Modifying Environmental Chambers for Varying Applications: From Evaluating Secondary Organic Aerosol Formation to Health Effects Investigation with Animal Exposure
- Author(s): Li, Qi
- Advisor(s): Cocker, David R
- et al.
Camphene is one of the dominant monoterpenes measured in biogenic and biomass burning emission samples but is not well-studied in environmental chambers. This thesis conducted a series of experiments in the UCR environmental chamber to explore the SOA formation from OH-initiated oxidation of camphene and properties for the first time across a range of conditions. Experiment results were compared with modeling simulations done by two chemically detailed box models, Statewide Air Pollution Research Center (SAPRC) and Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A). Experiments performed with added nitrogen oxides (NOx) resulted in higher SOA yields (up to 64 %) than experiments performed without added NOx (up to 28 %). Further analysis based on modeling results revealed a possible undervaluation of RO2 chemistry role in previous SOA studies. SAPRC modeling of the chamber studies suggested that the higher SOA yields at higher initial NOx levels were primarily due to higher production of peroxy radicals (RO2) and the generation of highly oxygenated organic molecules (HOMs) formed through unimolecular RO2 reactions. Volatile Consumer Products (VCPs) is another VOC emission source that plays a growing important role in the total VOC emissions. Oxidation experiments on some low vapor pressure VOCs (LVP-VOCs) have shown high potentials of SOA formation while the low vapor pressure feature is challenging the traditional environmental chamber facilities for getting consistent results due to the varying chamber design and experimental protocols. This thesis, for the first time, compared two widely known environmental chamber systems- UCR chamber and Caltech chamber. A series of experiments on the oxidation of benzyl alcohol was conducted as a case study to assist the comparison. The valuable findings derived from the analysis of chamber differences include refined chamber experimental protocols, static charge effects being reflected in particle–wall interactions, etc. Findings from comparison were considered and reflected in the renewed 2021 UCR fixed volume chamber, in which encouraging results were observed, including orders of magnitude lowered contamination background level, and over 70% decrease in averaged particle number decay rate due to wall loss. The environmental chamber system was modified to fit animal exposure study. Particulate matters (PMs) are related to multiple respiratory diseases. However, the mechanism of health effects of particulate matters is still unclear. To meet the requirement of varying objectives, multiple sets of animal whole-body exposure chamber systems were built for different types of PMs and experimental conditions. A series of PMs-exposure experiments were conducted to investigate the health effects of Salton Sea Spray on mice, in which the gene expression analysis data suggested PMs from different sources may have a possible synergistic effect on mice lungs.