Atmospheric chemistry and aerosol associated with the coastal urban environment

This study aims to understand the dynamics of atmospheric secondary organic aerosol (SOA) in Houston, Texas. It (1) explores the relationship between sea breeze and air quality, (2) investigates the spatiotemporal characteristics of aerosols and SOA formation rates, and (3) analyzes factors that impact new particle formation (NPF). Long-term monitoring demonstrated that PM2.5 (particles with diameters of 2.5 m or smaller) concentrations are ~30% larger on days with southerly wind or sea breeze recirculation compared to those under other wind patterns. On southerly wind days, 53% of PM2.5 was attributed to long-range transport of soil. In contrast, on sea breeze recirculation days, 60% of PM2.5 was attributed to anthropogenic sources and only 15% to soil sources. SOA also appeared to be important on sea breeze recirculation days. To investigate in-situ SOA mechanisms and NPF in Houston, aerosol composition and size distribution were measured during the TRACER field campaign from July to September 2022. During this campaign, OA contributed the most significant fraction of aerosol. Assuming two OA factors - less-oxidized oxygenated OA (LO-OOA), and more-oxidized oxygenated OA (MO-OOA) - represent SOA, a mass balance model was used to estimate the SOA formation rate. For MO-OOA, the largest formation rates aligned with intense photo-oxidation processes. For LO-OOA, the most significant formation rates occurred at night, likely associated with nitrate radical chemistry. Substantial differences in particle compositions and concentrations were observed on NPF and non-NPF days. PM1 mass concentrations were 7% to 76% lower on NPF days compared to non-NPF days across all sites. However, the fractional increase in the contributions of sulfate and MO-OOA on NPF days allows enhanced uptake of gases. These results suggest that, given similar condensation sinks, other atmospheric conditions play a critical role in determining the occurrence of NPF. This study provides a comprehensive investigation of SOA formation, NPF, and impacts of meteorological conditions in Houston. These findings contribute to efforts to improve air quality in coastal urban areas in order to meet the National Ambient Air Quality Standards.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Engineering

Grantor

Rice University

Year dc:date.issued

2025

Author dc:creator

• Chao, Chun-Ying

Advisors dc:contributor.advisor

• Cohan, Daniel S
• Griffin, Robert J

• atmospheric chemistry
• air pollution

Statement dc:rights

• Copyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1911/118389

OAI identifier oai:identifier

oai:repository.rice.edu:1911/118389