Caracterización de la distribución de tamaños y propiedades higroscópicas del aerosol atmosférico en España mediante analizadores de movilidad diferencial

Zusammenfassung

The knowledge and characterization of the physical properties of atmospheric aerosols is of great importance to assess their behavior in the atmosphere and their impact on human health, climate and ecosystems. This doctoral thesis focuses on the experimental study of two physical properties of the submicrometer fraction of the atmospheric aerosol in Spain, in particular on its size distribution and hygroscopicity. The measurements have been obtained in different locations of Spain by instruments that classify the aerosol particle size by using the Differential Mobility Analyzer (DMA) technique. The observations of aerosol number size distribution were measured by commercial instruments, Scanning Mobility Particle Sizer (SMPS) and an Ultrafine Particle Monitor (UFPM). However, in order to measure the aerosol hygroscopic growth distribution, it was necessary to build a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA). Spatial and temporal variability of the particle number size distributions were analyzed in Spain, finding significant variations related to the local and regional sources of each site of measurement, as well as meteorological factors. These last ones determined the differences found between coastal and inland regions of the peninsula. In the case of Madrid, the dynamic processes of urban background aerosol due to a gradual decrease in the particle size were frequent during the warm period and lead to variations in particle size distributions. The changes experienced by the size distributions of the aerosol particles in the suburban atmosphere of the city were also manifested in the aerosol hygroscopic behavior. The hygroscopic variability of the particles was conditioned by the emission sources in the city that determine the aerosol composition and the transformation that they suffer in the atmosphere associated with the meteorology and its interaction with gaseous pollutants. Aerosol hygroscopicity depended on particle size, and the greater the particle size measured, the higher coating by hydrophilic species, and therefore, its hygroscopicity is higher. The results obtained in this thesis not only represent a great progress in the current level of knowledge on some physical properties of the atmospheric aerosol, but also will contribute significantly to improve the state-of-art on their behavior in the atmosphere, particularly in midlatitudes and areas of Southern Europe.