Project leader and team Christoph Zellweger, Martin Steinbacher, Martin K. Vollmer, Christoph Hüglin (project leader)

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1 Activity Report 6 Name of research institute or organization: EMPA Materials Science and Technology Title of project: National Air Pollution Monitoring Network (NABEL) Project leader and team Christoph Zellweger, Martin Steinbacher, Martin K. Vollmer, Christoph Hüglin (project leader) Project description: The national air pollution monitoring network NABEL is a joint project of the Swiss Federal Office for the Environment (BAFU/FOEN) and Empa. The NABEL network consists of 16 monitoring stations that are distributed all over Switzerland. The monitoring stations represent the most important air pollution levels. The NABEL site at Jungfraujoch is a very low polluted site, representing a background station for the lower free troposphere in central Europe. The measurement programme at Jungfraujoch includes continuous in-situ analyses of ozone (O 3 ), carbon monoxide (CO), nitrogen monoxide (NO), nitrogen dioxide (NO 2 ), the sum of nitrogen oxides (NO y ) and sulfur dioxide (SO 2 ). In addition, an extended set of halocarbons and a selection of VOCs (alkanes, aromatics) are measured with a time resolution of four hours. Daily samples are taken for determination of gaseous SO 2 and for particulate sulphur. The concentrations of total suspended particles are continuously observed as well as measured as 24-hour bulk samples. Intercomparisons of different techniques measuring the same species are a valuable tool to evaluate the performance of the respective measurement methods. For permanent in-situ observations of CO at the Jungfraujoch three measurement techniques (non-dispersive infrared analyzers (NDIR), gas chromatography with HgO reduction detector (GC/HgO), gas chromatography with flame ionization detector (GC/FID) are currently in use. Additionally, a fourth instrument (a vacuum ultraviolet resonance fluorescence (VURF) analyzer) operated by the World Calibration Centre (WCC) for Surface Ozone, Carbon Monoxide and Methane was running at Jungfraujoch from 11 January 6 to 16 March and from 26 July to 19 September 6. Figure 1 gives an overview of the available time series of 10-minute averages (VURF, NDIR) and single analysis every 30 minutes (GC systems) during the winter campaign. The difference of the NDIR and GC instruments to the VURF analyzer is presented in Figure 2, and a scatter plot matrix is shown in Figure 3. Figures 1 and 2 show a good general agreement among the instruments. However, a small temporal drift was observed for the NDIR instrument. This is most likely due to the applied zero correction based on monthly averages of the automatic zero check every second day. This indicates that zero drift and signal noise are the limiting factors for accurate CO measurements with NDIR instruments. 27

2 Activity Report 6 CO [ppb] VURF NDIR GC/FID GC/HgO 01/12 01/22 02/01 02/11 02/21 03/03 03/13 Date (mm/dd) Figure 1: Simultaneous measurements of carbon monoxide (CO) at the Jungfraujoch with four different measurement techniques. All instruments were calibrated using their own calibration standard. The standards used for the GC systems were calibrated on the VURF instrument; the standard of the VURF instrument was calibrated against the WMO-0 calibration scale (Novelli et al., 3). The NDIR instrument used a NIST traceable calibration gas. Laboratory experiments showed excellent agreement between NIST and WMO-0 calibration scales. Therefore differences should not arise from scale issues. The remaining differences can be explained as follows: Continuous vs. discrete techniques Calibration issues, e.g. zero correction of NDIR analyzers and non-linearity correction of GC/HgO instruments References Novelli P. C., Masarie K. A., Lang P. M., Hall B. D., Myers R., Elkins J. W., 3. Reanalysis of tropospheric CO trends: Effects of the wildfires. Journal of Geophysical Research 108, 4464, doi: 1029./2JD

3 GC/HgO - VURF [ppb] GC/FID - VURF [ppb] NDIR - VURF [ppb] 20 International Foundation HFSJG Activity Report Day Figure 2: Box plots of the daily differences to the VURF instrument. 10-min averages (VURF, NDIR) and single injections (every 30 min, GC/FID and GC/HgO) were used. VURF NDIR GC/FID GC/HgO Figure 3: Scatter plot matrix of the carbon monoxide intercomparison at Jungfraujoch. 10-min averages were used for the continuous techniques, and single injection within these 10 minutes for the GC systems. 29

4 Activity Report 6 Key words: Air pollution, long-term measurements, carbon monoxide, intercomparison Internet data bases: Collaborating partners/networks: Bundesamt für Umwelt (BAFU)/ Federal Office for the Environment (FOEN) Global Atmosphere Watch (GAW) Labor für Atmosphärenchemie, Paul Scherrer Institut Meteo Schweiz Scientific publications and public outreach 6: Refereed journal articles Walker, S. J., Evans M. J., Jackson A. V., Steinbacher M., Zellweger C., McQuaid J. B., 6. Processes controlling the concentration of hydroperoxides at Jungfraujoch Observatory, Switzerland. Atmospheric Chemistry and Physics 6, Zanis P., Ganser A., Zellweger C., Henne S., Steinbacher M., Staehelin J., 6. Seasonal variability of measured Ozone Production Efficiencies in the lower free troposphere of Central Europe. Atmospheric Chemistry and Physics Discussions 6, Conference contributions Folini D., Ubl S. Kaufmann P., Reimann S. - Lagrangian Particle Dispersion Modeling at Jungfraujoch, CHIOTTO final workshop, Amsterdam, Netherlands, March 09 10, 6. Steinbacher M., Vollmer M. K., Reimann S. - Radiative forcing budget of non-co 2 trace gases at the high-alpine site Jungfraujoch, Switzerland; Joint CACGP/IGAC/WMO symposium 'Atmospheric Chemistry at the Interfaces'; Cape Town, South Africa, September 17 22, 6. Steinbacher M., Schwarzenbach B, Buchmann B, Hueglin C. - Continuous in-situ air quality measurements at the Jungfraujoch as part of the Swiss National Air Pollution Monitoring Network (NABEL); Conference 'Research at Jungfraujoch'; Interlaken, September 11 14, 6. Steinbacher M., Vollmer M. K., Reimann S. - Radiative forcing budget of non-co 2 trace gases at the high-alpine site Jungfraujoch; Conference 'Research at Jungfraujoch'; Interlaken, September 11 14, 6. Steinbacher M., Vollmer M. K., Reimann S. - Quasi-continuous CH 4, N 2 O, and SF6 measurements at the high Alpine site Jungfraujoch: influence of transport processes and emissions estimates; GEIA 6 conference; Paris, France, November 29 December 01, 6. Zellweger C., Buchmann B., Klausen J., Steinbacher M., Vollmer M. K. - Carbon monoxide measurements with four techniques at the high-alpine GAW site Jungfraujoch, Switzerland, Joint CACGP/IGAC/WMO symposium 'Atmospheric Chemistry at the Interfaces'; Cape Town, South Africa, September 17 22, 6. 30

5 Activity Report 6 Data books and reports BAFU 6: NABEL Luftbelastung 5. Umwelt-Zustand Nr Bundesamt für Umwelt, Bern. 134 S. Address: EMPA Laboratory for Air Pollution/Environmental Technology Ueberlandstrasse 129 CH-8600 Dübendorf Contacts Martin Steinbacher Tel.: Fax: martin.steinbacher@empa.ch URL: 31

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