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As criteria pollutants from anthropogenic emissions have declined in the US in the last two decades, biomass burning (BB) emissions are becoming more important for urban air quality. Tracking the transported BB emissions and their impacts is challenging, especially in areas that are also burdened by anthropogenic sources like the Texas Gulf coast. During the Corpus Christi and San Antonio (CCSA) field campaign in Spring 2021, two long-range transport BB events (BB1 and BB2) were identified. The observed patterns of absorption Ångström Exponent (AAE), high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) BB tracer (f60), equivalent black carbon (eBC), acetonitrile and carbon monoxide (CO) during BB1 and BB2 indicated differences in the mixing of transported BB plumes with local anthropogenic sources. The combined information from HYSPLIT backward trajectory (BTs) and satellite observations revealed that BB1 had mixed influence of transported smoke plumes from fires in Central Mexico, the Yucatan peninsula, and the Central US, whereas BB2 was influenced majorly by fires in the Central US. The estimated transport time of smoke from the Mexican fires and the Central US fires to our study site were not too different (48–54 hours and 24–36 hours, respectively) and both events appeared to have undergone similar levels of atmospheric processing, as evident in the elemental ratios of bulk organic aerosol (OA). We observed a progression of f44 vs. f60 as a function of time elapsed during BB2. Positive matrix factorization (PMF) analysis of OA showed that BB1 had a mixture of organics from aged BB emission with an anthropogenic marine signal while the oxidized organic compounds from aged BB emissions dominated the aerosols during BB2. While aerosol measurements exhibited good agreement with respect to the BB designation, the CO and acetonitrile trends revealed more complicated source contributions. Our analysis from mobile and stationary measurements highlights that both CO and acetonitrile are likely impacted by local sources even during the BB events and specifically that acetonitrile cannot be used as a unique BB tracer for dilute BB plumes in an industrially influenced location. Finally, we provide evidence of the potential regional impacts of these transported BB events on urban O3 levels using measurements from the surface air quality monitoring network in Texas.

A novel technique has been developed to measure sulfur dioxide (SO2) using a modification of the existing electrochemical concentration cell (ECC) ozonesonde technology. The current sonde-based method to measure SO2 (i.e. the dual-sonde approach) involves launching two ozonesondes together with one of the sondes having a filter to remove SO2 at the inlet. The SO2 profile is determined by taking the difference between the measurements from the two instruments. The dual-sonde method works well in typical tropospheric conditions when [O3] > [SO2] but saturates when [SO2] > [O3] and has large uncertainties in the upper troposphere/lower stratosphere that would limit its effectiveness in measuring SO2 from an explosive volcanic eruption. Due to these limitations, several modifications were made to create a single-sonde system that would directly measure SO2 (i.e. the SO2 sonde). These modifications included (1) a positively biased ECC background current, (2) the addition of an O3 removal filter, and (3) the addition of a sample dryer. The SO2 sonde measures SO2 as a reduction in the cell current. There was a strong correlation (r2 > 0.94) between the SO2 sonde and a Thermo 43c analyzer during controlled laboratory tests and pre-flight tests. Varying humidity levels affected the SO2 sonde’s sensitivity (84.6 ± 31.7 ppbv/µA, 1σ = 37 %) during initial field tests, which was resolved by adding a sample dryer upstream of the O3 removal filter and pump inlet. This modification significantly reduced the variability and increased the sensitivity of the SO2 measurements (47 ± 5.8 ppbv/µA, 1σ = 12 %). Field tests included measurements near Kīlauea Volcano (before and during the 2018 eruption of the Lower East Rift Zone), Costa Rica’s Turrialba Volcano, and anthropogenic plumes from the Athabasca Oil Sands region of Alberta, Canada. This single SO2 sonde system is an effective, inexpensive instrument for measuring both ground-based and vertical profiles of SO2 from anthropogenic and natural sources (i.e. volcanic eruptions) over a wide range of concentrations.

The population of Texas has increased rapidly in the past decade. The San Antonio Field Study (SAFS) was designed to investigate ozone (O₃) production and precursors in this rapidly changing, sprawling metropolitan area. There are still many questions regarding the sources and chemistry of volatile organic compounds (VOCs) in urban areas like San Antonio which are affected by a complex mixture of industry, traffic, biogenic sources and transported pollutants. The goal of the SAFS campaign in May 2017 was to measure inorganic trace gases, VOCs, methane (CH₄), and ethane (C₂H₆). The SAFS field design included two sites to better assess air quality across the metro area: an urban site (Traveler's World; TW) and a downwind/suburban site (University of Texas at San Antonio; UTSA). The results indicated that acetone (2.52 ± 1.17 and 2.39 ± 1.27 ppbv), acetaldehyde (1.45 ± 1.02 and 0.93 ± 0.45 ppbv) and isoprene (0.64 ± 0.49 and 1.21 ± 0.85 ppbv; TW and UTSA, respectively) were the VOCs with the highest concentrations. Additionally, positive matrix factorization showed three dominant factors of VOC emissions: biogenic, aged urban mixed source, and acetone. Methyl vinyl ketone and methacrolein (MVK + MACR) exhibited contributions from both secondary photooxidation of isoprene and direct emissions from traffic. The C₂H₆:CH₄ demonstrated potential influence of oil and gas activities in San Antonio. Moreover, the high O₃ days during the campaign were in the NOₓ-limited O₃ formation regime and were preceded by evening peaks in select VOCs, NOₓ and CO. Overall, quantification of the concentration and trends of VOCs and trace gases in a major city in Texas offers vital information for general air quality management and supports strategies for reducing O₃ pollution. The SAFS campaign VOC results will also add to the growing body of literature on urban sources and concentrations of VOCs in major urban areas.

Exchanges of energy and mass between the surrounding air and plant surfaces occur below, within, and above a forest's vegetative canopy. The canopy also can lead to vertical gradients in light, trace gases, oxidant availability, turbulent mixing, and properties and concentrations of organic aerosols (OA). In this study, a high-resolution time-of-flight aerosol mass spectrometer is used to measure non-refractory submicron aerosol composition and concentration above (30 m) and below (6 m) a forest canopy in a mixed deciduous forest at the Program for Research on Oxidants: Photochemistry, Emissions, and Transport tower in northern Michigan during the summer of 2016. Three OA factors are resolved using positive matrix factorization: more-oxidized oxygenated organic aerosol (MO-OOA), isoprene-epoxydiol-derived organic aerosol (IEPOX-OA), and 91Fac (a factor characterized with a distinct fragment ion at m/z 91) from both the above- and below-canopy inlets. MO-OOA was most strongly associated with long-range transport from more polluted regions to the south, while IEPOX-OA and 91Fac were associated with shorter-range transport and local oxidation chemistry. Overall vertical similarity in aerosol composition, degrees of oxidation, and diurnal profiles between the two inlets was observed throughout the campaign, which implies that rapid in-canopy transport of aerosols is efficient enough to cause relatively consistent vertical distributions of aerosols at this scale. However, four distinct vertical gradient episodes are identified for OA, with vertical concentration differences (above-canopy minus below-canopy concentrations) in total OA of up to 0.8 μg/m3. The magnitude of these differences correlated with concurrent vertical differences in either sulfate aerosol or ozone. These differences are likely driven by a combination of long-range transport mechanisms, canopy-scale mixing and local chemistry. These results emphasize the importance of including vertical and horizontal transport mechanisms when interpreting trace gas and aerosol data in forested environments.

Accurate and consistent monitoring of anthropogenic combustion is imperative because of its significant health and environmental impacts, especially at city-to-regional scale. Here, we assess the performance of the Copernicus Atmosphere Monitoring Service (CAMS) global prediction system using measurements from aircraft, ground sites, and ships during the Korea United States Air Quality (KORUS-AQ) field study in May to June 2016. Our evaluation focuses on CAMS CO and CO2 analyses plus two higher resolution forecasts (16-km and 9-km horizontal resolution), to assess their capability in predicting combustion signatures over East Asia. Our results show a slight overestimation of CAMS CO2 with a mean bias against airborne CO2 measurements of 2.2, 0.7, and 0.3 ppmv for 16-km and 9-km CO2 forecasts, and analyses, respectively. The positive CO2 mean bias in the16-km forecast appears to be consistent across the vertical profile of the measurements. In contrast, we find a moderate underestimation of CAMS CO with an overall bias against airborne CO measurements of -19.2 (16-km), -16.7 (9-km), and -20.7 ppbv (analysis). This negative CO mean bias is mostly seen below 750 hPa for all three forecast/analysis configurations. Despite these biases, CAMS show a remarkable agreement with observed enhancement ratios of CO with CO2 over Seoul metropolitan and over the West Sea, where East Asian outflows were sampled during the study period. More efficient combustion is observed over Seoul (delta(CO)/delta(CO2) = 9 ppbv/ppmv) compared to the West Sea (delta(CO)/delta(CO2) = 28 ppbv/ppmv). This ‘combustion signature contrast’ is consistent with previous studies in these two regions. CAMS captured this difference in enhancement ratios (Seoul: 8-12 ppbv/ppmv, West Sea: ~30 ppbv/ppmv) regardless of forecast/analysis configurations. The correlation of CAMS CO bias with CO2 bias is relatively high over these two regions (Seoul: 0.64-0.90, West Sea: ~0.80) suggesting that the contrast captured by CAMS may be dominated by anthropogenic emission ratios used in CAMS. However, CAMS shows poorer performance in terms of capturing local-to-urban CO and CO2 variability. Along with measurements at ground sites over the Korean peninsula, CAMS produces too high CO and CO2 concentrations at the surface with steeper vertical gradients (~0.4 ppmv/hPa for CO2 and 3.5 ppbv/hPa for CO) in the morning samples than observed (~0.25 ppmv/hPa for CO2 and 1.7 ppbv/hPa for CO), suggesting weaker boundary layer mixing in the model. Lastly, we find that the combination of CO analyses (i.e., improved initial condition) and use of finer resolution (9-km vs 16-km) generally produce better forecasts.

Gas-phase biogenic volatile organic compounds (BVOCs) are oxidized in the troposphere to produce secondary pollutants such as ozone (O3), organic nitrates (RONO2), and secondary organic aerosol (SOA). The nitrate radical (NO3) is especially reactive towards isoprene and monoterpenes such as α-pinene. A zero-dimensional model has been used to investigate differences in oxidation and SOA production from these two BVOCs, especially with respect to hydroxyl radical (OH) and NO3, above and below a forest canopy in rural Michigan using local data and data from a monitoring site in Detroit. In all modeled scenarios, NO3 concentrations are relatively small (0.5–3 pptv); however, daytime concentrations below the canopy are two-to-three times larger than those above. In the rural scenario, NO3 contributes up to 20 % of daytime oxidation of α-pinene below the canopy, and this contribution increases to around 40 % in the polluted cases. Oxidation of isoprene is almost entirely dominated by reaction with OH, as expected. The most significant first-generation RONO2 formation mechanism varies significantly between scenarios and by canopy location. Nonetheless, in every scenario, daytime production of first-generation RONO2 through NO3 + α-pinene is more significant below the canopy than above. While SOA mass loadings are moderate (2 μg m−3 or less), total SOA production is consistently enhanced below the canopy, due to the combined effects of elevated isoprene and reduced NO concentrations. Furthermore, below the canopy, the total amount of RONO2 SOA produced through NO3 oxidation of α-pinene during the daytime (10:00–18:00), while small in absolute terms, is more than twice as large as the amount produced above the canopy during that time period in every scenario. In the rural ambient case, a minimum of 74 % of α-pinene RONO2 SOA is formed solely from initial oxidation by NO3. The relative abundances of HO2 and NO are shown to substantially impact both total SOA production and RONO2 SOA composition. The results presented emphasize the need for more detailed studies regarding the influence of NO3 throughout forest canopies in different environments.

A study on the lived experiences of 14 adult African American men, who grew up in low socioeconomic status (SES)households, was undertaken to determine factors that helped them overcome disadvantage and ultimately achievepositive life outcomes. Theoretically, the odds would seem to be stacked against them. Low SES is an especiallydifficult condition for many African Americans to overcome and may be a catalyst for under achievement ineducation, while fomenting antisocial behavior, and oppositional thinking. The reasons are manifold and complex;the literature graphically details social and economic inequities that occur in low SES environments. Throughpersonal demographic data and verbal reflections, the participants provided insights of events that led to positive lifeoutcomes. Keys to success were found in education attainment, athletic and extracurricular activities, and having atleast one adult mentor/role model whose nurturing, guidance, and love kept them on a straight line trajectory towardadulthood. Their life stories were dotted with influences owing to adult norms whose example helped them overcomelow SES quality of life issues including racially based contextual stressors.