Frontiers in quantum cascade laser based analysis of greenhouse gas stable isotopes

Transcription

1 Isotope - Ecology Course at the ETHZ 2018 Frontiers in quantum cascade laser based analysis of greenhouse gas stable isotopes Joachim Mohn joachim.mohn@empa.ch Air Pollution / Environmental Technology Laboratory

2 Empa an Institute of the ETH Domain Intro

3 Laboratory Air Pollution & Environmental Technology Intro Measurement Modelling Instrumental Development

4 Schedule Intro Introduction Motivation Basics of IR spectroscopy GHG analysis in the MIR CO 2 Isotopes Quantum cascade laser absorption spectroscopy 8 years measurement at Jungfraujoch CH 4 Isotopes TREX-QCLAS Pilot study at the Cabauw Tall Tower, NL N 2 O Isotopes Analytics: CRDS, OA-ICOS, TREX-QCLAS Benefit of continuous data Sub-urban N 2 O emissions, CH What s next??

5 Motivation Intro IPCC, Climate Change, The Physical Science Basis (2013) M. Meinshausen et al., Geosci. Model Dev. (2017) - + S. Toyoda et al. Mass Spectrometry Reviews (2015) M. Rigby et al. JGR (2012)

6 Spectroscopic techniques Basics > 1000 nm

7 Ro-vibrational analysis of gases Basics Most small molecules (e.g. CO 2, H 2 O, CH 4, N 2 O) absorb light in the near to mid IR Simultaneous excitation of vibrational and rotational modes 2140 cm -1 symmetric bending asymmetric stretch 3652 cm cm-1 stretch 3756 cm -1

8 Ro-vibrational analysis of gases Basics Most small molecules (e.g. CO 2, H 2 O, CH 4, N 2 O) absorb light in the near to mid IR Simultaneous excitation of vibrational and rotational modes 2140 cm -1 P9 P7 P5 R4 R6 R8 A A I log I 0 n L absorbance P3 R2 P1 R1 ( ) n L absorption cross section number density optical path length

9 GHG Analysis in the MIR Basics ppb N 2 O (x 10) 390 ppm CO ppm CH 4 (x 10) 100 ppb CO (x 10) wavenumber [cm-1]

10 CO 2 isotope analysis spectral range CO 2 Abundance wheighted linestrength [cm-1 / molecule cm-2] x10-21 x x cm O 13 C 18 O 0.39 % 16 O 13 C 16 O 1.11 % 16 O 12 C 16 O 98.4 % wavenumber [cm-1] δ 13 C - CO ( CO2/ CO2) sample ( OCO/ OCO) sample ( CO2/ CO2) δ O - CO reference ( OCO/ OCO) reference

11 CO 2 isotope analysis by QCLAS CO 2 (sample) 2 (reference) 1 (sample) (reference) laser current 3 measured simulation laser wavelength

12 CO 2 isotope analysis by QCLAS CO 2 Two sample standard deviation ( ) C 2008 (initial) 2012 (upgrade) t opt = 695 s O 2008 (initial) 2012 (upgrade) t opt = 840 s Averaging time (s) B. Tuzson et al. Appl. Phys. B (2008) P. Sturm et al. Atmos. Meas. Tech. (2013)

13 CO 2 isotope analysis Seasonal / diurnal cycles CO 2 Where does the CO 2 come from? P. Sturm et al. AMT (2013) M. Müller (in progress)

14 GHG Analysis in the MIR Intro ppb CO (x 10) 325 ppb N 2 O (x 10) ppm CH 4 (x 10) 390 ppm CO ppm CH 4 (x 10) wavenumber [cm-1]

15 CH 4 isotopologues CH 4 Abundance wheighted linestrength [cm-1 / molecule cm-2] x10-24 x x cm cm CH 3 D 0.06 % 13 CH4 1.1 % 12 CH % wavenumber [cm-1] δ 13 C - CH ( CH4/ CH4) sample (CH3D/CH4) sample ( CH4/ CH4) δd - CH reference (CH3D/CH4) reference

16 Analytical approach for ambient monitoring CH 4 TREX QCLAS 5-10 L ambient air ml target substance in synth. air S. Eyer et al. AMT (2016)

17 TRace gas Extration - TREX Trap: 90 cm, OD 4 mm tubing 2 g HayeSep D CH 4 Linear drive: aluminium stand-off max. thrust 110 N Stirling cooler: Weight: 3 kg MTTF: hrs Cold plate: 1.4 kg copper -210 C Vacuum chamber: turbomolecular pump 10-7 mbar

18 Laser spectroscopy CH 4 Absorption 300x Spectrum CH 4 CDH 3 13 CH4 [CH 4 ] = 600 ppm P = 20 Torr L = 7600 cm T = 296 K Linestrength (cm -1 /molecule cm -2 ) x Wavenumber (cm -1 ) two 7.7 µm MPC of 76 m optical path TEC MCT IR-detector Absorption 50x Spectrum CH 4 CDH [CH 4 ] = 600 ppm P = 20 Torr L = 7600 cm T = 296 K Linestrength (cm -1 /molecule cm -2 ) x10-24 Wavenumber (cm -1 )

19 Field campaign at Cabauw / NL TREX-QCLAS (Empa) 2 x IRMS (UU)

20 Temporal trends of CH 4 isotopologues CH 4 T. Röckmann et al. ACP (2016)

21 Atmospheric transport modelling CH 4 FLEXPART Emission inventory + D. W. Brunner et al. Geophysical Monograph Series (2012) 1500 Agriculture Waste Fossil Rest CH 4 [ppb] Relative contribution Date

22 CH 4 source signatures Emission events CH 4 T. Röckmann et al. ACP (2016)

23 CH 4 source signatures - Interpretation CH 4 T. Röckmann et al. ACP (2016)

24 GHG Analysis in the MIR Intro ppb CO (x 10) 325 ppb N 2 O (x 10) ppm CH 4 (x 10) 390 ppm CO ppm CH 4 (x 10) wavenumber [cm-1]

25 Analysis of N 2 O isotopomers N 2 O Abundance wheighted linestrength [cm-1 / molecule cm-2] x10-21 x10-21 x x to 2210 cm % 0.36 % 0.36 % 99 % 14 N 15 N 18 O 15 N 14 N 16 O 14 N 15 N 16 O 14 N 14 N 16 O wavenumber [cm-1] δ 15 N α ( ( N N α α / / N) N) sample reference site preference = 15 N - 15 N 15 N bulk = ( 15 N + 15 N )/2 IRMS Method: S. Toyoda and N. Yoshida (1999) Anal Chem (1999) C.A.M. Brenninkmeijer and T. Röckmann RCM (1999)

26 QCLAS N 2 O laser driving 10 ns pulses or cw operation pressure hpa scan rate 3 10 khz optical path m Absorbance 60x (a) transmission Line strength [cm -1 /(molecule cm -2 ] (b) N N O N N O N N O Wavenumber [cm -1 ] H. Wächter et al. Opt. Exp. (2008) line strength x N 14 N 16 O N 14 N 16 O wavenumber [cm -1 ] J. Heil et al. GCA (2014) E. Ibraim et al. IEHS (2017) in press 14 N 14 N 18 O 14 N 15 N 16 O

27 Different detection schemes N 2 O Direct absorption spectroscopy (QCLAS) Cavity ring-down spectroscopy (CRDS) Off-axis integrated cavity output Spectroscopy (OA-ICOS) G5101-i N 2 OIA-23e-EP 2188 or 2203 cm cm -1? 2188 cm -1? H. Wächter et al. (2008) Opt. Exp. Range: 2188 cm -1 J. Heil et al. (2014) GCA range: 2203 cm -3 Picarro Inc. (presentation). M. Gupota LGR Inc. (presentation)

28 Real time data abiotic N 2 O production N 2 O NO - 2 NH 2 OH Fe 3+ / Cu 2+ + O 2 +1 N 2 O abiotic N 2 O production from NH 2 OH: SP = J. Heil et al. GCA (2014)

29 Soil-emitted N 2 O N 2 O Denitrifikation + N 2 O Reduktion B. Wolf et al. Biogeosci. (2015)

30 N 2 O emission processes at a suburban site N 2 O E. Harris et al. JGR (2017)

31 N 2 O emission processes at a suburban site N 2 O E. Harris et al. JGR (2017)

32 Laser spectroscopy can provide Excellent selectivity & little sample preparation Continuous data for process studies Long-term unattended monitoring feasible to validate bottom up inventories Very high precision measurements required and spatio-temporally resolved source/isotope information What s next? Isotope - Ecology Course at the ETHZ 2018

33 Dual QC-lasers: Twin and Neighbor Outlook J. Jágerská et al. Optics Express (2015) M. Süess et al. Photonics 3, 2 (2016)

34 Clumped isotopes Outlook Abundance wheighted linestrength [cm-1 / molecule cm-2] x x x10-24 x10-24 x10-21 x10-21 x cm cm x x x x x x wavenumber [cm-1]

35 First Empa Outlook Thank you for your attention!