (2) an accommodation coefficient of unity gives excellent agreement of condensation sink with in-situ observations. Nucleation affects the aerosol size distribution, and can be an important contributor to CCN; locally it can be more important than chemical ageing of pre-existing aerosols.

The estimation of odor production and dispersion from landfill sites is a very complicated task because of the different chemical species that exist in biogas. To site a new landfill, it is necessary to know the distance that odors can travel around the landfill under atmospheric conditions that increase the concentration of pollutants. Although CH₄ is an odorless gas, it can be used as an index to determine the dispersion of low-reactivity odorous species around a landfill site. Methane production rates, estimated by biogas production models, were used by an air dispersion model to determine the spatial distribution of CH₄ around landfill sites. By utilizing dispersion models under extreme atmospheric conditions, a maximum CH₄ concentration around the landfills was determined. Based on the ratio between CH₄ and odorous chemical species, the spatial distribution of the concentration of an odorous species was determined for those species with low reactivity in the atmosphere. For odorous species with high reactivity in the atmosphere, a dispersion-reaction model must be used. In this way, the acceptable distance between new landfills and residential areas can be determined. The proposed methodology could be used as a design tool for those who are interested in landfill siting.