High-precision MIR trace gas analysis for environmental applications

Transcription

1 First MIRIFISENS Workshop, Zürich, High-precision MIR trace gas analysis for environmental applications Lukas Emmenegger Air Pollution / Environmental Technology Laboratory Lukas Emmenegger@Empa.ch ; 1 Zürich, view from Uetliberg, h averages g/m 3 limit value PM NOx ETH Hönggerberg Lukas Emmenegger@Empa.ch ; 2 1

2 Empa, Laboratory for Air Pollution / Environmental Technology Measurement Modelling Instrumental Development National Air Pollution Monitoring Network (NABEL) Eulerian MIR Laser Spectroscopy WMO World Calibration center for O 3, CO, CO 2, CH 4 Lagrangian Gas Chromatography Lukas Emmenegger@Empa.ch ; 3 The European Environmental Agency (EEA) lists 8406 monitoring stations in Europe (2013). Source: AirBase: public air quality database 2

3 The standard methods are not based on laser spectroscopy Compound Lukas ; 5 main relevance standard method (mainly CEN / ISO) NH 3 (ammonia) pollutant Denuder O 3 (ozone) pollutant UV abs CH 4 (methane) GHG GC-FID N 2 O(nitrousoxide) GHG GC-ECD SO 2 (sulphur dioxide) pollutant UV Fluorescence CO (carbon monoxide) pollutant NDIR NO 2 (nitrogen dioxide) pollutant catalytic conv. NO (nitrogen monoxide) pollutant & CLD CO 2 (carbon dioxide) GHG NDIR H 2 O (water vapour) GHG Dew point * laser based at some (!) locations of the Swiss monitoring Network (NABEL) * * * * * Air pollutants / GHG absorb in the MIR Lukas Emmenegger@Empa.ch ; 6 3

4 Many different detection schemes are suitable Signal enhancement Multipass absorption cell Cavity enhanced techniques Noise reduction Wavelength/Frequency modulation Balanced detection «zero» background detection Fringe suppresion Lukas ; 7 Very simple: direct absorption spectroscopy 1 absorption laser beam sample cell detector wavenumber 1 transmission laser current Lukas Emmenegger@Empa.ch ; 8 laser wavelength wavenumber 4

5 Examples and prospects selective sensitive small CO 2 and its four stable isotopes NO 2 and NO at ppt mixing ratios reducing size and power by factor 10 direct absorption QCL spectroscopy Lukas Emmenegger@Empa.ch ; 9 selectivity CO 2 Isotopologues at Jungfraujoch Lukas Emmenegger@Empa.ch ; 10 5

6 CO 2 isotopologues natural abundance α 13 δ C α 13,s 13,ref α α 12,s 12,ref Lukas Emmenegger@Empa.ch ; 11 Simulated 3 ro-vibrational bands of CO 2 based on Hitran Abundance weighted linestrength ( cm -1 /molecule cm -2 ) O 12 C 18 O 16 O 13 C 16 O 16 O 12 C 16 O Wavenumber (cm -1 ) 2350 Lukas Emmenegger@Empa.ch ; 12 6

7 Peak Separation Resolution and Pressure Absorbance atm mbar Wavenumbers (cm -1 ) Lukas Emmenegger@Empa.ch ; 13 Spectral ratio method for CO 2 isotopologues optical path: 7 m pressure: 60 hpa scanning rate: 5 khz pulsed QCL at 4.3 m from Alpes Lasers picture: June 2007 Lukas Emmenegger@Empa.ch ; 14 7

8 Measured and Simulated Absorption Spectrum of CO Transmitance (%) spectrum fit 0.80 Linestrength [cm -1 /molecule cm -2 ] HITRAN ' s average of 5 khz spectra at 60 hpa Wavenumber (cm -1 ) Tuzson et al. Appl. Phys. B (2008) Lukas Emmenegger@Empa.ch ; 15 Precision & Stability (Allan plot) Sturm et al., ACP (2013) Lukas Emmenegger@Empa.ch ; 16 8

9 (Isotopic) variations at Jungfraujoch, 3580 masl ~10 ppm Lukas Sturm et al., AMT ; 17 (2013) Seasonal cycles of CO 2, 13 C and 18 O Mean seasonal cycles from detrended and monthly bin-averaged data (points) and the annual harmonic part of the smoothed curve fit (lines). Sturm et al., AMT (2013) Lukas Emmenegger@Empa.ch ; 18 9

10 Short-time Jungfraujoch, 3580 masl 18 O ( ) 13 C ( ) CO 2 [ppm] I II III IV IV BKG Event Tuzson et al., ACP (2011) Lukas Emmenegger@Empa.ch ; 19 Keeling plots show 13 C-CO 2 signatures of fossil fuel burning Keeling plot Tuzson et al., ACP (2011) Lukas Emmenegger@Empa.ch ; 20 10

11 sensitivity NO 2, NO, NOy measurements at Jungfraujoch Lukas ; 21 Selective measurement of NO and NO 2 at ppt mixing ratios NO 2 NO x x s average of 5 khz spectra at at 50 hpa; simulation (lower part) based on HITRAN RT cw QCL from Alpes Lasers Tuzson, AMT (2013) Lukas Emmenegger@Empa.ch ; 22 11

12 Direct measurements of NO and NO 2 by QCLAS 210 m optical path 238 reflections McManus et al., Applied Optics, 2011 Lukas Emmenegger@Empa.ch ; 23 Beware of the unexpected! NO 2 (ppb) NO 2 (ppb) :36 12:40 12: : :15 12:30 12:45 13:00 13:15 Date & Time Lukas Emmenegger@Empa.ch ; 24 12

13 Size instrumental aspects Lukas Emmenegger@Empa.ch ; 25 Toroidal Cell with cwqcl and «Fringe Killer» -> interference, fringes with absorption mask (patent pending) Lukas Emmenegger@Empa.ch ; 26 13

14 Application of the toroidal cell for CO 2 isotopes Tuzson et al., Optics Letters (2013) Lukas Emmenegger@Empa.ch ; 27 Optical setup exclusively based on QC technology Lukas Emmenegger@Empa.ch ; 28 14

15 Future multi-component MIR ambient air monitors?! Lukas ; 29 Acknowledgements Empa Béla Tuzson Markus Mangold Jana Jágerska Rolf Brönnimann Aerodyne Mark Zahniser David Nelson Barry McManus ETHZ Jérôme Faist Yargo Bonetti Pierre Joye Alpes Lasers Stephane Blaser Antoine Müller and many others Swiss National Science Foundation, nanotera.ch International Foundation High Altitude Research Station Jungfraujoch and Gornergrat Lukas ; 30 Lukas Sheffield, October 10-11,