The composition, sources and chemical transformation of volatile organic compounds (VOCs)and organic aerosol (OA) particles were investigated during July–August 2021 at a rural forested site in southwestGermany, 10 km north of the city of Karlsruhe. VOCs and semi-volatile OA particles were measured witha proton-transfer-reaction mass spectrometer coupled to the CHemical Analysis of aeRosols ONline particleinlet (CHARON–PTR-MS). The CHARON-measured OA mass accounted for 62+-18% on average of the totalOA mass (4.2+-2.8 μgm-3) measured concurrently with an aerosol mass spectrometer (AMS). The total concentrationsof measured VOCs ranged from 7.6 to 88.9 ppb with an average of 31.2+-13.4 ppb. Positive matrixfactorization (PMF) was used to identify major source factors of VOCs and OA particles. Three types of oxygenatedVOC (OVOC), namely aromatic OVOCs, biogenic OVOCs and aged OVOCs, contributed on average11%+-9 %, 37%+-29% and 29%+-21% of total VOC concentrations, respectively. The results of AMS–PMFindicated substantial contributions of oxygenated organic compounds to OA particle mass. Three secondary OA(SOA) factors determined by CHARON–PMF analysis, namely aromatic SOA (5%7 %), daytime biogenicSOA (17%+-17 %) and nighttime biogenic SOA (28%+-21 %), consistently showed high contributions to thetotal CHARON-measured OA mass. Nighttime particle growth was observed regularly in this area, which wasmainly attributed to the semi-volatile organic compounds and organic nitrates formed from the oxidation ofmonoterpenes and sesquiterpenes. This study presents the major sources, real-time transformations of VOCs andOA particles, and nighttime particle formation characteristics for central European forested areas.

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Brown carbon aerosol (BrC) is one major contributor to atmospheric air pollution in Europe, especially in winter. Therefore, we studied the chemical composition, diurnal variation, and sources of BrC from 17th February to 16th March at a rural location in southwest Germany. In total, 178 potential BrC molecules (including 7 nitro aromatic compounds, NACs) were identified in the particle phase comprising on average 63 ± 32 ng m−3, and 31 potential BrC (including 4 NACs) molecules were identified in the gas phase contributing on average 6.2 ± 5.0 ng m−3 during the whole campaign. The 178 potential BrC molecules only accounted for 2.3 ± 1.5 % of the total organic mass, but can explain 11 ± 11 % of the total BrC absorption at 370 nm, assuming an average mass absorption coefficient at 370 nm (MAC370) of 9.5 m2 g−1. A few BrC molecules dominated the total BrC absorption. In addition, diurnal variations show that gas phase BrC was higher at daytime and lower at night. It was mainly controlled by secondary formation (e.g. photooxidation) and particle-to-gas partitioning. Correspondingly, the particle phase BrC was lower at daytime and higher at nighttime. Secondary formation dominates the particle-phase BrC with 61 ± 21 %, while 39 ± 21 % originated from biomass burning. Furthermore, the particle-phase BrC showed decreasing light absorption due to photochemical aging. This study extends the current understanding of real-time behaviors of brown carbon aerosol in the gas and particle phase at a location characteristic for the central Europe.

Spektren der Lichtquelle in der AIDA Aerosol und Wolkenkammer

We investigated secondary organic aerosol (SOA) from β-caryophyllene oxidation generated over 213-313 K from ozonolysis. Positive matrix factorization (PMF) was used to deconvolute the desorption data (thermograms) of SOA products detected by a chemical ionization mass spectrometer (FIGAERO-CIMS). A non-monotonic dependence of particle volatility (saturation concentration at 298 K, C_298K^*) on formation temperature (213-313 K) was observed, primarily due to temperature-dependent formation pathways of β-caryophyllene oxidation products. The PMF analysis grouped detected ions into 11 compound groups (factors) with characteristic volatility. These compound groups act as indicators for the underlying SOA formation mechanisms. Their different temperature response revealed that the relevant chemical pathways (e.g., autoxidation, oligomer formation, and isomer formation) had distinct optimal temperatures between 213–313 K, significantly beyond the effect of temperature-dependent partitioning. Furthermore, PMF-resolved volatility groups were compared with volatility basis set (VBS) distributions based on different vapor pressure estimation methods. The variation of the volatilities predicted by different methods is affected by highly oxidation oxygenated molecules, isomers and thermal decomposition of oligomers with long carbon chains. This work distinguishes multiple isomers and identifies compound groups of varying volatility, providing new insights into the temperature-dependent formation mechanisms of β-caryophyllene-derived SOA particles.

The data in the Excel file is related to the publication Gao et al., ACP, 2022. Each sheet of the Excel file corresponds to one plot in the publication. The data originates mainly from FIGAERO-CIMS and HR-ToF-AMS (both Aerodyne Inc.) measurements. “Kinetics, SOA yields and chemical composition of secondary organic aerosol from β-caryophyllene ozonolysis with and without nitrogen oxides between 213 and 313 K” Linyu Gao1,2; Junwei Song1,2; Claudia Mohr3; Wei Huang4; Magdalena Vallon1; Feng Jiang1,2; Thomas Leisner1,5; and Harald Saathoff1 1 Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany 2 Institute of Geography and Geoecology, Working Group for Environmental Mineralogy and Environmental System Analysis, Karlsruhe Institute of Technology, Karlsruhe, Germany 3 Department of Environmental Science, Stockholm University, Stockholm, Sweden 4 Institute for Atmospheric and Earth System Research / Physics, Faculty of Science, University of Helsinki, Helsinki, Finland 5 Institute of Environmental Physics, Heidelberg University, Heidelberg, Germany Correspondence to: Linyu Gao ([email protected]) and Dr. Harald Saathoff ([email protected]) Atmos. Chem. Phys. Discuss. [preprint], https://doi.org/10.5194/acp-2021-1067, in review, 2022. (accepted on April 4th, 2022)

The data in the Excel files are related to the publication Jiang et al., ACP, 2022. Each sheet of the Excel files corresponds to one plot in the publication as repeated below. The data originates mainly from Aqualog and FIGAERO-CIMS measurements. The figures and captions from the publication are shown in the following to allow for a good understanding of the data files. Jiang, F., Song, J., Bauer, J., Gao, L., Vallon, M., Gebhardt, R., Leisner, T., Norra, S., and Saathoff, H.: Chromophores and chemical composition of brown carbon characterized at an urban kerbside by excitation-emission spectroscopy and mass spectrometry, Atmos. Chem. Phys. Discuss. [preprint], https://doi.org/10.5194/acp-2022-465, in review, 2022.