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List of Abstracts 185P-Observations 2.39 ID:4199 10:30Highly sensitive, rapid in-situ optical NO2 detection for airborne peroxy radical measurementsMarkus Horstjann, Maria Dolores Andrés Hernández, Vladyslav Nenakhov, John P. BurrowsUniversity of Bremen, Institute of Environmental Physics (IUP)Contact: markus.horstjann@iup.physik.uni-bremen.deThe first measurement campaign OMO (Oxidation Mechanisms Observations) of the new high-altitude longrange(HALO) aircraft aims at the study of oxidative processes of the upper troposphere / lower stratosphere(UT/LS region). Here, peroxy radicals (HO2 and RO2, R being an organic chain) are of major importance,and information about their concentration levels is essential to improve our understanding of the mechanismsof chemical processing in the troposphere. One of the techniques to detect the total sum RO2* of peroxyradicals ([RO2*] = [HO2] + [RO2]) is to quickly convert them to NO2 in a chain reaction (PeRCA PeroxyRadical Chemical Amplification). An amplification factor (called chain length CL) of 50-200 can beachieved depending on the ambient pressure; thus typical RO2* upper tropospheric concentrations of 10-50pptv results in the formation of ~0,5-2,5 ppbv NO2. To overcome the limitations of a chemiluminescentdetection scheme using luminol which usually prevents measurements below ambient pressures of less than250 mbar, a novel optical detector based on cavity enhanced absorption spectroscopy (CEAS) and usingoptical feedback has been developed. Resonator calibration with ring-down time acquisition permits directabsorption coefficient measurements. A high finesse V-cavity with 40 cm mirror distance is employed; themirror reflectivity of 99,993% results in an optical path length of 5,7 km. The detector operates with acontinuous gas flow of 1 std.l./min. at a pressure of 100 mbar, which allows the resonator to be flushed witha t90/10 time of three seconds. A NO2 1σ-detection limit of 0,23 ppbv / (Hz)^0,5 (data rate of the detector: 9Hz) is achieved which already allows for peroxy radical detection. However, the use of cavity mirrors withan even higher reflection is possible to boost this limit. A comparison with the previously usedchemiluminescence luminol detector will be presented and both detectors’ performance discussed.P-Observations 2.40 ID:4170 10:30CH4 and N2O emissions from a sphagnum peatland and a fertilized sandy soil using a new portableinfrared laser spectrometerChristophe Guimbaud 1 , Valery Catoire 1 , Sébastien Gogo 2 , Claude Robert 1 , Michel Chartier 1 , LucPomathiod 1 , Fatima Laggoun Défarge 2 , Agnès Grossel 3 , Bernard Nicoullaud 3 , Guy Richard 31 LPC2E UMR 6115 , CNRS et Univ. Orléans2 ISTO UMR 6113 , CNRS et Univ. Orléans3 INRA, UR 0272 OrléansContact: Christophe.Guimbaud@cnrs-orleans.frA new type of portable infra red spectrometer (SPIRIT : SPectromètre Infra-Rouge In situ Troposphérique)using a quantum cascade laser and a patented new long multipass optical cell has been set up for thesimultaneous flux measurements of two Greenhouse Gases (GHG): nitrous oxide (N2O) and methane (CH4),at the air land interface. The basics of the instrument, the data derivation for trace gas concentrationdetermination in the atmosphere, and the chamber method to derive emission fluxes of these GHG fromlands are described. The analytical performances of SPIRIT are tested in two types of lands in Region Centre(France): (i) an anthropogenized sphagnum peatland (Laguette; Neuvy sur Barangeon) characterized byvascular plants invasion (ii) a sandy soil in the site of INRA-Orléans. The ability of SPIRIT to assess withprecision spatial and temporal dependence emissions of these GHG in the field is demonstrated. In additionemission modes (diffusive episodes and bubbling events) can be observed and quantified due to the highfrequency (1 Hz) of the concentration measured. SPIRIT adaptation for detailed process-oriented studies ofGHG flux emissions is also demonstrated by the investigation of emission dependence as a function of bioticiCACGP-IGAC 2010 14 July, 2010