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  • × Max Planck Institute for Chemistry, Mainz, Germany
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来源:Atmospheric Chemistry and Physics

作者:S. Borrmann;M. Beekmann;Y. Morille;等

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During July 2009, a one-month measurement campaign was performed in themegacity of Paris. Amongst other measurement platforms, three stationarysites distributed over an area of 40 km in diameter in the greater Parisregion enabled a detailed characterization of the aerosol particle and gasphase. Simulation results from the FLEXPART dispersion model were used todistinguish between different types of air masses sampled. It was found thatthe origin of air masses had a large influence on measured massconcentrations of the secondary species particulate sulphate, nitrate,ammonium, and oxygenated organic aerosol measured with the Aerodyne aerosolmass spectrometer in the submicron particle size range: particularly highconcentrations of these species (about 4 μg m−3, 2 μg m−3,2 μg m−3, and 7 μg m−3,respectively) were measured when aged material was advected from continentalEurope, while for air masses originating from the Atlantic, much lower massconcentrations of these species were observed (about 1 μg m−3, 0.2 μg m−3, 0.4 μg m−3, and1–3 μg m−3, respectively). For the primary emissiontracers hydrocarbon-like organic aerosol, black carbon, and NOx it wasfound that apart from diurnal source strength variations and proximity toemission sources, local meteorology had the largest influence on measuredconcentrations, with higher wind speeds leading to larger dilution andtherefore smaller measured concentrations. Also the shape of particle sizedistributions was affected by wind speed and air mass origin.Quasi-Lagrangian measurements performed under connected flow conditionsbetween the three stationary sites were used to estimate the influence ofthe Paris emission plume onto its surroundings, which was found to be rathersmall. Rough estimates for the impact of the Paris emission plume on thesuburban areas can be inferred from these measurements: Volume mixing ratiosof 1–14 ppb of NOx, and upper limits for mass concentrations ofabout 1.5 μg m−3 of black carbon and of about 3 μg m−3 of hydrocarbon-like organic aerosol can be deduced whichoriginate from both, local emissions and the overall Paris emission plume.The secondary aerosol particle phase species were found to be notsignificantly influenced by the Paris megacity, indicating their regionalorigin. The submicron aerosol mass concentrations of particulate sulphate,nitrate, and ammonium measured during time periods when air masses wereadvected from eastern central Europe were found to be similar to what hasbeen found from other measurement campaigns in Paris and south-centralFrance for this type of air mass origin, indicating that the resultspresented here are also more generally valid.

    来源:Atmospheric Measurement Techniques

    作者:S. Yilmaz;F. Wittrock;T. Wagner;等

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    No abstract available.

      来源:Atmospheric Measurement Techniques

      作者:A. Wahner;D. S. Venables;R. Varma;等

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      The detection of atmospheric NO3radicals is stillchallenging owing to its low mixing ratios (≈ 1 to300 pptv) in the troposphere. While long-path differentialoptical absorption spectroscopy (DOAS) has been a well-establishedNO3detection approach for over 25 yr, newly sensitivetechniques have been developed in the past decade. This publicationoutlines the results of the first comprehensive intercomparison ofseven instruments developed for the spectroscopic detection oftropospheric NO3.Four instruments were based on cavityring-down spectroscopy (CRDS), two utilised open-path cavity-enhancedabsorption spectroscopy (CEAS), and one applied "classical"long-path DOAS.The intercomparison campaign "NO3Comp" was held atthe atmosphere simulation chamber SAPHIR in Jülich (Germany) in June2007. Twelve experiments were performed in the well-mixed chamber forvariable concentrations of NO3, N2O5, NO2,hydrocarbons, and water vapour, in the absence and in the presence ofinorganic or organic aerosol.The overall precision of the cavityinstruments varied between 0.5 and 5 pptv for integrationtimes of 1 s to 5 min; that of the DOAS instrument was9 pptv for an acquisition time of 1 min.TheNO3data of all instruments correlated excellently with theNOAA-CRDS instrument, which was selected as the common referencebecause of its superb sensitivity, high time resolution, and mostcomprehensive data coverage.The median of the coefficient ofdetermination (r2) over all experiments of the campaign(60 correlations) is r2 = 0.981(quartile 1 (Q1): 0.949; quartile 3 (Q3): 0.994; min/max: 0.540/0.999).Thelinear regression analysis of the campaign data set yielded very smallintercepts (median: 1.1 pptv; Q1/Q3: −1.1/2.6 pptv;min/max: −14.1/28.0 pptv), and the slopes of theregression lines were close to unity (median: 1.01; Q1/Q3: 0.92/1.10;min/max: 0.72/1.36).The deviation of individual regression slopes fromunity was always within the combined accuracies of each instrumentpair.The very good correspondence between the NO3measurements by all instruments for aerosol-free experiments indicatesthat the losses of NO3in the inlet of the instruments weredetermined reliably by the participants for the correspondingconditions.In the presence of inorganic or organic aerosol, however,differences in the measured NO3mixing ratios were detectableamong the instruments.In individual experiments the discrepanciesincreased with time, pointing to additional NO3 radicallosses by aerosol deposited onto the filters or on the inlet walls of theinstruments. Instruments using DOAS analyses showed no significanteffect of aerosol on the detection of NO3. No hint of a crossinterference of NO2 was found. The effect of non-Lambert–Beerbehaviour of water vapour absorption lines on the accuracy of theNO3 detection by broadband techniques was small and wellcontrolled.The NO3Comp campaign demonstrated the high quality,reliability and robustness of performance of current state-of-the-artinstrumentation for NO3 detection.

        来源:Atmospheric Measurement Techniques

        作者:J. T. Jayne;D. R. Worsnop;U. Rohner;等

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        We present a new instrument for monitoring aerosol composition, thetime-of-flight aerosol chemical speciation monitor(ToF-ACSM), combining precision state-of-the-arttime-of-flight mass spectrometry with stability, reliability, andeasy handling, which are necessities for long-term monitoringoperations on the scale of months to years. Based on Aerodyneaerosol mass spectrometer (AMS) technology, the ToF-ACSM providescontinuous online measurements of chemical composition and mass ofnon-refractory submicron aerosol particles. In contrast to thelarger AMS, the compact-sized and lower-priced ToF-ACSM does notfeature particle sizing, similar to the widely-used quadrupole-ACSM(Q-ACSM). Compared to the Q-ACSM, the ToF-ACSM features a bettermass resolution of M/ΔM = 600 and better detectionlimits on the order of −3 for a timeresolution of 30 min. With simple upgrades these limits can bebrought down by another factor of ~ 8. This allows foroperation at higher time resolutions and in low concentrationenvironments. The associated software packages (single packages forintegrated operation and calibration and analysis) provide a highdegree of automation and remote access, minimising the need fortrained personnel on site. Intercomparisons with Q-ACSM, C-ToF-AMS,nephelometer and scanning mobility particle sizer (SMPS)measurements, performed during a first long-term deployment (> 10months) on the Jungfraujoch mountain ridge (3580 m a.s.l.) in theSwiss Alps, agree quantitatively. Additionally, the mass resolutionof the ToF-ACSM is sufficient for basic mass defect resolved peakfitting of the recorded spectra, providing a data stream notaccessible to the Q-ACSM. This allows for quantification of certainhydrocarbon and oxygenated fragments (e.g. C3H7+ andC2H3O+, both occurring at m/Q = 43 Th), as well asimproving inorganic/organic separation.

          来源:Atmospheric Measurement Techniques

          作者:J.-J. Morcrette;J. W. Kaiser;A. Benedetti;等

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          A new fast clear-sky model called McClear was developed to estimate thedownwelling shortwave direct and global irradiances received at ground levelunder clear skies. It is a fully physical model replacing empiricalrelations or simpler models used before. It exploits the recent results onaerosol properties, and total column content in water vapour and ozoneproduced by the MACC project (Monitoring Atmosphere Composition andClimate). It accurately reproduces the irradiance computed by the libRadtranreference radiative transfer model with a computational speed approximately105 times greater by adopting the abaci, or look-up table, approachcombined with interpolation functions. It is therefore suited forgeostationary satellite retrievals or numerical weather prediction schemeswith many pixels or grid points, respectively. McClear irradiances werecompared to 1 min measurements made in clear-sky conditions at severalstations within the Baseline Surface Radiation Network in various climates.The bias for global irradiance comprises between −6 and25 W m−2. The RMSE ranges from 20 W m−2 (3% of the meanobserved irradiance) to 36 W m−2 (5%) and the correlationcoefficient ranges between 0.95 and 0.99. The bias for the direct irradiancecomprises between −48 and +33 W m−2. The root mean square error (RMSE) ranges from33 W m−2 (5%) to 64 W m−2 (10%). The correlationcoefficient ranges between 0.84 and 0.98. This work demonstrates the qualityof the McClear model combined with MACC products, and indirectly the qualityof the aerosol properties modelled by the MACC reanalysis.

            来源:Atmospheric Measurement Techniques

            作者:J. T. Jayne;D. R. Worsnop;U. Rohner;等

            使用许可:署名(BY)

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