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 (NO x ). A detailed characterization of SOA at the molecular level was also investigated. Experiments were conducted in a 14.5 m 3 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, ultra-high performance liquid chromatography/electrospray ionization/time-of-flight highresolution 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 (NOSs) 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 PM 2.5 was investigated by analyzing 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.

Highly oxygenated molecules (HOMs) are a class of compounds associated with secondary organic aerosols exhibiting high oxygen to carbon (O:C) ratios and often originating from the oxidation of biogenic compounds. Here, the photooxidation and ozonolysis of isoprene were examined under a range of conditions to identify HOM tracers for aged isoprene aerosol. The HOM tracers were identified as silylated derivatives by gas chromatography–mass spectrometry and by detecting their parent compounds by liquid chromatography–high resolution mass spectrometry. In addition to the previously observed methyltetrols and 2-methylglyceric acid, seven tracer compounds were identified, including 2-methyltartronic acid (MTtA), 2-methylerythronic acid (2MeTrA), 3-methylerythronic acid (3MeTrA), 2-methylthreonic acid (2MTrA), 3-methylthreonic acid (3MTrA), erythro-methyltartaric acid (e-MTA), and threo-methyltartaric acid (t-MTA). The molecular structures were confirmed with authentic standards synthesized in the laboratory. The presence of some of these HOMs in the gas and particle phases simultaneously provides evidence of their gas/particle partitioning. To determine the contributions of aged isoprene products to ambient aerosols, we analyzed ambient PM2.5 samples collected in the southeastern United States in summer 2003 and at two European monitoring stations located in Zielonka and Godów (Poland). Our findings show that methyltartaric acids (MTA) and 2- and 3-methylthreonic acids (and their stereoisomers) are representative of aged isoprene aerosol because they occur both in the laboratory chamber aerosol obtained and in ambient PM2.5. On the basis of gas chromatography–mass spectrometry (GC-MS) analysis, their concentrations were found to range from 0.04 ng for 3-methylthreonic acid to 6.3 ng m–3 for methyltartaric acid at the southeast site in Duke Forest, NC, USA.

Green plants exposed to abiotic or biotic stress release C-5 and C-6 unsaturated oxygenated hydrocarbons called Green Leaf Volatiles (GLVs). GLVs partition into tropospheric waters and react to form secondary organic aerosol (SOA). We explored the kinetics of aqueous-phase reactions of 1-penten-3-ol (PENTOL), (Z)-2-hexen-1-ol (HEXOL), and (E)-2-hexen-1-al (HEXAL) with SO4 •–, •OH, and NO3 •. At 298 K, the rate constants for reactions of PENTOL, HEXOL, and HEXAL with SO4 •– were, respectively, (9.4 ± 1.0) × 108 L mol–1 s–1, (2.5 ± 0.3) × 109 L mol–1 s–1, and (4.8 ± 0.2) × 108 L mol–1 s–1; with •OH – (6.3 ± 0.1) × 109 L mol–1 s–1, (6.7 ± 0.3) × 109 L mol–1 s–1, and (4.8 ± 0.3) × 109 L mol–1 s–1; and with NO3 • – (1.5 ± 0.15) × 108 L mol–1 s–1, (8.4 ± 2.3) × 108 L mol–1 s–1, and (3.0 ± 0.7) × 107 L mol–1 s–1. The rate constants increased weakly with temperatures ranging from 278 to 318 K. The diffusional limitations of the rate constants appeared significant only for the GLV–•OH reactions. The aqueous-phase reactions appeared negligible in deliquescent aerosol and haze water but not in clouds and rains. The atmospheric lifetimes of GLVs decreased from many days to hours with increasing liquid water content and radicals’ concentration.

Abstract. 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. While the focus of this study 10 has been the examination of the effect of acidity and RH on secondary organic aerosol (SOA) chemical composition from isoprene photooxidation in the presence of NOx, a detailed characterization of SOA at the molecular level have been also conducted. Experiments were conducted in a 14.5 m 3 smog chamber operated in flow mode. Based on a detailed analysis of mass spectra obtained from GCMS of silylated derivatives in EI and CI modes, and UPLC/ESI/QTOF HRMS, and collision-induced dissociation in the positive and negative ionization modes, we characterized not only 15 typical isoprene products, but also new oxygenated compounds. The analysis showed the presence of methylthreonic acids (mTr) and methyltartaric acids (mTA), proposed recently by our groups as isoprene aging SOA markers. Furthermore, a series of organosulfates (OSs) were tentatively identified including 2mTr-OS, 2mTA-OS and 2mTA nitroxy-OS. 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, OSs, and nitroxy-and 20 nitrosoxy-OSs. The contribution of SOA products from isoprene oxidation to PM2.5 was investigated by analyzing ambient aerosol collected at rural sites in Poland. mTs, mGA and several organosulfates and nitroxy-OS were detected in both the field and laboratory samples. The influence of RH on SOA formation was modest in non-acidic seed experiments. Total SOC decreased with increasing RH. The yields of most compounds decreased, but the concentrations of 2mTA, IEPOX-OS, 2mGA-OS and 2mTr-OS increased with increasing RH. Some components followed this pattern while other were more 25 abundant in non-acidic experiments or behaved in a mixed way, depending on RH.

Figure S1. Relative amounts of aerosol components detected with GC-MS acidic seed (pink) and nonacidic seed (yellow) experiments (the areas of the circles are proportional to the estimated mass concentrations of compounds).

No abstract

<p><strong>Introduction</strong><br> Numerous green leaf volatiles (GLVs) are released into the atmosphere due to the stress, cell damage or wounding. Fog forming over vegetation takes up these compounds, promoting their aqueous-phase oxidation to less volatile compounds. The droplets eventually dry out, leaving behind the secondary organic aerosol (SOA). These pathways are still poorly recognized as potentially novel routes for the formation of atmospheric SOA. Kinetic investigations of GLVs in the gas phase have already been reported by Shalamzari et. al. 2014, Davis et. al. 2011 and many others, while there is no kinetic data on the aqueous phase reactions of selected C6 and C5 GLVs. In the present study, we focussed on the kinetic studies of GLVs with the hydroxyl, sulfate and nitrate radicals as a possible source of aqueous SOA.</p><p><strong>Experimental method</strong><br> The rate constants of reactions of GLVs with atmospherically relevant radicals were studied using a laser flash photolysis-laser long path absorption (LFP-LLPA). Kinetic investigations of GLVs with hydroxyl radicals were performed using competition kinetics, where H<sub>2</sub>O<sub>2</sub> (2 x 10<sup>-4</sup> mol L<sup>-1</sup>) was used as a radical precursor and KSCN (2 x 10<sup>-5</sup> mol L<sup>-1</sup>) as a reference compound. The method is similar to that introduced by Behar, et al. 1972. Kinetic measurements of sulfate and nitrate radicals with GLVs, were done using a direct flash photolysis method, where sodium persulfate (5 x 10<sup>-4</sup> mol L<sup>-1</sup>) was the precursor in the generation of SO<sub>4</sub><sup>•ꟷ</sup> and sodium nitrate (1 x 10<sup>-1</sup> mol L<sup>-1</sup>) and sodium sulfate (3 x 10<sup>-2</sup> mol L<sup>-1</sup>) were the precursor for the generation of nitrate radicals.</p><p><strong>Conclusions</strong><br> In the present study, we explored the kinetics of aqueous-phase reactions of three GLVs- 1-penten-3-ol, cis-2-hexen-1-ol and 2-E-hexenal - with atmospheric radicals SO<sub>4</sub><sup>•ꟷ</sup>, <sup>•</sup>OH and NO<sub>3</sub><sup>•</sup>. The second-order rate constants were determined for a temperature range of 278 K to 318 K. A weak temperature dependence was observed for the aqueous-phase kinetics of all three GLVs with selected atmospherically relevant radicals. To explain the weak temperature dependence of aqueous-phase reaction of GLVs with atmospheric radicals, rate constants were investigated for the diffusion limitation. The atmospheric significance of the aqueous-phase reaction was evaluated, by calculating aqueous-phase lifetime and their relative rate to the gas phase reactions with respective radicals, which clearly demonstrated their importance above the gas-phase reactions in tropospheric aqueous-phase. The present work is a part of the bigger research project on the aqueous-phase reactions of a series of atmospherically relevant GLVs whereas a next step oxidation products in the aqueous-phase are being investigated at a present stage. </p><p>This project is supported by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 711859 and by financial resources for science in the years 2017-2021 awarded by the Polish Ministry of Science and Higher Education for the implementation of an international co-financed project. The research project was also partially supported by funding under Project CREATE of European Union’s H2020 and ERASMUS PLUS staff mobility programme.</p>

The market of pharmaceutical products is offering a wide range of supplements. Most of the consumers believe that these products will improve their state of health, but are they getting what they want and what they are paying for? The aim of the study was to evaluate the quality of selected dietary supplements containing conjugated linoleic acid (CLA). All supplements were available in the Warsaw markets and bought from pharmacies. Assessment of the quality of food supplements was achieved by analysis of fatty acid using gas chromatography coupled with a mass spectrometer. On the basis of the investigations carried out, it was found that content of CLA in selected dietary supplements ranged between 282 and 528 mg by weight of a single capsule. The content of bioactive ingredients found in three of the four product supplements assessed was lower than was claimed by the manufacturer.