Ketolimonene (4-acetyl-1-methylcyclohexene, C 9 H 14 O) is a first-generation reaction product in the gas-phase oxidation of limonene by OH radical and, to a lesser extent, O 3 .Molar yields between 4.9% and 39% were measured in the gas phase from limonene + OH [1-4] and < 4% from limonene + O 3 [2].Yet, ketolimonene reactivity in the atmosphere is poorly known, with only one determination of the OH rate constant and two determinations for the O 3 one [5,6], the latter two disagreeing by a factor of almost 2. No data on reaction products are available and only one study deals with secondary organic aerosol (SOA) formation from the ozonolysis reaction [6].The objectives of the present study were to determine the O 3 kinetics and investigate the related gas-and particle-phase reaction products and potential SOA formation.The 760-L quartz chamber at "Al.I. Cuza" Iasi University (ESC-Q-UAIC) was used together with long-path Fourier Transform infrared spectroscopy, proton-transfer mass spectrometry (PTR-MS) coupled to a CHARON inlet, selected ion mass spectrometry (SYFT-MS) and scanning mobility particle sizer (SMPS).The results will be discussed in terms of atmospheric lifetime, ozone reaction mechanism and SOA yields.
<p>Atmospheric transformation processes have been extensively studied in the laboratory using simulation chambers with various designs and materials. These tools allow &#160;kinetic experiments to be performed under well-controlled conditions whereby a selected volatile organic compound (VOC) is usually oxidized in synthetic air. While atmospheric chambers are invaluable to provide kinetic parameters that are needed in atmospheric chemical mechanisms, their limitation is that they do not test these chemical mechanisms under conditions that are representative of the complex atmosphere, i.e. containing multiple VOCs and inorganic species.</p><p>In the present work, a mobile rectangular atmospheric simulation chamber of ~ 9 m<sup>3</sup>, made of Teflon FEP foils, was built at IMT Lille Douai for laboratory and field studies. The whole setup &#8211; called DouAir &#8211; can be easily disassembled, transported and deployed in the field. This new tool allows trapping of real air masses on-site, providing observations on the fate of reactive trace gases, which when compared to box model simulations can provide a critical test of our understanding of atmospheric chemistry. The chamber allows both solar and artificial irradiation, the irradiance being monitored by spectroradiometry. The chamber is equipped with a large array of analytical instruments, including PTR-ToFMS and GC-MS for VOC measurements, CRM for total OH reactivity, PERCA for peroxy radicals, O<sub>3</sub> and NO<sub>x</sub> analyzers, and SMPS for aerosols. Here we describe the DouAir setup and will discuss characterization experiments carried out to validate the chamber. DouAir was tested for the first time during an intensive field campaign in the Landes forest (France) during summer 2018: CERVOLAND (Characterization of Emissions and Reactivity of Volatile Organic Compounds in the Landes Forest). Examples of experiments performed during CERVOLAND will be presented.</p>
<p>Nitrous acid (HONO) is one of the important atmospheric trace gases due to its contribution to the cycles of nitrogen oxides (NOx) and hydrogen oxides (HOx). In particular it acts as a precursor of tropospheric OH radicals, which is responsible for the self-cleansing capacity of the atmosphere [1,2]. We developed an instrument based on incoherent broadband cavity enhanced absorption spectroscopy (IBBCEAS) for automatic measurement of HONO in a rural area in a summer period during a field "Campagne d&#8217;OBservation Intensive des Ae&#769;rosols et pre&#769;curseurs a&#768; Caillou&#235;l-Cr&#233;pigny (COBIACC)" in France. IBBCEAS technique is now extensively used in field applications for the measurements of both trace gases and aerosols [3,4].</p><p>Real-time in situ measurements of HONO and NO<sub>2</sub> have been simultaneously carried out. The IBBCEAS instrument performance has been demonstrated and validated through lab-based tests, and in particular through field intercomparison via side-by-side measurements of temporal concentration profiles of HONO and NO<sub>2</sub> in the rural area. The intercomparison of the concentration measurements between IBBCEAS and an instrument called MARGA (Monitor for AeRosols and Gases in Ambient air) for HONO, and IBBCEAS vs. a reference NOx analyzer for NO<sub>2</sub>. Good agreements have been observed which demonstrated the performance of the developed IBBCEAS instrument for the measurement of atmospheric HONO concentration (<5 ppb) in a rural area.</p><p>The preliminary experimental results will be presented and discussed.</p><p><strong>Acknowledgments</strong> This work was supported by the CPER CLIMIBIO program and the Labex CaPPA project (ANR-10-LABX005). The authors highly appreciate the offers of Mr. Eric Wetzels from Polyfluor Plastics bv for the help in our instrumental conception involving Teflon pipe.</p><p><strong>References</strong></p><p>[1] X. Li, T. Brauers, R. H&#228;seler, R. Bohn, H. Fuchs, A. Hofzumahaus, F. Holland, S. Lou, et al., Exploring the atmospheric chemistry of nitrous acid (HONO) at a rural site in Southern China, Atmos. Chem. Phys. <strong>12</strong> (2012) 1497-1513.</p><p>[2] H. Su, Y. Cheng, M. Shao, D. Gao, Z. Yu, L. Zeng, J. Slanina, et al., Nitrous acid (HONO) and its daytime sources at a rural site during the 2004 PRIDE&#8208;PRD experiment in China, J. Geophys. Res. <strong>113</strong> (2008) D14312.</p><p>[3] T. Wu, Q. Zha, W. Chen, Z. Xu, T. Wang, X. He, Development and deployment of a cavity enhanced UV-LED spectrometer for measurements of atmospheric HONO and NO<sub>2</sub> in Hong Kong, Atmos. Environ. <strong>95</strong> (2014) 544-551.</p><p>[4] L. Meng, G. Wang, P. Augustin, M. Fourmentin, Q. Gou, E. Fertein, T. N. Ba, C. Coeur, A. Tomas, W. Chen, Incoherent broadband cavity enhanced absorption spectroscopy-based strategy for direct measurement of aerosol extinction in lidar blind zone, Opt. Lett. <strong>45 </strong>(2020) 1611-1614.</p>
