Hydroxyl Radical, Singlet Oxygen, and Oxidized Product Formation in Photoaged Quinones and Combustion-derived Particles
Description
Data sets used for the study 'The Photochemistry of Quinones and Combustion-derived Particles in Forming Hydroxyl Radicals and Singlet Oxygen in the Atmosphere' by Desiree J. Sarmiento and Dr. Brian J. Majestic from the University of Denver in Denver, Colorado, USA. These sets include HPLC data for determining hydroxyl radical and singlet oxygen concentrations observed from the photoaging of combustion-derived particles (CDPs), quinones, and anthracene in the aqueous phase; HPLC data for the product formation in photoaged 1,4-naphthoquinone (1,4-NAPQ) and photoaged juglone; and GC-MS data of photoaged 1,4-anthraquinone (1,4-ANTQ) and 1,4-NAPQ samples. The CDP samples investigated in this work are hexane CDPs (hx-CDP), ethanol-hx-CDPs (EtOH-hx-CDPs), and iron pentacarbonyl-hx-CDPs (Fe(CO)5-hx-CDPs). The hydroxyl radical concentration per particle mass and the singlet oxygen concentration per particle (See Steps to reproduce) were plotted over the photolysis time to visualize the formation behavior of these species over the course of the photoaging of CDPs, quinones, and anthracene. Files of the MATLAB Curve Fitter results that describe these plots are also provided. All the data obtained support my hypothesis that in sunlit, cloud-water environments, polycyclic aromatic hydrocarbons (PAHs), which are byproducts from incomplete combustion, can oxidize into photosensitizers (light-absorbing compounds that undergo excitation to the singlet and triplet states). These photosensitizers can then partake in radical reactions to form singlet oxygen and catalyze hydroxyl radicals, which result in excess reactive oxygen species (ROS) in the atmosphere.
Files
Steps to reproduce
HPLC data for the photoaged particle suspensions was obtained using the Agilent 1220 Infinity II and the Agilent 1100 LC and DAD systems, wherein the conditions described in Haynes et al. 2019 were used for detecting the photooxidation products, the conditions described in Runberg et al. 2022 were used for detecting para-hydroxybenzoic acid (p-HBA) for hydroxyl radical monitoring, and the conditions described in Le Bechec et al. 2018 were used for detection furfuryl alcohol (FFA) for singlet oxygen monitoring. Calibration curves that relate the analyte concentration to its peak area were prepared to determine the concentrations of p-HBA, FFA, and some of the photooxidation products (in particular, quinones). The hydroxyl radical concentrations were determined using the same method described by Runberg and Majestic 2022 and Araki and Faust 1998. Briefly, sodium benzoate was used to chemically probe for hydroxyl radicals in the sample suspension, and the peak area of its product (para-hydroxybenzoic acid) was used to calculate the hydroxyl radical concentration at each timepoint of the photolysis. The singlet oxygen concentrations were determined using a similar method as Leresche et al. 2019, Li et al. 2019, and Manfrin et al. 2019. Briefly, furfuryl alcohol was used to probe for singlet oxygen in the sample suspension, and its depletion over time was used to calculate the singlet oxygen concentration at each timepoint of the reaction. Because this work was the first to investigate the formation kinetics of singlet oxygen in an aqueous suspension, the rate of FFA loss was calculated using the difference between the initial reaction time (0 minutes) and the amount time the sample was photoaged (See file named Hydroxyl Radical and Singlet Oxygen Calculations). To provide an accurate comparison of the different particle samples, hydroxyl radical and singlet oxygen concentrations were normalized by the particle mass used to make the sample suspension. HPLC data and calculations for hydroxyl radical and singlet oxygen concentrations were recorded and done on Microsoft Excel. GC-MS data for sample chromatograms, which was obtained using the Agilent 5977B GC/MSD, was also recorded on Microsoft Excel. For analysis and compound identification, GC-MS data (data file folders ending in .D) was viewed using the Agilent MassHunter Qualitative Analysis Navigator (B.08.00) and the NIST MS Search (2.3). Plots of the ROS concentration per particle mass as a function of photolysis time, as well as plots of all the chromatograms, were prepared using MATLAB. Data for the linear and logarithmic fits of ROS concentration per particle mass over photolysis time were obtained using the Curve Fitter application on MATLAB. The Curve Fitter files provided can be opened and viewed in Curve Fitter on MATLAB.