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Measurement campaigns

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Aircraft and airport emissions

To study the impact of emissions at an airport on local air quality, a measurement campaign the Zurich airport was performed from June 30 to July 15, 2004 (Schürmann et al., 2007). CO concentrations in the vicinity of the terminals were found to be highly dependent on aircraft movement, whereas NO concentrations were dominated by emissions from ground support vehicles. The measured emission indices for aircraft showed a strong dependence upon engine type (Schäfer et al., 2000; Schäfer et al., 2003). Among the VOC, reactive C2-C3 alkenes were found in significant amounts in the exhaust of an engine compared to ambient levels. The benzene to toluene ratio was used to discriminate exhaust from refuelling emission. In refuelling emissions, a ratio well below 1 was found, while for exhaust this ratio was usually about 1.7.

 

 
Schematic picture of the experimental setup at Zurich airport.

 

 

 

NO (μg m-3)

NO2 (μg m-3)

CO (mg m-3)

 

Min

Median

Max

Min

Median

Max

Min

Median

Max

Pier A

Bdl

3.1

61.1

3.6

19.6

103.8

-

-

-

Pier B

Bdl

6.6

76.3

3.0

17.5

98.3

-

-

-

Taxiway

0.07

15.4

132.0

0.04

22.6

274.0

0.06

0.19

4.49

Handling

0.8

25.2

636.0

0.3

29.6

131.0

0.00

0.22

1.91

Bdl: below detection limit of 2 μg m-3 for NO2, 4 μg m-3 for NO and 6 µg m-3 for CO
Measurement statistics for the entire field experiment (June 30 – July 15, 2004): For pier A and B, half hourly means of NOx in situ measurements are shown. For the other two sites FTIR short term data of 3 minutes resolution are reported. For CO, only daytime measurements were available. 

 

 

To develop a database of real-world emission source strengths as well as air quality and meteorological data a measurement campaign was carried out at the Athens International Airport (AIA) in frame of the Network of Excellence ECATS. The campaign from 13 until 25 September 2007 was realised with the aid of existing monitoring equipment at the AIA as well as instrumentation from the participant partners (National and Kapodistrian University of Athens, Bergische Universität Wuppertal and FZK) that was transferred to the AIA, allowing the sharing of knowledge and infrastructure (Schäfer et al., 2008b). The influence of airport emissions upon air quality in the surroundings was important. Other sources can be more important as e.g. in the morning the road traffic peak. The estimation of the airport emission source strengths were detected due to different wind directions and the determination of mixing layer height. The influence of aircraft emissions upon airport air quality were studied (NO2, NO, CO, VOC, PM) by taking into account the chemistry.

 

 

NO2 concentrations measured by DOAS and departing aircraft at the runway nearby site A on 15 September 2007.

 

Boundary layer structure and air quality

Upper Inn valley

Simultaneous surface-based remote sensing with optical (ceilometer) and acustical (SODAR) methods was applied to infer the diurnal variation of the structure of the atmospheric boundary-layer with high temporal resolution. Automatic mixing layer height monitoring was performed by continuous SODAR and ceilometer measurements in the Inn valley near Innsbruck, Austria during the winter measuring campaign 2005/2006 on air and noise pollution of the project ALPNAP (Schäfer et al., 2008). In clear and cold winter nights sometimes several layers could be detected with both instruments. Ceilometer and SODAR partly complement each other. The variation of air pollutant concentrations near the motorway was determined on the basis of path-averaged (DOAS) and in situ measurements. During several periods the air pollutants accumulated from day to day and frequent exceedances of NO2 and PM10 thresholds were detected. Analysis confirms that the typical weather phenomena associated with stable high-pressure regimes are the main factor for the observed pollution burden. Analysis reveals that this is a consequence of vertical mixing due to the influence of mountain specific wind systems, like thermally driven and quasi-periodic valley or slope winds. Compared to previous investigations an increased NO2/NOx ratio was observed during the measurement campaign which is related to enhanced NO2 emissions from road traffic in consequence to fleet composition and emission changes.

 

 

Daily mean values of MLH above ground level (agl) from SODAR measurements at the site 2 during the campaign in January 2006. Two high pressure periods are visible lasting from 06 until 15 January and from 24 January until 4 Feb 2006, shortly intermitted on 26/27 January 2006.

 

 

CO (dotted curve, right scale), NOx (dashed-dotted-dotted curve, right scale), PM10 (dashed curve, left scale) concentrations and temperature (solid curve, left scale) as daily means over 29 days (03 January 2006 to 31 January 2006) from measurements near Schwaz.

 

 

Hannover and Munich

During continuous measurements in Hanover, Germany, from 2001 until 2003 (Schatzmann et al., 2006; Schäfer et al., 2005) and around Munich, Germany, in summer and winter 2003 mixing layer heights were determined by SODAR, ceilometer and RASS (Schäfer et al., 2008; Wiegner et al., 2006). The temporal variations of the concentrations of PM10 and PM2.5 as well as of CO and NOx simultaneously measured near the surface were investigated and correlated with the mixing layer height derived from SODAR data (Schäfer et al., 2006). The analyses show that the correlations of pollutant concentrations with MLH are smallest inside street canyons. Correlations at the urban background stations are larger in winter than in summer, and they are larger for the urban stations than for the rural stations. It turns out further that the correlation of NOx concentrations with MLH is larger than the correlation of particles concentrations.

 

 
Seasonal variation of the square of the correlation coefficient R2 and parameters of exponential relationship for NOx concentration with mixing layer height (MLH) from SODAR for the roof-top station at the street canyon Göttinger Strasse in Hanover (urban background) during all seasons.

 

Relations of the aerosol optical depth with aerosol mass concentration near the ground, particulate matter, has been studied on the basis of measurements (Schäfer et al., 2002; Alföldy et al., 2007; Schäfer et al., 2008). It is implied that the aerosol optical depth is caused mainly by attenuation processes within the mixing layer because this layer includes nearly all atmospheric aerosols. Thus the mixing layer height is required together with the aerosol optical depth, measured by ground-based sun-photometers (around 560 nm), to get information about aerosols near the ground. Investigations were performed during two measurement campaigns in and near Munich in May and November/December 2003 on the basis of daily mean values. Using the aerosol optical depth and mixing layer height measurements by SODAR the aerosol extinction coefficient of the mixing layer has been calculated. The correlation of this quantity with the measured PM10, PM2.5 and PM1 mass concentrations near the ground by performing a linear regression and thus providing a mass extinction efficiency gives squares of the correlation coefficients (R2) between 0.48 (PM1 during summer campaign) and 0.90 (PM2.5 during winter campaign).

 

 
Scatter plot of ambient PM mass concentrations (in µg/m3) with aerosol extinction coefficients (in km-1) during the winter measurement campaign. A linear regression was performed (slope in m2/mg) through zero and squares of correlation coefficient (R2) are given. Mixing layer height was measured by a SODAR in Maisach only. AOD of spectral range close to 560 nm and PM mass concentration were measured in Maisach and in Munich.

 

Augsburg

Two ceilometers and a SODAR were operated in the centre and the outskirts of the city of Augsburg beginning in September 2006. The operation of the CL31 was from 20 September 2006 within the city center (Augsburg FH). The LD40 operation period started on 20 December 2006 together with in situ concentration measurements of CO, NO, NOx, and O3 inside a van as well as PM10 at the northern edge of the city (Augsburg BIfA). Both ceilometers were running at the same location during the inter-comparison campaign from 08 May 2007 until 05 June 2007 nearby the SODAR (Augsburg LfU). The main parameters of these instruments are:

  • LD40: wavelength: 855 nm, height resolution: 7.5 m, double lens, range: 13,000 m,
  • CL31: wavelength: 905 nm, height resolution: 10 m, one lens, range: 7,500 m.

During rain and fog a determination of MLH was not possible. It was concluded that remote sensing devices like ceilometer and SODAR are well suited to observe several meteorological parameters and their vertical distribution which are of relevance for air quality (aerosol concentrations and dispersion parameters). The combined operation of acoustic and optical remote sensing techniques offers the possibility to analyse the vertical structure of the atmospheric boundary layer. Both ceilometers agree well with the SODAR measurement results. In order to have more accurate results for the investigation of MLH at different sites, instruments with same technical properties should be employed.

Reference: Schäfer, K., Emeis, S., Jahn, C., Münkel, C., Münsterer, C., Im, U.: Long-term monitoring of layering of lower atmosphere in urban environment by ceilometer. In: Remote Sensing of Clouds and the Atmosphere XII, Adolfo T. Comeron, Klaus Schäfer, James R. Slusser, Richard H. Picard (eds.), Proceedings of SPIE, Bellingham, WA, USA, Vol. 6745 (2007), 6745OW-1 – 6745OW-12; Remote Sensing, SPIE Europe Remote Sensing, 17.–21. September 2007, Florence, Italy.

 

 
MLH retrievals from ceilometers LD40 and CL31 backscatter data measurements at the northern edge of the city and at the city centre (right) on 16 Februar 2007 (minimum temperature -3°C, maximum temperature 8°C, average humidity 79 %, average wind speed 3 m/s, maximum wind speed 24 km/h, wind direction E (SE – SW), fog in early morning, mostly clear afterwards).

 

 

Comparison of MLH retrievals from ceilometers LD40 and CL31 backscatter data measurements on 16 February 2007.

 

 

Improvement of non-intrusive measurement methods – inverse dispersion modelling

Emission rates of important diffuse sources like gas stations are spatial non-homogeneous so that the inverse dispersion modelling was improved to obtain emission rates by non-intrusive open-path spectroscopic measurements (FTIR and DOAS) in the exhaust plume and simultaneous meteorological measurements (Friedrich et al., 2002). The area emission rates of important VOCs from gasoline filling processes as precursors of photo-oxidants were determined during some campaigns. Several gas stations and tank farms were investigated and compared to evaluate the currently available emission factors for gasoline stations and to examine the efficiency of their gasoline vapour recovery system. Further, the benzene emission rates of tankers during ventilation and alternative use of gas balancing were determined.

 

 
Benzene concentrations at a DOAS path nearby a gasoline filling station in ppb, wind speeds and wind directions as well as the calculated emission rates by inversion of the dispersion model MISKAM (2 hours mean) in 1 µg/(m2s) corresponding to an emission of 300 mg/s from the emitting area of 300 m2.

 

Up-scaling of greenhouse gas fluxes between the soil and the atmosphere

To the emissions of N2O from a shallow sandy aquifer and a measurement campaign was performed within the frame of a DFG funded project “N2O emission measurements at a scale of 100 m” from March 2006 until June 2008. The dynamics of the greenhouse gas fluxes between the soil and the atmosphere was investigated in the “Fuhrberger Feld” catchment in northern Germany. An important objective of this research was to quantify spatially heterogeneous emissions of N2O from the soil into the atmosphere at the field scale. The basic idea of the measurement concept was the comparison of measurements of N2O emissions at the field scale compared to point measurements of N2O fluxes by applying the closed chamber method for very small-scale investigations at an area of about 0.05 m2 and a measuring tunnel with a path-averaging concentration measurement method (open-path FTIR) for integration over an area of about 500 m2 (spatial scaling factor 104). The leakage rate of the measuring tunnel was studied also (Schäfer et al, 2008d). The chamber measurements show a high spatial variation of the emissions from soil.

Reference: Schäfer, K., Emeis, S., Jahn, C., Wiwiorra, M.: Emissionsmessungen von N2O an der Bodenoberfläche auf einer Skala von 100 m. In: VDI-Berichte „Neue Entwicklungen bei der Messung und Beurteilung der Luftqualität“, VDI-Verlag GmbH, Düsseldorf 2040, (2008d), 277-280 (ISBN 978-3-18-092040-5); Tagung „Neue Entwicklungen bei der Messung und Beurteilung der Luftqualität“, 24.-25.06.2008 in Nürnberg, Poster.

 

 

The Figure (right lower part) with the measuring tunnel and the study site where the closed chamber measurements are located in the Fuhrberger Feld aquifer shown in the groundwater flowline strip of 11 km2. The North direction is indicated. The lower part of the Figure shows the configuration of the measuring tunnel.

 

 

 
Concentration increase in the measuring tunnel air during 6 hours for N2O in ppb on 20 and 21 June 2006. The closing of the plastic cover started with the measurements and it was closed totally at 20 June 2006, 18:45 CET and at 21 June 2006, 19:41 CET.

 

 

Contact: Klaus Schäfer, Stefan Emeis, Carsten Jahn