Tracers of secondary organic aerosols (SOA) from thirteen aromatic hydrocarbons were quantified in laboratory smog chamber experiments. Class-specific SOA tracers emerged, including 2,3-dihydroxy-4-oxo-pentatonic acid (DHOPA) from monoaromatic volatile organic compounds (VOCs), phthalic acid from naphthalene and 1-methylnaphthalene, and methyl-nitrocatechol isomers from o,m,p-cresol oxidation. Organic carbon mass fractions (fSOC) for these and other tracers were determined and extend the SOA tracer method widely used to apportion biogenic SOC. The extended SOA tracer model was applied to evaluate the sources of SOC in Atlanta, GA during summer 2015 and winter 2016 after modifying the chamber-derived fSOC¬ values to reflect SOA yields and local VOC levels (fSOC’). Monoaromatic, diaromatic, and cresol SOC contributed an average of 24%, 8%, and 0.12% of organic carbon (OC) mass during summer and 17%, 5%, and 0.27% during winter, respectively. Cresol SOC peaked during winter and was highly correlated with levoglucosan (r=0.93, p<0.001), consistent with it originating from biomass burning. Together, aromatic, biogenic, and biomass burning derived SOC accounted for an average of 77% and 28% of OC in summer and winter, respectively. The new understanding of SOA composition from aromatic VOCs advances the tracer-based method by including important precursors of SOC and enables a better understanding of the sources of atmospheric aerosol. This dataset is associated with the following publication: Al-Naiema, I.M., J. Offenberg, C.J. Madler, M. Lewandowski, J. Kettler, T. Fang, and E.A. Stone. Secondary Organic Aerosols from Aromatic Hydrocarbons and their Contribution to Fine Particulate Matter in Atlanta, Georgia. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, USA, 223: 117227, (2020).

The relationship between the oxidation state and relative volatility of secondary organic aerosol (SOA) from the oxidation of a wide range of hydrocarbons is investigated using a fast-stepping, scanning thermodenuder interfaced with a high resolution time-of-flight aerosol mass spectrometer (AMS). SOA oxidation state varied widely across the investigated range of parent hydrocarbons but was relatively stable for replicate experiments using a single hydrocarbon precursor. On average, unit mass resolution indicators of SOA oxidation (e.g., AMS f43 and f44) are consistent with previously reported values. Linear regression of H:C vs O:C obtained from parameterization of f43 and f44 and elemental analysis of high resolution spectra in Van Krevelen space both yield a slope of ~0.5 across different SOA types. A similar slope was obtained for a distinct subset of toluene/NOx reactions in which the integrated oxidant exposure was varied to alter oxidation. The relative volatility of different SOA types displays similar variability and is strongly correlated with SOA oxidation state (OSC). On average, relatively low oxidation and volatility were observed for aliphatic alkene (including terpenes) and n-alkane SOA while the opposite is true for mono- and polycyclic aromatic hydrocarbon SOA. Effective enthalpy for total chamber aerosol obtained from volatility differential mobility analysis is also highly correlated with OSC indicating a primary role for oxidation levels in determining the volatility of chamber SOA. Effective enthalpies for chamber SOA are substantially lower than those of neat organic standards but are on the order of those obtained for partially oligomerized glyoxal and methyl glyoxal. This dataset is associated with the following publication: Docherty, K., E. Corse, M. Jaoui, J. Offenberg, T. Kleindienst, J. Krug, T. Riedel, and M. Lewandowski. Trends in the oxidation and relative volatility of chamber-generated secondary organic aerosol. AEROSOL SCIENCE AND TECHNOLOGY. Taylor & Francis, Inc., Philadelphia, PA, USA, 52(9): 992-1004, (2018).

The relationship between the oxidation state and relative volatility of secondary organic aerosol (SOA) from the oxidation of a wide range of hydrocarbons is investigated using a fast-stepping, scanning thermodenuder interfaced with a high resolution time-of-flight aerosol mass spectrometer (AMS). SOA oxidation state varied widely across the investigated range of parent hydrocarbons but was relatively stable for replicate experiments using a single hydrocarbon precursor. On average, unit mass resolution indicators of SOA oxidation (e.g., AMS f43 and f44) are consistent with previously reported values. Linear regression of H:C vs O:C obtained from parameterization of f43 and f44 and elemental analysis of high resolution spectra in Van Krevelen space both yield a slope of ~0.5 across different SOA types. A similar slope was obtained for a distinct subset of toluene/NOx reactions in which the integrated oxidant exposure was varied to alter oxidation. The relative volatility of different SOA types displays similar variability and is strongly correlated with SOA oxidation state (OSC). On average, relatively low oxidation and volatility were observed for aliphatic alkene (including terpenes) and n-alkane SOA while the opposite is true for mono- and polycyclic aromatic hydrocarbon SOA. Effective enthalpy for total chamber aerosol obtained from volatility differential mobility analysis is also highly correlated with OSC indicating a primary role for oxidation levels in determining the volatility of chamber SOA. Effective enthalpies for chamber SOA are substantially lower than those of neat organic standards but are on the order of those obtained for partially oligomerized glyoxal and methyl glyoxal. This dataset is associated with the following publication: Docherty, K., E. Corse, M. Jaoui, J. Offenberg, T. Kleindienst, J. Krug, T. Riedel, and M. Lewandowski. Trends in the oxidation and relative volatility of chamber-generated secondary organic aerosol. AEROSOL SCIENCE AND TECHNOLOGY. Taylor & Francis, Inc., Philadelphia, PA, USA, 52(9): 992-1004, (2018).

EPA did not generate data as part of this work. This dataset is not publicly accessible because: I personally did not generate any new data in this study. It can be accessed through the following means: Via contact with corresponding author. Format: This study was led by the University of North Carolina at Chapel Hill and they plan to distribute through Mendeley Data. Data is not yet posted. This dataset is associated with the following publication: Schmedding, R., M. Ma, Y. Zhang, S. Farrell, H. Pye, Y. Chen, C. Wang, Q. Rasool, S.H. Budisulistiorini, A. Ault, J. Surratt, and W. Vizuete. α-Pinene-Derived organic coatings on acidic sulfate aerosol impacts secondary organic aerosol formation from isoprene in a box model. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, USA, 213: 456-462, (2019).

EPA did not generate data as part of this work. This dataset is not publicly accessible because: I personally did not generate any new data in this study. It can be accessed through the following means: Via contact with corresponding author. Format: This study was led by the University of North Carolina at Chapel Hill and they plan to distribute through Mendeley Data. Data is not yet posted. This dataset is associated with the following publication: Schmedding, R., M. Ma, Y. Zhang, S. Farrell, H. Pye, Y. Chen, C. Wang, Q. Rasool, S.H. Budisulistiorini, A. Ault, J. Surratt, and W. Vizuete. α-Pinene-Derived organic coatings on acidic sulfate aerosol impacts secondary organic aerosol formation from isoprene in a box model. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, USA, 213: 456-462, (2019).

This research used data mining approaches to better understand factors affecting the formation of secondary organic aerosol (SOA). Although numerous laboratory and computational studies have been completed on SOA formation, it is still challenging to determine factors that most influence SOA formation. Experimental data were based on previous work described by Offenberg et al. (2017), where volume concentrations of SOA were measured in 139 laboratory experiments involving the oxidation of single hydrocarbons under different operating conditions. Three different data mining methods were used, including nearest neighbor, decision tree, and pattern mining. Both decision tree and pattern mining approaches identified similar chemical and experimental conditions that were important to SOA formation. Among these important factors included the number of methyl groups, the number of rings and the presence of dinitrogen pentoxide (N2O5). This dataset is associated with the following publication: Olson, D., J. Offenberg, M. Lewandowski, T. Kleindienst, K. Docherty, M. Jaoui, J.D. Krug, and T. Riedel. Data mining approaches to understanding the formation of secondary organic aerosol. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, USA, 252: 118345, (2021).

This research used data mining approaches to better understand factors affecting the formation of secondary organic aerosol (SOA). Although numerous laboratory and computational studies have been completed on SOA formation, it is still challenging to determine factors that most influence SOA formation. Experimental data were based on previous work described by Offenberg et al. (2017), where volume concentrations of SOA were measured in 139 laboratory experiments involving the oxidation of single hydrocarbons under different operating conditions. Three different data mining methods were used, including nearest neighbor, decision tree, and pattern mining. Both decision tree and pattern mining approaches identified similar chemical and experimental conditions that were important to SOA formation. Among these important factors included the number of methyl groups, the number of rings and the presence of dinitrogen pentoxide (N2O5). This dataset is associated with the following publication: Olson, D., J. Offenberg, M. Lewandowski, T. Kleindienst, K. Docherty, M. Jaoui, J.D. Krug, and T. Riedel. Data mining approaches to understanding the formation of secondary organic aerosol. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, USA, 252: 118345, (2021).

Atmospheric organic aerosol (OA) has important impacts on climate and human health but its sources remain poorly understood. Biogenic monoterpenes and sesquiterpenes are important precursors of secondary organic aerosol (SOA), but the amounts and pathways of SOA generation from these precursors are not well constrained by observations. We propose that the less-oxidized oxygenated organic aerosol (LO-OOA) factor resolved from positive matrix factorization (PMF) analysis on aerosol mass spectrometry (AMS) data can be used as a surrogate for fresh SOA from monoterpenes and sesquiterpenes in the southeastern US. This hypothesis is supported by multiple lines of evidence, including lab-in-the-field perturbation experiments, extensive ambient ground-level measurements, and state-of-the-art modeling. We performed lab-in-the-field experiments in which the ambient air is perturbed by the injection of selected monoterpenes and sesquiterpenes, and the subsequent SOA formation is investigated. PMF analysis on the perturbation experiments provides an objective link between LO-OOA and fresh SOA from monoterpenes and sesquiterpenes as well as insights into the sources of other OA factors. Further, we use an upgraded atmospheric model and show that modeled SOA concentrations from monoterpenes and sesquiterpenes could reproduce both the magnitude and diurnal variation of LO-OOA at multiple sites in the southeastern US, building confidence in our hypothesis. We estimate the annual average concentration of SOA from monoterpenes and sesquiterpenes in the southeastern US to be roughly 2µgm−3. Dataset (csv file) contains CMAQ model predictions for locations in the southeastern US during 2012 and 2013. The species definition file (txt) defines how quantities were obtained from the model. Data in the csv files follows the writesite utility output format (https://github.com/USEPA/CMAQ/tree/5.2.1/POST/writesite). Links to additional datasets are provided. This dataset is associated with the following publication: Xu, L., H. Pye, J. He, Y. Chen, B. Murphy, and N. Ng. Experimental and model estimates of the contributions from biogenic monoterpenes and sesquiterpenes to secondary organic aerosol in the southeastern United States. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, GERMANY, 18(17): 12613-12637, (2018).

Atmospheric organic aerosol (OA) has important impacts on climate and human health but its sources remain poorly understood. Biogenic monoterpenes and sesquiterpenes are important precursors of secondary organic aerosol (SOA), but the amounts and pathways of SOA generation from these precursors are not well constrained by observations. We propose that the less-oxidized oxygenated organic aerosol (LO-OOA) factor resolved from positive matrix factorization (PMF) analysis on aerosol mass spectrometry (AMS) data can be used as a surrogate for fresh SOA from monoterpenes and sesquiterpenes in the southeastern US. This hypothesis is supported by multiple lines of evidence, including lab-in-the-field perturbation experiments, extensive ambient ground-level measurements, and state-of-the-art modeling. We performed lab-in-the-field experiments in which the ambient air is perturbed by the injection of selected monoterpenes and sesquiterpenes, and the subsequent SOA formation is investigated. PMF analysis on the perturbation experiments provides an objective link between LO-OOA and fresh SOA from monoterpenes and sesquiterpenes as well as insights into the sources of other OA factors. Further, we use an upgraded atmospheric model and show that modeled SOA concentrations from monoterpenes and sesquiterpenes could reproduce both the magnitude and diurnal variation of LO-OOA at multiple sites in the southeastern US, building confidence in our hypothesis. We estimate the annual average concentration of SOA from monoterpenes and sesquiterpenes in the southeastern US to be roughly 2µgm−3. Dataset (csv file) contains CMAQ model predictions for locations in the southeastern US during 2012 and 2013. The species definition file (txt) defines how quantities were obtained from the model. Data in the csv files follows the writesite utility output format (https://github.com/USEPA/CMAQ/tree/5.2.1/POST/writesite). Links to additional datasets are provided. This dataset is associated with the following publication: Xu, L., H. Pye, J. He, Y. Chen, B. Murphy, and N. Ng. Experimental and model estimates of the contributions from biogenic monoterpenes and sesquiterpenes to secondary organic aerosol in the southeastern United States. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, GERMANY, 18(17): 12613-12637, (2018).

Oxidation of the monoterpene Δ3-carene (C10H16) is a potentially important and under-studied source of atmospheric secondary organic aerosol (SOA). We present chamber-based measurements of the speciated gas and particle phases during photochemical oxidation of Δ3-carene. We find evidence of highly oxidized organic molecules (HOM) in the gas phase and relatively low volatility SOA dominated by C7-C10 species. We then use computational methods to develop the first stages of a Δ3-carene photochemical oxidation mechanism and explain some of our measured compositions. We find that alkoxy bond scission of the cyclohexyl ring likely leads to efficient HOM formation, in line with previous studies. We also find a surprising role for the abstraction of primary hydrogens from methyl groups, which has been calculated to be rapid in the α-pinene system, and suggest more research is required to determine if this is more general to other systems and a feature of autoxidation. This work develops a more comprehensive view of Δ3-carene photochemical oxidation products via measurements and lays out a suggested mechanism of oxidation via computationally derived rate coefficients. This dataset is not publicly accessible because: Non-EPA data. It can be accessed through the following means: Please contact Joel Thornton at: thornton@atmos.uw.edu. Format: text files. This dataset is associated with the following publication: D'Ambro, E., N. Hyttinen, K. Møller, S. Iyer, R. Otkjær, D. Bell, J. Liu, F. Lopez-Hilfiker, S. Schobesberger, J. Shilling, A. Zelenyuk, H. Kjaergaard, J. Thornton, and T. Kurten. Pathways to highly oxidized products in the Δ3-Carene + OH system. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, USA, 56(4): 2213-2224, (2022).