The major purpose of my Ph.D. study was to enhance our current understanding of new
particle formation (NPF) processes in the atmosphere. My contributions include: (1)
performing field measurements of atmospheric aerosols and subsequent data analysis of
nucleation events, and (2) improving the performance of instruments commonly used for
atmospheric aerosol measurements. My acquisition and analysis of atmospheric data
involved studying the fraction of electrically charged particles, f , in the 3-25 nm range to
obtain information on nucleation and subsequent growth process in the atmospheric
boundary layer. Chapter 2 shows that the initial charge states of nucleated particles can
be inferred from known diameter growth rates and measured values of charged fractions f
in the 3-6nm range. By this means I was able to show that ion-induced nucleation did not
contribute significantly to NPF events observed in Boulder, Colorado. Chapter 3 applies
and extends the concepts that were introduced in Chapter 2. In this chapter I show that
the diameter growth rates of particles during NPF events can be estimated from the
measured size dependent charged fractions of particles in the 4-25 nm range and applied
the technique to infer growth rates during NPF events observed in Mexico City. My
work on instrument development involved theoretical and experimental studies aimed at
reducing the size detection limit of a laminar flow condensation particle counter (CPC).
Theoretical studies showed that preferred CPC working fluids for activating the growth
of the smallest possible size are those having high surface tension and low vapor pressure.
Experiments were performed using selected working fluids in the prototype ultrafine
CPC developed by Stolzenburg and McMurry. Results show that diethylene glycol and
oleic acid can sometimes activate the growth of particles having geometric diameter as
small as 1 nm, and can always efficiently detect particles down to 1.5 nm.
University of Minnesota Ph.D. dissertation. January 2008. Major: Mechanical Engineering. Advisor: Peter H. McMurry. 1 computer file (PDF); xii, 173 pages, includes appendices.
Atmospheric nucleation : development and application of nanoparticle measurements to assess the roles of ion-induced and neutral processes.
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