What is the effect of urban emission of acid gases (NO₂ and SO₂) on the physical and chemical properties of aerosols? -

Abstract

Beirut, which lies at the Eastern Mediterranean shore, is subject to two different types of dust storms. These dust storms, which are of Arabian or African origins and have different characteristics, result in an increase in total particulate matter concentration in the atmosphere. Atmospheric aerosols are subject to mixing with acid gases, anthropogenic pollution, and marine particles resulting in physical and chemical transformations of primary particles along with the formation of secondary ones. Dust storms result in a total increase in the acidic gases HONO, HNO₃ and H₂SO₄. Along with the direct deposition effects on the environment, acidic gases influence the inorganic content of particulate matter; mainly nitrates and sulfates. The change in chemical content and properties of aerosols is coupled to change in particles’ morphology. Furthermore, due to their different trajectories, dust storms result in different bacterial and fungal counts in particulate matter. In this thesis, a comprehensive evaluation of the changes in bacterial and fungal content, morphology, sizes and chemical transformations of dust particles and their effect on the re-evaporation of acid gases and the deposition of aged and more soluble particles is offered. Results can be incorporated in regional models of aerosol transport, used for raising awareness related to health issues during dusty days and inform regulatory agencies on the changes and their impacts on the ecosystem during dusty episodes.