Type of Document Dissertation Author Zaveri, Rahul A. Author's Email Address email@example.com URN etd-7197-18361 Title Development and Evaluation of a Comprehensive Tropospheric Chemistry Model for Regional and Global Applications Degree PhD Department Chemical Engineering Advisory Committee
Advisor Name Title Conger, William L. Little, John C. Neu, Wayne L. Saylor, Rick D. Peters, Leonard K. Committee Chair Keywords
- Air quality model
- aerosol chemistry
- aqueous chemistry
Date of Defense 1997-06-27 Availability unrestricted AbstractAccurate simulations of the global radiative impact of anthropogenic
emissions must employ a tropospheric chemistry model that predicts
realistic distributions of aerosols of all types. The need for a such
a comprehensive yet computationally efficient tropospheric chemistry
model is addressed in this research via systematic development of the
various sub-models/mechanisms representing the gas-, aerosol-, and
The gas-phase model encompasses three tropospheric chemical regimes -
background and urban, continental rural, and remote marine.
The background and urban gas-phase mechanism is based on the paradigm
of the Carbon Bond approach, modified for global-scale applications.
The rural gas-phase chemistry includes highly condensed isoprene and
a-pinene reactions. The isoprene photooxidation scheme is adapted for
the present model from an available mechanism in the literature, while
an a-pinene photooxidation mechanism, capable of predicting secondary
organic aerosol formation, is developed for the first time from the
available kinetic and product formation data. The remote marine gas-
phase chemistry includes a highly condensed dimethylsulfide (DMS)
photooxidation mechanism, based on a comprehensive scheme available
in the literature. The proposed DMS mechanism can successfully explain
the observed latitudinal variation in the ratios of methanesulfonic
acid to non-sea-salt sulfate concentrations.
A highly efficient dynamic aerosol growth model is developed for
condensing inorganic gases. Algorithms are presented for calculating
equilibrium surface concentrations over dry and wet multicomponent
aerosols containing sulfate, nitrate, chloride, ammonium, and sodium.
This alternative model is capable of predictions as accurate for
completely dissolved aerosols, and more accurate for completely dry
aerosols than some of the similar models available in the literature.
For cloud processes, gas to liquid mass-transfer limitations to
aqueous-phase reactions within cloud droplets are examined for all
absorbing species by using the two-film model coupled with a
comprehensive gas and aqueous-phase reaction mechanisms. Results
indicate appreciable limitations only for the OH, HO2, and NO3
radicals. Subsequently, an accurate highly condensed aqueous-phase
mechanism is derived for global-scale applications.
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