UC Riverside

ABSTRACT OF THE DISSERTATION

Aerosol Optical Properties in Field Measurements and Smog Chamber Experiments With Selected Biogenic and Anthropogenic Precursors

by

Justin Hernandez Dingle

Doctor of Philosophy, Environmental Toxicology Graduate Program

University of California, Riverside, June 2018

Dr. Roya Bahreini, Chairperson

The chemical, optical, and microphysical properties of aerosols in the atmosphere impacts climate, visibility, ecosystems, and human health. There are many techniques to study aerosols, but there are still characteristics of aerosols that areas of study are needed. The climate effects of aerosol have significant uncertainties due to the limited information on the optical properties of secondary organic aerosols (SOA) and their role in climate models in relationship to their chemical and microphysical properties. The presented work in this dissertation highlights measurement and sampling techniques made by various instrumentation to study the chemical, optical, and microphysical properties of aerosols in field and laboratory studies.

The study of aerosols was carried out in an airborne field campaign in the Colorado Front Range (Summer, 2014) and indoor laboratory smog chamber in the oxidation of anthropogenic and biogenic hydrocarbon precursors to better characterize the important properties and parameters of aerosols. The content of this dissertation will address:

1) The impacts of aerosol optical extinction on the air quality in the Colorado Front Range during the Front Range Air Pollution and Photochemistry Experiment (FRAPPÉ) 2014.

Measurements of aerosol extinction coefficient at 632 nm were made aboard the NSF C-130 aircraft to study aerosol optical properties under fresh and aged air masses and the impacts of various emission source to aerosol extinction.

2) The oxidation of 1-methylnaphthalene, phenol, toluene, longifolene, and α-pinene hydrocarbon precursors in smog chamber studies.

We present optical properties of SOA derived from the oxidation of different hydrocarbon precursors to study the complex refractive index of SOA. With the emergence of new information on brown carbon (BrC) aerosols, it is imperative to study their chemical, optical, and microphysical properties and their impacts on climate change since the BrC aerosol have absorbing characteristics thus contributing to warming effects on climate. Here we aim to understand the behavior of aerosols under different chamber conditions and evaluate the real (n) and imaginary (k) part of the refractive index of anthropogenic and biogenic aerosols as well as the single scattering albedos (SSA) and mass absorption coefficient (MAC).