Aerosol Dynamics in an Urban Atmosphere

Citation

Peterson, Thomas William (1978) Aerosol Dynamics in an Urban Atmosphere. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/e8gt-t984. https://resolver.caltech.edu/CaltechTHESIS:07182024-181126325

Abstract

This work examines three aspects of modeling the dynamic behavior of an atmospheric aerosol distribution. First, a steady state, three-dimensional solution of the atmospheric diffusion equation including settling, deposition, and first order removal is presented. The solution is applied to the prediction of airborne concentrations of gaseous and particulate pollutants in the case in which gases are converted to secondary particulate matter . The conversion of sulfur dioxide, nitrogen oxides, and hydrocarbons to particulate sulfate, nitrate, and organics in the Los Angeles atmosphere and urban plume is analyzed.

Second, the dynamic behavior of aerosol size distributions under the influence of coagulation and growth by heterogeneous condensation of gaseous species is studied. Analytical solutions are obtained to the integro-differential equation governing the aerosol size distribution density function. Two modes of coagulation (constant and linear coagulation kernels) and two modes of condensation (growth independent of particle volume and linearly dependent on particle volume) are considered. Also included are simplified mechanisms for nucleation and removal of aerosol particles. The interaction of these mechanisms on aerosol size distributions is elucidated.

Finally, a detailed study of heterogeneous condensation on and reaction within an aerosol particle is undertaken. All important mechanisms governing the transfer of pollutants from the gas to the particulate phase are discussed, and the general framework for describing heterogeneous reaction within the particle is constructed. The model is then used to describe growth and composition change of a marine aerosol exposed to SO₂, NH₃ and H₂SO₄.

Thesis Files