Fraunhofer-Institut für Atmosphärische Umweltforschung IFU

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  • Publication
    Airborne measurements of nucleation mode particles I: Coastal nucleation and growth rates
    ( 2007)
    O'Dowd, C.D.
    ;
    Yoon, Y.J.
    ;
    Junkerman, W.
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    Aalto, P.
    ;
    Kulmala, M.
    ;
    Lihavainen, H.
    ;
    Viisanen, Y.
    A light aircraft was equipped with a bank of Condensation Particle Counters (CPCs) (50% cut from 3-5.4-9.6 nm) and a nano-Scanning Mobility Particle Sizer (nSMPS) and deployed along the west coast of Ireland, in the vicinity of Mace Head. The objective of the exercise was to provide high resolution micro-physical measurements of the coastal nucleation mode in order to map the spatial extent of new particle production regions and to evaluate the evolution, and associated growth rates of the coastal nucleationmode aerosol plume. Results indicate that coastal new particle production is occurring over most areas along the landsea interface with peak concentrations at the coastal plume-head in excess of 106 cm-3. Pseudo-Lagrangian studies of the coastal plume evolution illustrated significant growth of new particles to sizes in excess of 8 nm approximately 10 km downwind of the source region. Close to the plume head (<1km) growth rates can be as high as 123-171 nm h-1, de creasing gradually to 53-72 nm h-1 at 3km. Further along the plume, at distances up to 10km, the growth rates are calculated to be 17-32 nm h-1. Growth rates of this magnitude suggest that after a couple of hours, coastal nucleation mode particles can reach significant sizes where they can contribution to the regional aerosol loading.
  • Publication
    Multipass open-path Fourier-transform infrared measurements for nonintrusive monitoring of gas turbine exhaust composition
    ( 2005)
    Schafer, K.
    ;
    Brockmann, K.
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    Heland, J.
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    Wiesen, P.
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    Jahn, C.
    ;
    Legras, O.
    The detection limits for NO and NO2 in turbine exhausts by nonintrusive monitoring have to be improved. Multipass mode Fourier-transform infrared (FTIR) absorption spectrometry and use of a White mirror system were found from a sensitivity study with spectra simulations in the mid-infrared to be essential for the retrieval of NO2 abundances. A new White mirror system with a parallel infrared beam was developed and tested successfully with a commercial FTIR spectrometer in different turbine test beds. The minimum detection limits for a typical turbine plume of 50 cm in diameter are approximately 6 parts per million (ppm) for NO and 9 ppm for NO2 (as well 100 ppm for CO2 and 4 ppm for CO).
  • Publication
    Metabolism of reduced and inorganic sulphur in pea cotyledons and distribution into developing seedlings
    ( 2002)
    Herschbach, C.
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    Pilch, B.
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    Tausz, M.
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    Rennenberg, H.
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    Grill, D.
    Sulphur export and redistribution from the cotyledons of pea (Pisum sativum) seedlings was investigated to determine the role of cotyledons as a sulphur source during root-shoot axis development. Thiols and sulphate were analysed using standard biochemical techniques, and S-35 fed to cotyledons by injection. After S-35-cysteine injection, c. 50% of the labelled S in the cotyledon was metabolized to S-35-sulphate. This reaction was partly inhibited by aminooxyacetic acid, an inhibitor of cysteine-desulfhydrase. After S-35-sulphate application, c. 1% of the radiolabel was found in cysteine and glutathione in the cotyledon. After 2 h, c. 20% of the S-35 was transported into the root-shoot axis independently of whether S-35-sulphate or S-35-cysteine was injected into the cotyledon. After 4 h, 40% of S-35 was found outside the cotyledon. Cotyledons of pea seedlings are capable of sulphate assimilation and cysteine degradation. Both sulphate and reduced sulphur were allocated from the cotyledons to the developing tissues of the pea seedlings.
  • Publication
    Tuning characteristics of InAsSb continuous-wave lasers
    ( 2002)
    Sherstnev, V.
    ;
    Krier, A.
    ;
    Popov, A.
    ;
    Werle, P.
    We present a detailed analysis of the tuning characteristics of InAsSb continuous-wave (cw) single-frequency lasers emitting at 3.3 µm (3050 cm-1). The lasers demonstrate a tuning range of -7.5 cm-1 by changing the current and -3.5 cm-1 by changing the heat sink temperature without mode hopping. The tuning rates are of -0.015 to -0.089 cm-1/mA and -0.11 to 0.27 cm-1/K. The laser tunes to the blue side both with increasing injection current and heat sink temperature. The extended tuning is attributed to the carrier heating effect in the cw operation and the band-filling effect in the presence of strong losses.
  • Publication
    Determination of anthropogenic emission ratios in the Augsburg area from concentration ratios results from long-term measurements
    ( 2002)
    Klemp, D.
    ;
    Mannschreck, K.
    ;
    Patz, H.W.
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    Habram, M.
    ;
    Matuska, P.
    ;
    Slemr, F.
  • Publication
    Statistical study of the diurnal variation of modeled and measured NMHC contributions
    ( 2002)
    Möllmann-Coers, M.
    ;
    Klemp, D.
    ;
    Mannschreck, K.
    ;
    Slemr, F.
    The aim of the EVA project is to investigate the precision of modeled emission inventories for a city based on experimental data from two field campaigns in March and October 1998 (Slemr et al., J. Atmos. Chem., 2001). According to the results of the emission inventory model (Kühlwein et al., Atmos. Environ., this issue) for the campaigns, the measured nonmethane hydrocarbons (NMHCs) should originate predominantly from evaporation processes. In this paper these model results are discussed from a meteorological point of view. The results from atmospheric dispersion calculations with a Gaussian plume model are compared with measurements of NMHCs and CO at a site few kilometers downwind of the city of Augsburg. The dispersion model results point out that the correlations of the individual NMHCs against CO lead to different qualities of correlation for NMHCs co-emitted with CO (i.e. from combustion processes) and NMHCs which are not co-emitted with CO (i.e. from evaporation processes). However, using the correlation coefficients r2, as a measure of the quality of the correlation, the correlations of several NMHCs for which strong evaporation emissions are predicted from the emission inventory model do not show remarkable differences in the r2 when compared with the correlations for species predominantly emitted from combustion processes. Thus, the NMHC emissions are found to be dominated by emissions from combustion processes and the influence of evaporation processes on anthropogenic NMHC emissions seems to be considerably overestimated by the emission model. This is in agreement with the results of Mannschreck et al. (Atmos. Environ., 2001) which are based on the NMHC composition of the Augsburg city plume.
  • Publication
    Highlights of the tropospheric lidar studies at IFU within the TOR project
    ( 2002)
    Carnuth, W.
    ;
    Kempfer, U.
    ;
    Trickl, T.
    A summary of the ozone soundings with the tropospheric ozone lidar at IFU in the years 1991 and 1993 is given. The results cover vertical distributions obtained under a variety of meteorological conditions in different seasons such as during high pressure, before and after frontal passages and during stratospheric air intrusions. The lidar time series, carried out between typically 0.25 and 10 km and at intervals of about 1 h, are an excellent tool for transport studies. Quite frequently contributions of different processes may be observed even simultaneously which may yield insight on the troposphere as a whole. Although the time series were limited to single days during that phase information on a number of relevant transport processes could be extracted. In particular, the uplifting in the Alpine thermal wind system was investigated. The air in the valley is vented to heights in part even beyond 4 km a.s.l. during fair-weather summer days. The high efficiency of the underlying mechanism suggests a major contribution of the orographically induced transport in the Alps to the pollution export from the Central European boundary layer. A spectacular case of trans-Alpine ozone transport was examined which resulted in an ozone increase by about 40% after sunset. This case may, again, reflect the role of the Alps in the redistribution of air pollution in a larger area. In addition, episodes of long-range ozone and aerosol transport have been studied. In this paper, we present the example of intense Fohn with advection of dust-loaded air from the Sahara desert and beyond containing just 35 ppb of O-3. A rather complex layering may be observed after cold-front passages associated with subsequent anticyclonic advection. The analysis of a two-day vertical-sounding series reveals that the air in different height ranges originated in the troposphere or stratosphere above rather different source regions, even in the lowermost 4 km above the United States. More recent studies have confirmed the reproducibility of the general layer pattern under such conditions. The in part considerable difference in ozone concentration makes the definition of a free-tropospheric background ozone level a difficult task.
  • Publication
    Evaluation of an emission inventory by comparisons of modelled and measured emission ratios of individual HCs, CO and NOx
    ( 2002)
    Mannschreck, K.
    ;
    Klemp, D.
    ;
    Kley, D.
    ;
    Friedrich, R.
    ;
    Kühlwein, J.
    ;
    Wickert, B.
    ;
    Matuska, P.
    ;
    Habram, M.
    ;
    Slemr, F.
    Air quality models require emission inventories of individual compounds with high temporal and spatial resolution. These emission inventories are calculated by complex emission models. To evaluate these models, emission ratios of non-methane hydrocarbons (HCs, containing only H- and C-atoms), CO and NOx of the city of Augsburg were determined during two field campaigns in March and October 1998. The measured emission ratios have been compared with emission ratios calculated by an emission model at two accuracy levels. Only C-2-C-10 HCs were measured quantitatively by the applied techniques. C-11-C-13 HCs were measured with losses increasing with the number of C atoms, oxygenated and halogenated volatile organic compounds were not measured at all. The direct comparison could be made only for those HCs whose individual emissions can be specified by the model. They represent 21% of the total predicted volatile organic compound emissions and-according to the model-originate to a large percentage from traffic-related emission. The measured HCi/HCsum emission ratios (HCsum:=Sigma(HCi) for C-2-C-10-HCs and HCi:=mixing ratio of an individual hydrocarbon) for these compounds agreed within 30% for most compounds. The HCi/HCsum emission ratios measured in Augsburg are very similar to emission ratios from traffic-related sources suggesting that the emission model reflects the traffic emissions quite well. In order to consider all measured HCs for comparison the share of unspecified HCs, which are detectable by the GC system and should therefore be included in the experimental results, was estimated. Taking this into account yields a deviation between modelled and measured monthly mean values of HCi/CO and HCi/NOx of about 40%. The comparison of modelled and measured HCi/CO with HCi/HCsum emission ratios derived from the investigation based on single events confirms this finding: in this case an overestimation by the model of a factor of 1.5-2 was found. Since modelled and measured NOx and CO emissions agreed well within the uncertainty ranges, these deviations can be attributed to overestimation of HC emissions. Unspecified HC emissions mainly originate from solvent mixtures thus the overestimation of their emissions could explain the observed deviations. Regarding one specific HC which originates nearly exclusively from solvent emissions, i.e. n-decane, yields an overestimation of about a factor of 10 by the model.
  • Publication
    Exchange of trace gases between soils and the atmosphere in Scots pine forest ecosystems of the northeastern German lowlands
    ( 2002)
    Butterbach-Bahl, K.
    ;
    Breuer, L.
    ;
    Gasche, R.
    ;
    Willibald, G.
    ;
    Papen, H.
  • Publication
    Emissions of the city of Augsburg determined using the mass balance method
    ( 2002)
    Kalthoff, N.
    ;
    Corsmeier, U.
    ;
    Schmidt, K.
    ;
    Kottmeier, C.
    ;
    Fiedler, F.
    ;
    Habram, M.
    ;
    Slemr, F.
    Air quality models require emission data of air pollutants with high temporal and spatial resolution. The highly resolved emissions are calculated by complex emission models and may thus be subject to considerable uncertainties. To assess the uncertainty of the emission model calculations, emissions of the city of Augsburg in southern Germany were determined experimentally on several days in October 1998 using the technique of mass balance. Two algorithms were used to estimate the CO and NOx emissions from the data measured by two research aircraft, two tethered balloons, and an airship on the lateral surface enclosing the area of investigation. The two algorithms provided results which agree within the calculated uncertainties. The differences can be attributed mainly to the different interpolation methods applied to the layer between the lowest flight level and the ground. The measurements show that on the different weekdays both CO and NOx emissions varied by about a factor of two which is much larger than the variability predicted by the emission model. Higher than predicted CO emissions were observed on Saturday, 10 October 1998, whereas NOx emissions on 10 October were substantially smaller than predicted by the emission model.