Volatile organic compounds (VOCs) are important for global air quality and oxidation processes in the troposphere. In addition to ground-based measurements, the chemical evolution of such species during transport can be studied by performing in situ airborne measurements. Generally, aircraft instrumentation needs to be sensitive, robust and sample at higher frequency than ground-based systems while their construction must comply with rigorous mechanical and electrical safety standards. Here, we present a new System for Organic Fast Identification Analysis (SOFIA), which is a custom-built fast gas chromatography–mass spectrometry (GC-MS) system with a time resolution of 2–3 min and the ability to quantify atmospheric mixing ratios of halocarbons (e.g. chloromethanes), hydrocarbons (e.g isoprene), oxygenated VOCs (acetone, propanal, butanone) and aromatics (e.g. benzene, toluene) from sub-ppt to ppb levels. The relatively high time resolution is the result of a novel cryogenic pre-concentration unit which rapidly cools (∼ 6 °C s−1) the sample enrichment traps to −140 °C, and a new chromatographic oven designed for rapid cooling rates (∼ 30 °C s−1) and subsequent thermal stabilization. SOFIA was installed in the High Altitude and Long Range Research Aircraft (HALO) for the Oxidation Mechanism Observations (OMO) campaign in August 2015, aimed at investigating the Asian monsoon pollution outflow in the tropical upper troposphere. In addition to a comprehensive instrument characterization we present an example monsoon plume crossing flight as a case study to demonstrate the instrument capability. Hydrocarbon, halocarbon and oxygenated VOC data from SOFIA are compared with mixing ratios of carbon monoxide (CO) and methane (CH4), used to define the pollution plume. By using excess (ExMR) and normalized excess mixing ratios (NEMRs) the pollution could be attributed to two air masses of distinctly different origin, identified by back-trajectory analysis. This work endorses the use of SOFIA for aircraft operation and demonstrates the value of relatively high-frequency, multicomponent measurements in atmospheric chemistry research.

Environmental Context. In the upper troposphere, sources of HOx such as acetone, peroxides, and aldehydes can play an important role in governing the production and destruction of ozone. Convection (over both land and sea) carries gases that can contribute to increased levels of HOx to the upper troposphere. The chemical impact of convection on the continental upper troposphere over Europe is studied by sampling the upper troposphere. Mass spectrometry techniques are used to analyze the collected samples. Such a study should aid in understanding the impact meteorological events have on atmospheric chemistry. Abstract. The volume mixing ratios of several organic trace gases and ozone (O3) were measured in the upper troposphere over Europe during the UTOPIHAN-ACT aircraft campaign in July 2003. The organic trace gases included alkanes, isoprene, aromatics, iodomethane, and trichloroethylene, oxygenates such as acetone, methanol, formaldehyde, carbon monoxide, and longer-lived tracer species such as chlorofluorocarbons and halochloroflurocarbons. The aim of the UTOPIHAN-ACT project was to study the chemical impact of deep convection on the continental upper troposphere. A Lear Jet aircraft, based in Germany, was flown at heights between 6 and 13 km in the region 59°N–42°N to 7°W–13°E during July 2003. Overall, the convectively influenced measurements presented here show a weaker variability lifetime dependence of trace gases than similar measurements collected over the Mediterranean region under more stable high-pressure conditions. Several cases of convective outflow are identified by the elevated mixing ratios of organic species relative to quiescent background conditions, with both biogenic and anthropogenic influences detectable in the upper troposphere. Enhancement at higher altitudes, notably of species with relatively short chemical lifetimes such as benzene, toluene, and even isoprene indicates deep convection over short timescales during summertime. The impact of deep convection on the local upper tropospheric formaldehyde and HOx budgets is assessed.

AbstractDie Zersetzung von Cumolhydroperoxyd durch Schwefelsäure verläuft in äquimolaren Phenol‐Aceton‐Gemischen nach einem Geschwindigkeitsgesetz mit einer Aktivierungsenergie von 18,2 kcal/Mol. Die Reaktionsenthalpie der Zersetzung beträgt für Cumolhydroperoxyd in Phenol/Aceton 53,5 ± 1,0 kcal/Mol, für sec.‐Butyl‐benzolhydroperoxyd in Phenol/Aceton 50,5 ± 1,4 kcal/Mol. Weder bei reinem Cumolhydroperoxyd noch bei reinem sec.‐Butylbenzolhydroperoxyd konnte Acetophenon als Nebenprodukt der Zersetzung nachgewiesen werden.Verschiedene Sauerstoffverbindungen, insbesondere Wasser, hemmen die Säurezersetzung des Cumolhydroperoxyds stark.

AbstractDie Monohydroperoxyde der drei isomeren Xylole und des Äthylbenzols wurden durch Autoxydation der Kohlenwasserstoffe hergestellt, ihre Zersetzung unter den Bedingungen der technischen Autoxydation, d. h. bei Temperaturen um 135°, in Gegenwart von Co‐Stearat als Katalysator und in einem Kohlenwasserstoff als Lösungsmittel lieferte vorwiegend Verbindungen mit unverändertem Kohlenstoffgerüst. Aus der Analyse der bei der Zersetzung entstehenden Gase konnte auf einen geringfügigen Abbau des Kohlenstoffgerüstes durch CC‐Spaltung intermediär auftretender Radikale geschlossen werden. Molekularer Wasserstoff entstand bei der durch Co‐Salze katalysierten Zersetzung der untersuchten Hydroperoxyde nur in sehr geringem Maße.