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Acid-Catalyzed Heterogeneous Reactions and Secondary Organic Aerosol Formation From Biogenic Compounds
EPA Grant Number: U916146Title: Acid-Catalyzed Heterogeneous Reactions and Secondary Organic Aerosol Formation From Biogenic Compounds
Investigators: Czoschke, Nadine
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Thompson, Delores
Project Period: January 1, 2003 through January 1, 2006
Project Amount: $84,561
RFA: STAR Graduate Fellowships (2003)
Research Category: Academic Fellowships , Fellowship - Atmospheric Sciences , Air Quality and Air Toxics
Description:
Objective:The overall objective of this research project is to determine the impact of acid-catalyzed heterogeneous reactions on secondary organic aerosol (SOA) formation. The specific objectives of this research project are to: (1) evaluate the temperature and humidity dependence of these heterogeneous reactions; and (2) incorporate heterogeneous reactions into a photochemical kinetic model of atmospheric secondary aerosol formation.
Approach:There are two experimental phases to this project:
a laboratory phase and a chamber phase. The laboratory portion involves the
ozonation of
various biogenics in 500 L Teflon bags and a 4-meter-long flow reactor to determine
the short-term (seconds to 1 hour) qualitative effects of an acidic aerosol
environment on SOA growth. Results from these experiments have shown that an
acidic atmosphere leads to increases in SOA growth for a variety of biogenics
including isoprene, acrolein, and 
-pinene. Experiments in a newly built University
of North Carolina 270 m3 dual chamber Teflon smog chamber will be used for
the second experimental phase. Experiments in these chambers will quantitatively
assess the temperature and humidity effects of heterogeneous reactions on SOA
growth. The ozonation of -pinene in the absence of light and the photo-oxidation
of a-pinene in the presence of NOx will be studied in this phase. The use of
a larger reaction volume will allow longer time scales to be evaluated and
reduce the wall effects of the chamber compared to the 500 L Teflon bags. Filter
and denuder samples will be analyzed using gas chromatography/mass spectrometry,
and diverse derivitization techniques will be used to identify the gas- and
particle-phase concentrations of the oxidation products and possible heterogeneous
reaction products. The results of these chamber experiments also will be used
to incorporate acid-catalyzed heterogeneous reactions into an existing photochemical
kinetic solver for the -pinene system.
fellowship, secondary organic aerosol, SOA, acid-catalyzed heterogeneous reactions, acid catalyst, photochemical kinetic model, aerosol formation.