The effect of acidity and relative humidity on bulk isoprene aerosol parameters has been investigated in several studies, however few measurements have been conducted on individual aerosol compounds. The focus of this study has been the examination of the effect of acidity and relative humidity on secondary organic aerosol (SOA) chemical composition from isoprene photooxidation in the presence of nitrogen oxide (NOx). A detailed characterization of SOA at the molecular level was also investigated. Experiments were conducted in a 14.5 m3 smog chamber operated in flow mode. Based on a detailed analysis of mass spectra obtained from gas chromatography-mass spectrometry of silylated derivatives in electron impact and chemical ionization modes, and ultra-high performance liquid chromatography/electrospray ionization/time-of-flight high resolution mass spectrometry, and collision-induced dissociation in the negative ionization modes, we characterized not only typical isoprene products, but also new oxygenated compounds. A series of nitroxy-organosulfates (OS) were tentatively identified on the basis of high resolution mass spectra. Under acidic conditions, the major identified compounds include 2-methyltetrols (2MT), 2-methylglyceric acid (2MGA) and 2MT-OS. Other products identified include epoxydiols, mono- and dicarboxylic acids, other organic sulfates, and nitroxy- and nitrosoxy-OS. The contribution of SOA products from isoprene oxidation to PM2.5 was investigated by analysing ambient aerosol collected at rural sites in Poland. Methyltetrols, 2MGA and several organosulfates and nitroxy-OS were detected in both the field and laboratory samples. The influence of relative humidity on SOA formation was modest in non-acidic seed experiments, and stronger under acidic seed aerosol. Total secondary organic carbon decreased with increasing relative humidity under both acidic and non-acidic conditions. While the yields of some of the specific organic compounds decreased with increasing relative humidity others varied in an indeterminate manner from changes in the relative humidity. This dataset is associated with the following publication: Nestorowicz, K., M. Jaoui, K. Rudzinski, M. Lewandowski, T. Kleindienst, G. Spolnik, W. Danikiewicz, and R. Szmigielski. Chemical Composition of Isoprene SOA Under Acidic and Non-Acidic Conditions: Effect of Relative Humidity. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, GERMANY, 18(4): 18101-18121, (2018).

Indoor chamber and filter extraction experimental details, E-AIM II model results, RPLC(−) and HILIC/(−)ESI-HR-QTOF instrument conditions and oxidation product spectra, SOA yield comparison at varying acidity, HR-TOF-CIMS instrument conditions and oxidation product spectra, proposed MS fragmentation of selected oxidation tracers, SOA yield calculations. This dataset is associated with the following publication: Fruenheim, M., J. Offenberg, Z. Zhang, J.D. Surratt, and A. Gold. Chemical Composition of Secondary Organic Aerosol Formed from the Oxidation of Semivolatile Isoprene Epoxydiol Isomerization Products. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, USA, 58(51): 22571-22582, (2024).

Dataset contains information displayed in figures 1-4 and abstract/table of contents figure. This dataset is associated with the following publication: Budisulistiorini, S., A. Nenes, A. Carlton, J. Surratt, V.F. McNeill, and H. Pye. Simulating Aqueous-Phase Isoprene-Epoxydiol (IEPOX) Secondary Organic Aerosol Production During the 2013 Southern Oxidant and Aerosol Study (SOAS). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, USA, 51(9): 5026-5034, (2017).

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).

Dataset contains supplementary information (model inputs and/or outputs and literature values) for Section 4.1 (idealized acidity calculations), Section 4.2 (box model calculations of pH for ambient conditions), Section 7.1 (observed aerosol pH values), Section 7.2 (observed cloud pH values), and Section 8.1 (CMAQ hemispheric predictions). This dataset is associated with the following publication: Pye, H., A. Nenes, B. Alexander, A. Ault, M. Barth, S. Clegg, J. Collett, K. Fahey, C. Hennigan, H. Herrmann, M. Kanakidou, J. Kelly, I. Ku, V.F. McNeill, N. Riemer, T. Schaefer, G. Shi, A. Tilgner, J. Walker, T. Wang, R. Weber, J. Xing, R. Zaveri, and A. Zuend. The Acidity of Atmospheric Particles and Clouds. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, GERMANY, 20(8): 4809–4888, (2020).

Dataset contains supplementary information (model inputs and/or outputs and literature values) for Section 4.1 (idealized acidity calculations), Section 4.2 (box model calculations of pH for ambient conditions), Section 7.1 (observed aerosol pH values), Section 7.2 (observed cloud pH values), and Section 8.1 (CMAQ hemispheric predictions). This dataset is associated with the following publication: Pye, H., A. Nenes, B. Alexander, A. Ault, M. Barth, S. Clegg, J. Collett, K. Fahey, C. Hennigan, H. Herrmann, M. Kanakidou, J. Kelly, I. Ku, V.F. McNeill, N. Riemer, T. Schaefer, G. Shi, A. Tilgner, J. Walker, T. Wang, R. Weber, J. Xing, R. Zaveri, and A. Zuend. The Acidity of Atmospheric Particles and Clouds. Atmospheric Chemistry and Physics. Copernicus Publications, Katlenburg-Lindau, GERMANY, 20(8): 4809–4888, (2020).

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).

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).