UC Berkeley

Nitrogen oxides (NO_y) in Earth's troposphere exert control over the production of ozone (O₃) and particulate matter. In this dissertation the role of NO_y in the formation of secondary organic aerosols (SOA) is investigated using theoretical as well as both existing and new analytical techniques. A number of insights are gained into the process through which SOA is formed, and the chemical composition of SOA formed through oxidation of volatile organic compounds (VOCs) in the presence of NO_x.

In Chapter 2, I review the theoretical basis for understanding the formation of SOA in the atmosphere and the role of NO_y in the context of this theory. Expectations for how the chemistry of NO_x influences SOA formation and composition in the atmosphere are discussed in the context of previously reported laboratory measurements. In Chapter 3, I describe a chamber study quantifying the formation of organic nitrates and SOA through the oxidation of isoprene by the nitrate radical (NO₃) and discuss the importance of this SOA source on a global scale. The importance of multiple stages of isoprene oxidation by NO₃ is investigated and quantified for the first time. In Chapter 4, I investigate the degree to which organic nitrates in aerosols can be quantified using an Aerodyne Aerosol Mass Spectrometer (AMS). How aerosol organic nitrates affect the current understanding of organic aerosol composition obtained via AMS is discussed. In Chapter 5, I describe a new instrument capable of quantifying organic nitrates in particles, representing a significant advance in the analysis of the chemical composition of organic aerosols. This instrument is used in the laboratory to quantify the formation of organic nitrates in particles formed through high-NO_x photooxidation of a number of SOA precursors.