Lee Tiszenkel

Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Atmospheric Science

Committee Chair

Shanhu Lee

Committee Member

Larry Carey

Committee Member

Kevin Knupp

Committee Member

Arastoo Pour Biazar

Committee Member

Phil Bitzer


Atmospheric chemistry, Atmospheric aerosols--Environmental aspects, New particle formation (NPF)


New particle formation (NPF) is a process that impacts climate, air quality and human health. NPF occurs in a diverse range of environments, initiated by a variety of different chemical precursors in the atmosphere, including anthropogenic pollutants and organic compounds emitted by vegetation. In highly populated urban areas, newly formed particles can be scavenged during their initial steps of formation by coagulation with pre-existing particles. Thus, NPF must occur rapidly to explain observed NPF events in polluted urban environments. The presence of reduced nitrogen compounds such as ammonia and amines is key to these formation processes. These compounds have a strong association with anthropogenic activity such as traffic, agriculture, and industry, but accurate on-line measurements of these ubiquitous atmospheric compounds are rare. Several essential questions remain about the rapid mechanisms responsible for urban NPF; as these mechanisms occur in areas of the highest population density, a comprehensive understanding of NPF in these environments is essential to form mitigation strategies for air quality in a rapidly urbanizing world. In more remote regions, oxidized organic compounds that result from the reaction of ozone with VOCs emitted by vegetation such as monoterpenes play a significant role in NPF processes. Much of the chemistry and mechanisms behind this process remain obscure, as well; namely, the presence of isoprene has been associated with a suppression of NPF but there are contrasting theories as to the chemistry associated with these processes. Here, we present work aimed to answer these open questions about NPF. We made comprehensive measurements of particle size distributions, aerosol chemical composition, and NPF precursors, including sulfuric acid, base compounds, and oxidized organics, in highly polluted Houston, TX. We designed laboratory experiments to determine the precise mechanisms of isoprene suppression of NPF. We also investigated ammonia and amines in Houston on a more granular level, as well as the association of indoor ammonia and amine concentrations with human activity. This research found evidence for a multicomponent NPF process in urban areas that involves sulfuric acid, amines and highly oxidized organic molecules that is consistent with experimental results from CERN’s CLOUD chamber. In the laboratory, we observed a synergetic mechanism for isoprene suppression of biogenic NPF that involves the presence of HOx. Finally, we present comprehensive measurements of reduced base compounds in the urban atmosphere.

Available for download on Wednesday, December 11, 2024