Acknowledgments: my participation in CITES-2007 is funded by APN Chemistry of tropospheric tropospheric OH and HO OH and HO 2 radicals: Chemistry of 2 radicals: Current understanding and questions Current understanding and questions Yugo Kanaya (Frontier Research Center for Global Change, JAMSTEC) July 21, 2007 CITES-2007 conference, Tomsk, Russia 1
Importance of OH and HO OH and HO 2 Importance of 2 to atmospheric chemistry and climate to atmospheric chemistry and climate ▶ sink of anthropogenic/natural gases cleansing capacity (NOx, SO 2 , CO, hydrocarbons etc. ） ▶ sink of CH 4 and HCFCs global warming CH 4 + OH � products HCFC + OH � products ▶ Production of acidic species/aerosols acidification ・・・ SO 2 + OH � � H 2 SO 4 ▶ regional/hemispheric Catalytic production of tropospheric ozone pollution n CO h ν , O 3 OH HO 2 H 2 O n NO 2 NO n h ν , O 2 2 (n>1) O 3 n
Tropospheric Tropospheric OH known OH known only since only since 1969 1969 Weinstock, 1969 3
Current understanding of OH and HO OH and HO 2 chemistry Current understanding of 2 chemistry • Reactive, but not too reactive (do not react with O 2 ) • Short lifetime (<1 s for OH, <100 s for HO 2 ) • Regeneration via catalytic reactions • Concentration levels OH: 10 6 -10 7 radicals cm -3 , or ~0.1 pptv or ~1x10 -13 v/v HO 2 : 10 8 - 10 9 radicals cm -3 , or 10 pptv 4
Behavior of OH and HO 2 (1) Behavior of OH and HO 2 (1) • Diurnal variations • Non-linear behavior with NOx Logan et al., 1981 Logan et al., 1981 5
Behavior of OH and HO 2 (2) Behavior of OH and HO 2 (2) Spivakovsky et al., 2000 • Seasonal variations, geographical distributions of OH Unit: 10 5 cm -3 6
Current understanding of OH and HO OH and HO 2 chemistry Current understanding of 2 chemistry Key question: Key question: Any other important reactions controlling OH and HO 2 Any other important reactions controlling OH and HO 2 concentrations? concentrations? Our approach: Our approach: Direct measurements of OH and HO 2 Direct measurements of OH and HO 2 Comparison with modeled concentrations: Test the mechanisms Comparison with modeled concentrations: Test the mechanisms 7
In- -situ measurement techniques of OH situ measurement techniques of OH In See Heard and Pilling, 2003 for more details method Groups actively reporting observations in 2000s Chemical Ionization Mass 1. NCAR, USA Spectrometry (CIMS) 2. DWD, German Weather Service, Germany 3. Georgia Inst. Tech., USA Differential optical absorption 1. Forschungszentrum Juelich, Germany spectroscopy (DOAS) Laser-induced fluorescence 1. Leeds Univ., UK (LIF) at low pressure 2. Forschungszentrum Juelich, Germany 3. Pennsylvania State Univ., USA 4. FRCGC/JAMSTEC, Japan 5. Max Planck Institut, Germany 8
10cm diameter Quartz tube inlet （ Chemical Ionization/ CIMS （ Chemical Ionization/ CIMS OH mass spectrometry ） ） mass spectrometry 185nm for calibration Hg lamp OH + 34 SO 2 + M � H 34 SO 3 + M 34 SO 2 34 SO 4 H 2 H 34 SO 3 + O 2 � 34 SO 3 + HO 2 34 SO 3 + H 2 O + M � 34 SO 4 + M H 2 - ・ HNO 3 NO 3 - ・ HNO 3 - ・ HNO 3 + H 2 H 34 SO 4 34 SO 4 NO 3 - ・ HNO 3 + HNO 3 H 34 SO 4 � Highly sensitive but calibration QMS needed 9 Tanner et al., 1997
LP- -DOAS (long DOAS (long- -path differential optical absorption path differential optical absorption LP ） spectroscopy ） spectroscopy Dye laser spectro graph Free atmosphere Dorn et al., 1995 ( ) ( ) λ λ [ ] I ( ) I = ⋅ ⋅ ≈ − σ λ 0 ln l OH 1 ( ) ( ) λ λ I I 0 σ ( λ )~1x10 -16 (cm 2 ), l =3x10 5 (cm), [OH]=1x10 6 (cm -3 ) absorbance~3x10 -5 calibration not needed � 10
LIF instrument LIF instrument HO 2 + NO � OH + NO 2 to measure OH/HO 2 to measure OH/HO 2 190ns 490ns Detection limit @1min.: 2x10 5 cm -3 or 0.008 pptv 8kHz (or 8x10 -15 v/v) Kanaya et al., J. Atmos. Chem., 2001. Calibration uncertainty: 11 Kanaya and Akimoto, The Chem. Record, 2002 ± 20% (OH), ± 22% (HO 2 ) Kanaya and Akimoto, Appl. Opt., 2006
Field observations of OH and HO 2 in Japan Field observations of OH and HO 2 in Japan Chemical species technique (00, 6) (00, 6) O 3 UV absorption (03, 9) (03, 9) CO NDIR (98, 7- (98, 7 -8) 8) NO, NO 2 , NO y chemiluminescence NMHCs (C 2 -C 7 ) GC-FID, PTR-MS PANs GC-NICIMS (04, 1- -2) 2) (04, 1 HCHO, CH 3 CHO, Denuder, PTR-MS (04, 7- (04, 7 -8) 8) other oxygenated organic compounds (99, 7 (99, 7- -8) 8) (OVOC) T, RH (H 2 O), Conventional instruments, Pressure, J values spectroradiometer Colors: NO 2 column density (SCIAMACHY) Photochemical box model (Regional Atmospheric Chemistry Mechanism, 77 species, 237 reactions) Direct measurement of [OH], [HO 2 ] Modeled [OH], [HO 2 ] 12
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Kanaya et al., JGR, 2007a OH and HO 2 : Rishiri Rishiri Island Island OH and HO 2 : obs. model 14 12 10 [HO 2 ] (pptv) 8 6 4 2 0 10 7 10 7 Model constrained by HO 2 (obs.) 8x10 6 8x10 6 [OH] (cm -3 ) [OH] (cm -3 ) 6x10 6 6x10 6 4x10 6 4x10 6 2x10 6 2x10 6 0 0 18 18 19 19 20 20 21 21 22 22 23 23 24 24 25 25 26 26 27 27 28 28 29 29 Day of September 2003 Day of September 2003 14
25 OKI [HOx HOx] at coastal sites: ] at coastal sites: calc. [ 20 Aug. 6, 1998 obs. 15 10 4e+8 [HOx] (cm -3 ) 5 model 0 25 OKINAWA 20 Aug. 14, 1999 [HO 2 ] (pptv) 2e+8, Obs. ~8 ppt 15 10 5 0 0 Feb.16 Feb.15 25 RISHIRI Jun. 25, 2000 20 Sommariva et al., 2004 (Cape Grim) 15 10 5 Missing HO 2 sink: 0 1. HO 2 + aerosol reactions 0 2 4 6 8 10 12 14 16 18 20 22 0 15 2. Iodine chemistry Time of day Kanaya and Akimoto, 2002
1. Heterogeneous chemistry? 1. Heterogeneous chemistry? (b) Molecular Dynamics (MD) calculations on HO 2 pure water surface accommodated Taken up with the probability of 100% aerosol accommodated (aqueous particle) scattered α =497/500 =0.994 (a) Laboratory experiments with CuSO 4 -doped aqueous particles : accommodated γ ~ α > 0.5 (Mozurkewich et al., 1987) (Morita, Kanaya, and Francisco, JGR, 2004) 16
10000 Including heterogeneous Including heterogeneous loss in the model loss in the model SMPS 1000 dN/ dlogD HO 2 � lost on aerosol : k γ 100 OPC 10 1 1 10 100 1000 Kanaya et al., JGR, 2007a diameter (nm) obs. model 1. HO2 + aerosol reactions 14 12 10 [HO 2 ] (pptv) 8 6 4 2 17 0 18 19 20 21 22 23 24 25 26 27 28 29
2. Iodine chemistry? 2. Iodine chemistry? at Mace Head, Ireland, (Hebestreit, 2001) 18
Assuming γ (HOI)=0.5 Required IO: 10 -25 pptv 40 required IO (pptv) 30 20 10 0 19 23 24 25 26 27 28 29 day of September 2003
Tokyo in summer 2004: clean & smog periods Tokyo in summer 2004: clean & smog periods Aug.9 14:50 O 3 : 31 ppbv Aug. 12 12:50 O 3 : 114 ppbv 200 Smog Clean 150 (persistent southerly wind) (land-sea breeze) [O 3 ] (ppbv) 100 air quality standard 50 0 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 20 day of July/August 2004
Composite diurnal variations in Tokyo Composite diurnal variations in Tokyo 5x10 6 3.5 (b) winter OH (a) winter HO 2 4x10 6 3 3x10 6 [HO 2 ] (pptv) 2.5 [OH] (cm -3 ) 1.5x10 6 cm -3 2x10 6 2 1x10 6 1.5 1.1 pptv 0x10 6 1 -1x10 6 0.5 -2x10 6 0 2x10 7 70 (d) summer OH (c) summer HO 2 60 1.5x10 7 [HO 2 ] (pptv) 50 [OH] (cm -3 ) 1x10 7 40 6.3x10 6 cm -3 30 5x10 6 20 0x10 6 5.7 pptv 10 -5x10 6 0 0 2 4 6 8 10 12 14 16 18 20 22 0 0 2 4 6 8 10 12 14 16 18 20 22 0 Time of day (hour) Time of day (hour) 21
Kanaya et al., JGR accepted, 2007b OH, HO 2 comparisons winter 2004, Tokyo OH, HO 2 comparisons winter 2004, Tokyo 6x10 6 6x10 6 model obs. [OH] (cm -3 ) [OH] (cm -3 ) 4x10 6 4x10 6 2x10 6 2x10 6 0x10 0 0x10 0 20 20 21 21 22 22 23 23 24 24 25 25 26 26 27 27 28 28 29 29 29 29 30 30 31 31 1 1 2 2 3 3 4 4 5 5 6 6 7 7 6 6 5 5 4 4 [HO 2 ] (pptv) [HO 2 ] (pptv) [HO 2 ] (pptv) 3 3 2 2 1 1 0 0 -1 -1 20 20 21 21 22 22 23 23 24 24 25 25 26 26 27 27 28 28 29 29 29 29 30 30 31 31 1 1 2 2 3 3 4 4 5 5 6 6 7 7 Day of January/February 2004 Day of January/February 2004 Day of January/February 2004 22
Kanaya et al., JGR accepted, 2007b OH, HO 2 comparisons: summer 2004, Tokyo OH, HO 2 comparisons: summer 2004, Tokyo OH 1.4x10 7 1.2x10 7 model obs [OH] (cm -3 ) 10 7 8x10 6 6x10 6 4x10 6 2x10 6 0 -2x10 6 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 HO 2 60 obs model 50 [HO 2 ] (pptv) 40 30 20 10 0 23 26 27 28 29 30 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Day of July/August 2004
Kanaya et al., JGR revised, 2007c HO 2 at high [NO] during winter HO 2 at high [NO] during winter 10 [HO 2 ] obs F-D(Ox): net photochemical production rate of Ox model Ox := NO 2 + O 3 , [HO 2 ] (pptv) 1 F-D(Ox) = k [HO 2 ][NO] + Σ k i [RO 2 ] i φ i [NO] – k ’[O 1 D][H 2 O] – k ”[OH][O 3 ] – k ’”[HO 2 ][O 3 ] 0.1 – Σ k j [olefin] j [O 3 ] – k ””[OH][NO 2 ] ( 0900-1500 LST) (b) 0.01 1 10 100 14 100 F-D(Ox) model HOx (a) winter F-D(Ox) (ppbv h -1 ) 12 meas. HOx k[HO 2 ][NO] obs k[HO 2 ][NO] (ppbv h -1 ) model 10 10 8 6 4 1 2 0 0 2 4 6 8 10 12 14 16 18 20 22 0 0.1 24 1 10 100 time of day (hour) [NO] (ppbv)
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