We have rigorously characterized different sources of error in satellite-based HCHO / NO₂ tropospheric columns, a widely used metric for diagnosing near-surface ozone sensitivity. Specifically, the errors were categorized/quantified into (i) an inherent chemistry error, (ii) the decoupled relationship between columns and the near-surface concentration, (iii) the spatial representativeness error of ground satellite pixels, and (iv) the satellite retrieval errors.

Satellite-derived NO_x emissions from biomass burning are estimated with TROPOMI observations. Two common emission estimation methods are applied, and sensitivity tests with model output were performed to determine the accuracy of these methods. The effect of smoke aerosols on TROPOMI NO₂ columns is estimated and compared to aircraft observations from four different aircraft campaigns measuring biomass burning plumes in 2018 and 2019 in North America.

Iodide-adduct chemical ionization mass spectrometry (I-CIMS) has been widely used to analyze airborne organics. In this study, I-CIMS sensitivities of isomers within a formula are found to generally vary by 1 and up to 2 orders of magnitude. Comparisons between measured and predicted moles, obtained using a voltage-scanning calibration approach, show that predictions for individual compounds or formulas might carry high uncertainty, yet the summed moles of analytes agree reasonably well.

We present a comparison of the changes to light absorption behavior and chemical composition of wildfire smoke particles from day- and nighttime oxidation processes and discuss the results within the context of previous laboratory findings.

We measured radical yields of aqueous PM_2.5 extracts and found lower yields at higher concentrations of PM_2.5. Abundances of water-soluble transition metals and aromatics in PM_2.5 were positively correlated with the relative fraction of •OH but negatively correlated with the relative fraction of C-centered radicals among detected radicals. Composition-dependent reactive species yields may explain differences in the reactivity and health effects of PM_2.5 in clean versus polluted air.

Measurement techniques that can achieve molecular characterizations are necessary to understand the differences of fate and transport within isomers produced in the atmospheric oxidation process. In this work, we develop an instrument to conduct isomer-resolved measurements of particle-phase organics. We assess the number of isomers per chemical formula in atmospherically relevant samples and examine the feasibility of extending the use of an existing instrument to a broader range of analytes.

Emissions of volatile organic compounds (VOCs) from plants are important for tropospheric ozone and secondary organic aerosol (SOA) formation. Real plant emissions are much more diverse than the few proxies widely used for studies of plant SOA. Here we present the first study of SOA from Californian sage plants and the oxygenated monoterpenes representing their major emissions. We identify SOA products and show the importance of the formation of highly oxygenated organic molecules and oligomers.