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University of Arizona (2021)

Aerosol and Precipitation Physicochemical Properties in Arid Regions

Cuevas Robles, Alberto

Titre : Aerosol and Precipitation Physicochemical Properties in Arid Regions

Auteur : Cuevas Robles, Alberto

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 2021

Résumé partiel
Airborne aerosols represent an important component of the Earth’s atmosphere. They consist of a heterogeneous mixture of solid and liquid particles of varying composition and phase, originated from a wide variety of natural and anthropogenic sources. Primary aerosols are directly emitted to the atmosphere derived from mineral dust, sea salt, biological materials, volcanic eruptions, biomass burning, fuel combustion, road traffic suspension, among others. On the other hand, secondary aerosols are formed by gas-to-particle conversion in the atmosphere by means of nucleation and condensation of gaseous precursors, producing more highly oxidized, less volatile species, which can form new particles or condense on the surface of other particles. The impacts of aerosols on the atmosphere, climate and public health are currently among the most important topics in environmental studies. The exposure to particulate matter (PM) can cause respiratory diseases and result in mortality, and the ability to pose health risks depends upon the size, concentration and chemical composition of suspended particles. Heavy metals (HMs) such Fe, Al, Zn, Pb, Cr, Ni, Co, Cu and Cr, associated with PM are also of toxicological interest due to their influence on normal human biological functions. Urbanization, high industrialization, vehicle emissions and suspension from paved and unpaved roads can result in significant increase of PM concentrations in ambient air. A considerable fraction of ambient PM exposure leading to human health impacts occurs in cities, due to higher population density, human activities and their emissions to the air. However, high PM exposure can also result from biomass burning for household and commercial needs, and high incidence of natural dust events in rural areas. Aerosol particles also have the ability to impact the Earth’s climate system via several physical mechanisms, including (1) scattering and absorbing solar radiation, (2) scattering, absorbing and emitting thermal radiation, and (3) acting as cloud condensation nuclei (CCN) and ice nuclei (IN). An important factor to consider when evaluating the effects of PM, is the hygroscopic growth, which is strongly influenced by relative humidity (RH). It plays a key role not only in numerous atmospheric processes such as climate forcing, visibility degradation and cloud formation, but it also plays a very important role on the impact of PM on human health. The behavior and fate of inhaled PM in the human respiratory system is important for knowledge of inhalation toxicology. Inhaled particles that are hygroscopic and pass through a humid environment such as the human respiratory airways, usually absorb the water vapor present, impacting the particles physical characteristics, including size, shape and density, thus affecting their total and regional deposition in different parts of the human respiratory system.

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