Griffin, Robert J.2021-12-062021-12-062021-122021-12-02December 2Guo, Fangzhou. "Sources and Characterization of Ozone and Submicron Aerosol in San Antonio, Texas." (2021) Diss., Rice University. <a href="https://hdl.handle.net/1911/111751">https://hdl.handle.net/1911/111751</a>.https://hdl.handle.net/1911/111751The work presented here describes the observations of 1) the criteria air pollutant ozone (O3) and its precursors- nitrogen oxides (NOX) and volatile organic compounds (VOCs) and 2) non-refractory submicron aerosol (NR-PM1) at two sites in the city of San Antonio, Texas. Chemical modeling and source apportionment techniques are used to characterize the reaction pathways and sources of the observed pollutants. A customized urban-scale zero-dimensional model is created to calculate the rate of change in concentration of proxies for secondary aerosols across the urban core. Based on the inter-site comparison of ozone modeling results, we discover that San Antonio is mostly in a NOX-sensitive O3 formation regime throughout the daytime during the campaign. In general, O3 destruction rate is one order of magnitude smaller than the O3 formation rate, leading to a large net O3 production. The VOCs exhibiting high reactivity are formaldehyde, isoprene, and alkenes. The existence of an elevated regional O3 level combined with strong solar radiation and local O3 formation could lead to non-attainment or near non-attainment on high O3 days. These results suggest emissions control strategies for NOX to reduce direct local O3 production. Emissions control on VOCs, including formaldehyde precursors, could also help in reducing the regional background O3. These altogether would decrease the O3 level during the late spring peak in San Antonio. A customized urban-scale zero-dimensional model is created to calculate the rate of change in concentration of proxies for secondary aerosols across the urban core of San Antonio. Detailed parameterization and sensitivity tests provide the basis for us to discover that oxygenated organic aerosol (OOA) species experience a reactive chemical loss during the transport. Strong parabolic relationships between the net chemical reaction rate of less oxidized (LO)-OOA and ambient temperature is observed, which is the first field observation of the temperature impact on secondary organic aerosol formation rate, consistent with the relationship in concentrations predicted for earlier chamber simulation studies. More oxidized (MO)-OOA does not show such a relationship likely due to it being more oxidized, less volatile, and less reactive. More active chemical formation occurs if the air gets warm enough and oxidants are at a significant enough level during the transport across the urban core. The modeling results also indicate a very small net loss rate of sulfate aerosol during the transport across the city and negligible sulfate formation from local sources. The backward trajectories cluster analysis categorizes the air inflow during the campaign period into “Oceanic”, “Near Inland”, and “Continental” scenarios. Higher NR-PM1 loadings in Oceanic scenarios are driven mostly by high sulfate and ammonium. The averaged mass loadings of sulfate and ammonium nearly triple from Continental to Oceanic scenarios. Organics are relatively consistent, and nitrate and chloride altogether contribute less than 2.5% of the total NR-PM1 on a mass basis. Aerosol liquid water (ALW) contents and inorganic aerosol pH calculated using a thermodynamic model decrease from Oceanic to Continental scenarios. A positive trend between estimated methanesulfonic acid (MSA) and binned ALW under relatively acidic conditions is observed. MSA also correlates well with sulfate, suggesting shared oxidation pathways of secondary species along the transport pathway. Regional source contribution function analysis reveals major sources of anthropogenic sulfates on the western and central Gulf and a few hot spots on southern and eastern Texas. Biogenic sulfates mostly originate in the coastal and central Gulf.application/pdfengCopyright 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.Atmospheric PollutantsSubmicron AerosolOzoneChemistry ModelingSource ApportionmentThesis2021-12-06