We think you have liked this presentation. If you wish to download it, please recommend it to your friends in any social system. Share buttons are a little bit lower. Thank you!
Presentation is loading. Please wait.
Published byHeaven Hollings
Modified about 1 year ago
Copyright © 2010 R. R. Dickerson1 LECTURE 20 Atmospheric Odd Hydrogen, HOx AOSC 637 Spring 2010 Atmospheric Chemistry Russell R. Dickerson
Odd Hydrogen: Outline Importance Chemistry Sources Sinks Reservoirs and Ratios Detection Techniques Fluorescence FAGE DOAS Chem Amplification Global Budget Calculations Remaining Challenges Bibliography
Copyright © 2010 R. R. Dickerson3 Odd Hydrogen Importance: Ozone destruction in both the stratosphere and trospsphere. Removal of NOx, ClOx, CO, VOC’s, SOx, HCFC’s The most important species for transformations. Many pollutants have no other sink. Chemistry Sources (remember what HCO and H do)
Copyright © 2010 R. R. Dickerson4 HYDROCARBRONS REACTIVITY FOR URBAN SMOG (OZONE) FORMATION HYDROCARBONk(O) k(O ₃ ) k(OH) (All units: cm³s ⁻ ¹) Methane, CH ₄ 1.1x10 ⁻ ¹ ⁷ SLOW 7.9x10 ⁻ ¹ ⁵ Ethane, C ₂ H ₆ 9.6x10 ⁻ ¹ ⁶ SLOW 2.7x10 ⁻ ¹³ Propane, C ₃ H ₈ 1.5x10 ⁻ ¹ ⁴ SLOW 1.2x10 ⁻ ¹² Butane, C ₄ H ₁₀ 3.1x10 ⁻ ¹ ⁴ SLOW 2.3x10 ⁻ ¹² Hexane, C ₆ H ₁₄ 9.5x10 ⁻ ¹ ⁴ SLOW 5.7x10 ⁻ ¹² 2,3 Dimethyl butane (C ₆ H ₁₄ ) 2.1x10 ⁻ ¹³ SLOW 6.3x10 ⁻ ¹² Ethene, C ₂ H ₄ 8.4x10 ⁻ ¹³1.8x10 ⁻ ¹ ⁸ 8.0x10 ⁻ ¹² Propene, C ₃ H ₆ 3.6x10 ⁻ ¹²1.1x10 ⁻ ¹ ⁷ 2.5x10 ⁻ ¹¹ Benzene, C ₆ H ₆ 1.6x10 ⁻ ¹ ⁴ SLOW 1.2x10 ⁻ ¹² Toluene, C ₇ H ₈ 5.9x10 ⁻ ¹ ⁴ SLOW 6.4x10 ⁻ ¹²
Copyright © 2010 R. R. Dickerson5 Odd Hydrogen To calculate OH we need: j(O 3 ), [O 3 ], [H 2 O] Sinks
Copyright © 2010 R. R. Dickerson6 Reservoir species, control ratios of OH/HO 2
Copyright © 2010 R. R. Dickerson7 RONO 2
Copyright © 2010 R. R. Dickerson8 Steady State Approximations: From Logan, JGR (1981)
Copyright © 2010 R. R. Dickerson9 Calculated mean OH (x10 -6 cm -3 ) in a CH 4, CO, O 3 atmosphere, from Crutzen’s model at MPI. Why does het max occur in the LFT in the tropics?
Copyright © 2010 R. R. Dickerson10 Potential Energy Curves for OH Chem. Phys. 237(1-2), 123-138 (1998) DOI:10.1016/S0301-0104(98)00219-5
Copyright © 2010 R. R. Dickerson11 Solar flux induced fluorescence was successful for the detection of OH in the Stratosphere (Anderson JGR, 7820, 1971). Anderson put a scanning spectrometer on the nose of a rocket and measured the emission at 308 nm due to solar excitation. In situ resonance fluorescence with a microwave discharge lamp worked in the strat (Anderson GRL, 1976), but not in the trop.
Copyright © 2010 R. R. Dickerson12 FAGE, Fluorescence Assay by Gas Expansion, is essentially laser-induced fluorescence at low pressure.
Copyright © 2010 R. R. Dickerson13 Radiation at 308 nm photolyzes O 3 to O( 1 D). Early attempts to measure OH via fluorescence failed – why?
Copyright © 2010 R. R. Dickerson14
Copyright © 2010 R. R. Dickerson15
Copyright © 2010 R. R. Dickerson16 Diurnal variation of OH measured using LIF (o) and DOAS () during POPCORN (Adapted from Hofzumahaus et al., 1998).
Copyright © 2010 R. R. Dickerson17 Correlation plot of all LIF OH data versus the photolysis frequency of ozone, j(O 1 D). (Adapted from Holland et al., 1998).
Copyright © 2010 R. R. Dickerson18
Copyright © 2010 R. R. Dickerson19 Atmospheric absorption spectra measured using DOAS as a function of time of day (UT). Solid lines are reference absorption spectra of OH radicals fitted to the measurements (Adapted from Dorn et al., 1996).
Copyright © 2010 R. R. Dickerson20
Copyright © 2010 R. R. Dickerson21 Dependence of the measured OH concentration on NO 2 during the POPCORN field campaign. To make this behavior visible, the OH data were first normalized with respect to j(O 1 D) and then plotted versus equal log(NO 2 )-intervals of 0.1. Full curve corresponds to the model-calculated dependence. [Adapted from Ehhalt, 1999].
Copyright © 2010 R. R. Dickerson22 Comparison of observed and calculated OH concentrations versus NO X during the 1993 Idaho Hill experiment (THOPE). The different model calculations account for different amounts of unmeasured biogenic hydrocarbons [Adapted from McKeen et al., 1997].
Copyright © 2010 R. R. Dickerson23 Altitude profiles of measured (open circles) and modeled OH for 10 May 1996 during SUCCESS. Measurements and models are averaged into 0.5 km altitude bins. Models with (dash- dot line) and without (dashed line) acetone are compared. (Adapted from Brune et al., 1998). CH 3 C(O)CH 3 + hv → 2CH 3 + CO
Copyright © 2010 R. R. Dickerson24 Calculated mean OH (x10 -6 cm -3 ) in a CH 4, CO, O 3 atmosphere, from Crutzen’s model at MPI. Why does het max occur in the LFT in the tropics?
Copyright © 2010 R. R. Dickerson25 Horowitz et al., JGR 2003.
Copyright © 2010 R. R. Dickerson26 Prinn et al., Science, 1995. Global mean OH can be calculated from the rate of loss of methyl chloroform, CCl 3 CH 3
Copyright © 2010 R. R. Dickerson27 Concentrations of CCl 3 CH 3 continue to fall.
Copyright © 2010 R. R. Dickerson28 From NOAA Earth System Research Laboratory http://www.esrl.noaa.gov/gmd/ odgi/
Copyright © 2010 R. R. Dickerson29 Calculating Global Mean OH from CH 3 CCl 3 Concentrations Because OH is so hard to measure, we would like to get at the concentration another way [ Prinn et al., 1987; Prinn et al., 1995]. Let’s designing a good experiment – a good OH tracer must have: 1.Only one sink – reaction with OH 2.A lifetime » inter-hemispheric mixing » seasonal variations in OH 1.Well known atmospheric burden 2.Well known production rate 3.Well known rate const, k OH 4.A reliable, precise measurement technique.
Copyright © 2010 R. R. Dickerson30 In the original work, Prinn performed a simple global burden calculation of mean [OH]. 1.Assume steady state, i.e., production = loss. 2.Measured or calculated production rate. 3.Loss (= production) = k OH [CH 3 CCl 3 ][OH] 4.Assume [CH 3 CCl 3 ] is constant in time and space (we’ll revisit this later).
Copyright © 2010 R. R. Dickerson31 In the original work, Prinn performed a simple global burden calculation of mean [OH]. 1.Assume stready state, i.e., production = loss. 2.Measured or calculated production rate. 3.Loss (= production) = k OH [CH 3 CCl 3 ][OH] 4.Assume [CH 3 CCl 3 ] is constant in time and space. First order estimate (box model) CH 3 CCl 3 + OH → H 2 O + CH 2 CCl 3 k OH = 1.64x10 -12 e (-1520/T) Mean middle trop temp ~ 255 K; k 255 = 4.2x10 -15 cm 3 s -1
Copyright © 2010 R. R. Dickerson32 What was the mean [CH 3 CCl 3 ]? LatutudeMixing Ratio (in 1981) 52°N169 (ppt) 45°N163 13°N147 14°S122 41°S117 Lat weighted mean144 ±25 ppt Total tropospheric burden = mass of atmosphere x mean mixing ratio x ratio of molecular weights. 4.0x10 21 g x 1.44x10 -10 x 133.5/29 = 2.65x10 12 g From Prinn et al., (1983).
Copyright © 2010 R. R. Dickerson33 What was the mean [CH 3 CCl 3 ]? The global production rate in 1981 was ~5.0x10 11 (±0.5) g yr -1 We don’t know for sure that release = production.
Copyright © 2010 R. R. Dickerson34 What was the uncertainty mean [OH] of 1.4x10 6 cm -3 ? 1.Rate Constant ±15% 2.Absolute concentration ± 20% 3.Production rate ± 10% 4.Mean global conc ± 25% 5.Annual variation ± 30% RMS ±50% Using a 12-box model, the global mean OH was estimated to be 9.7 ± 0.5x10 5 cm -3 in 1994 with little temporal change by Prinn et al., 1995. They also derived a residence timje for methylchloroform of 4.8 yr.
Copyright © 2010 R. R. Dickerson35 Remaining challenges I.What are the controlling factors in the upper trop.? II.Is the mean OH derived from methyl chloroform correct in light of recent discoveries about Cl chemistry in the trop? III.How will changes in the composition and climate impact the atmosphere’s oxidizing capacity and what unintended consequences await us?
Copyright © 2010 R. R. Dickerson36 Bibliography Anderson, J.G., The absolute concentration of OH (X 2 P) in the earth's stratosphere, Geophys. Res. Lett. 3, 165-168, 1976. Brune, W.H. et al., Airborne in-situ OH and HO 2 observations in the cloud-free troposphere and lower stratosphere during SUCCESS, Geophys. Res. Lett., 25, 1701-1704, 1998. Ehhalt, D.H., Photooxidation of trace gases in the troposphere, Phys. Chem. Chem. Phys., 1, 5401-5408, 1999. McKeen et al., Photochemical modeling of hydroxyl and its relationship to other species during the Tropospheric OH Photochemistry Experiment, J. Geophys. Res., 102, 6467-6493, 1997. Dorn, H. P., U. Brandenburger, T. Brauers, M. Hausmann, and D. H. Ehhalt, In-situ detection of tropospheric OH radicals by folded long- path laser absorption. Results from the POPCORN field campaign in August 1994., Geophys. Res. Lett., 23, 2537-2540, 1996. Hard, T.M., L. A. George, and R. J. O'Brien, FAGE Determination of Tropospheric HO and HO 2, J. Atmos. Sciences, 52, 3354-3372, 1995. Hausmann, M., U. Brandenburger, T. Brauers, and H.-P. Dorn, Detection of tropospheric OH radicals by long-path differential-optical-absorption spectroscopy: Experimental setup, accuracy, and precision, J. Geophys. Res., 102, 16011-16022, 1997. Logan, J. A., M. J. Prather, S. C. Wofsy, and M. B. McElroy (1981), Tropospheric chemistry: A global perspecvtive, J. Geophys. Res., 86, 7210-7254. Prinn, R., D. Cunnold, R. Rasmussen, P. Simmonds, F. Alyea, A. Crawford, P. Fraser, and R. Rosen (1987), Atmospheric trends in methylchloroform and the global average for the hydroxyl radical, Science, 238, 945-950. Prinn, R. G., R. F. Weiss, B. R. Miller, J. Huang, F. N. Alyea, D. M. Cunnold, P. J. Fraser, D. E. Hartley, and P. G. Simmonds (1995), Atmospheric Trends and Lifetime of CH 3 CCl 3 and Global OH Concentrations, Science, 269, 187-192.
LECTURE 12 AOSC 434 AIR POLLUTION RUSSELL R. DICKERSON.
Copyright © 2014 R. R. Dickerson & Z.Q. Li 1 Spectroscopy and Photochemistry AOSC 620 R. Dickerson Fall 2015.
TROPOSPHERIC OZONE AND OXIDANT CHEMISTRY Troposphere Stratosphere: 90% of total The many faces of atmospheric ozone: In stratosphere: UV shield In middle/upper.
METO 621 CHEM Lesson 4. Total Ozone Field March 11, 1990 Nimbus 7 TOMS (Hudson et al., 2003)
Oxygen Atom Recombination in the Presence of Singlet Molecular Oxygen Michael Heaven Department of Chemistry Emory University, USA Valeriy Azyazov P.N.
Fundamentals of air Pollution – Atmospheric Photochemistry – Part B Yaacov Mamane Visiting Scientist NCR, Rome Dec May 2007 CNR, Monterotondo, Italy.
Generic structure: Leaky water tank A model for atmospheric methyl chloroform C 2 H 3 Cl 3.
Generic structure: Leaky water tank and applications John Sternam from MIT argues the importance.
METO 621 CHEM Lesson 2. The Stratosphere We will now consider the chemistry of the troposphere and stratosphere. There are two reasons why we can separate.
This Week—Tropospheric Chemistry READING: Chapter 11 of text Tropospheric Chemistry Data Set Analysis.
THE ATMOSPHERE: OXIDIZING MEDIUM IN GLOBAL BIOGEOCHEMICAL CYCLES EARTH SURFACE Emission Reduced gas Oxidized gas/ aerosol Oxidation Uptake Reduction Atmospheric.
4/20/2006Ga Tech - EAS Air Chemistry Group Presentation 1 A Hydrogen Economy’s Potential Environmental Impacts Chun Zhao Evan Cobb.
METO 621 Lesson 21. The Stratosphere We will now consider the chemistry of the troposphere and stratosphere. There are two reasons why we can separate.
CHAPMAN MECHANISM FOR STRATOSPHERIC OZONE (1930) O O 3 O2O2 slow fast Odd oxygen family [O x ] = [O 3 ] + [O] R2 R3 R4 R1.
1May 14, 2014 Uncertainties in projections of ozone- depleting substances and alternatives Guus Velders The Netherlands (RIVM)
METO 637 Lesson 16. Sulfur chemistry The abundances, sources, budgets, and photochemistry of atmospheric sulfur compounds are poorly understood compared.
Measurement of the Long-term trends of Methanol (CH 3 OH) and Carbonyl Sulfide (OCS) Both methyl chloride and carbonyl sulfide have strong infrared bands.
Near-Infrared Photochemistry of Atmospheric Nitrites Paul Wennberg, Coleen Roehl, Geoff Blake, and Sergey Nizkorodov California Institute of Technology.
1 UIUC ATMOS 397G Biogeochemical Cycles and Global Change Lecture 5: Atmospheric Structure / Earth System Don Wuebbles Department of Atmospheric Sciences.
1 Biogenic Hydrocarbons Lecture AOSC 637 Atmospheric Chemistry Russell R. Dickerson Finlayson-Pitts Chapt. 6 & 9 Seinfeld Chapt. 6 OUTLINE History Nomenclature.
The Atmosphere: Oxidizing Medium In Global Biogeochemical Cycles EARTH SURFACE Emission Reduced gas Oxidized gas/ aerosol Oxidation Uptake Reduction.
Overview of UT/LS Science Issues and New Information from SEAC4RS Steve Wofsy and Jasna Pittman – Harvard University Qing Liang – NASA Goddard Space Flight.
Simple Chemical modeling of ozone sensitivity to NOx and VOCs in Atlanta Jin Liao EAS /24/2007.
1 UIUC ATMOS 397G Biogeochemical Cycles and Global Change Lecture 14: Methane and CO Don Wuebbles Department of Atmospheric Sciences University of Illinois,
Ozone Budget From: Jacob. Ozone in the Atmosphere Lifetime: –~1 month –Highly variable – dependent on season, latitude, altitude, etc. Background concentrations:
Global trends in CH 4 and N 2 O Matt Rigby, Jin Huang, Ron Prinn, Paul Fraser, Peter Simmonds, Ray Langenfelds, Derek Cunnold, Paul Steele, Paul Krummel,
Tropospheric Ozone Chemistry David Plummer presented at the GCC Summer School Montreal, August 7-13, 2003 Outline: - Solar radiation and chemistry - Tropospheric.
Photochemical transformation reactions Direct photolysis = transformation of a compound due to its absorption of UV light Indirect photolysis = transformation.
Study of the Atmospheric Degradation, Radiative Forcing and Global Warming Potentials of CH 2 FCH 2 OH, CHF 2 CH 2 OH and CF 3 CH 2 OH S. R. Sellevåg a,
Atmospheric Chemistry Experiment (ACE): Organic Molecules from Orbit Peter Bernath Department of Chemistry, University of York Heslington, York, UK.
The Stratospheric Chemistry and The Ozone Layer *Stratospheric circulation *Stratospheric photochemistry *Gas phase reactions *Ozone and Catalytic cycles.
METO 621 Lesson 24. The Troposphere In the Stratosphere we had high energy photons so that oxygen atoms and ozone dominated the chemistry. In the troposphere.
CHAPTER 10: STRATOSPHERIC CHEMISTRY. THE MANY FACES OF ATMOSPHERIC OZONE Troposphere Stratosphere: 90% of total In stratosphere: UV shield In middle/upper.
METO 637 Lesson 14. Photochemical chain initiation In the troposphere several species are present that absorb solar ultraviolet radiation and can initiate.
METO 637 Lesson 6. The Stratosphere We will now consider the chemistry of the troposphere and stratosphere. There are two reasons why we can separate.
10-11 October 2006HYMN kick-off TM3/4/5 Modeling at KNMI HYMN Hydrogen, Methane and Nitrous oxide: Trend variability, budgets and interactions with the.
A modelling study on trends and variability of the tropospheric chemical composition over the last 40 years S.Rast(1), M.G.Schultz(2) (1) Max Planck Institute.
Atmospheric chemistry Day 4 Air pollution Regional ozone formation.
Seasonal variability of UTLS hydrocarbons observed from ACE and comparisons with WACCM Mijeong Park, William J. Randel, Louisa K. Emmons, and Douglas E.
QUESTIONS 1. How does the thinning of the stratospheric ozone layer affect the source of OH in the troposphere? 2. Chemical production of ozone in the.
Trace Gas Measurements in India S. Lal Physical Research Laboratory, Ahmedabad, India Indo-US Workshop Chennai July 12-16, 2006.
SETTING THE STAGE FOR: BIOSPHERE, CHEMISTRY, CLIMATE INTERACTIONS.
Sinks Mathew Evans, Daniel Jacob, Bill Bloss, Dwayne Heard, Mike Pilling Sinks are just as important as sources for working out emissions! 1.NO x N 2 O.
Ref: D. Fahey, adapted from IPCC 4th Assessment, Summary for Policymakers, Feb. 2, 2007 WHAT ARE THE MAJOR HUMAN & NATURAL ACTIVITIES FORCING CLIMATE CHANGE.
Lecture 4 Radiation Basics AOSC 434 AIR POLLUTION RUSSELL R. DICKERSON 1.
Atmospheric chemistry Lecture 2: Photochemistry & kinetics Dr. David Glowacki University of Bristol,UK
Copyright © 2010 R. R. Dickerson & Z.Q. Li 1 AOSC 620 The Ozone Hole R. Dickerson.
A missing sink for radicals Jingqiu Mao (Princeton/GFDL) With Songmiao Fan (GFDL), Daniel Jacob (Harvard), Larry Horowitz (GFDL) and Vaishali Naik (GFDL)
QUESTIONS 1.Based on the major source of OH described last class where do you expect OH formation to be high? 2.Why don’t reactions of hydrocarbons deplete.
© 2017 SlidePlayer.com Inc. All rights reserved.