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.Simplified schematic of the scanning mobility particle sizer (SMPS) system used to measure the fraction of positively ... Transport efficiencies of Nano-SMPS system and Regular-SMPS system. ... Schematic diagram of the dual SMPS system.
|Title||:||Atmospheric Nucleation: Development and Application of Nanoparticle Measurements to Assess the Roles of Ion-induced and Neutral Processes|
|Publisher||:||ProQuest - 2008|