Chapter 12, Part 2. Fundamentals of Atmospheric Modeling

Transcription

1 verhead Slides for hapter 12, Part 2 of Fundamentals of Atmospheric Modeling by Mark Z. Jacobson Department of ivil & Environmental Engineering Stanford University Stanford, A January 30, 2002

2 Alkene Reaction With zone Ethene Ethene Ethene molozonide riegee biradical reaction 37% 63% + Formaldehyde riegee biradical + * Formaldehyde Excited riegee biradical (12.89) riegee biradical + N N 2 Formaldehyde (12.90) Excited criegee biradical decomposition 60% + 2 * 21% Excited riegee biradical * Excited formic acid 19% (12.91)

3 Alkene Reaction With zone Propene 7.5% + 3 Formaldehyde Methyl criegee biradical 2 3 Propene Propene molozonide % Formaldehyde % Acetaldehyde 3 * Excited methyl criegee biradical riegee biradical % + * Acetaldehyde Excited criegee biradical (12.92)

4 Alkene Reaction With zone Methylcriegee biradical reaction 3 Methyl criegee biradical + N N 2 3 Acetaldehyde (12.93) Excited methylcriegee biradical decomposition 3 * Excited methyl criegee biradical 3 * Excited acetic acid 16% % % (12.94)

5 Alkene Reaction With Nitrate Ethene --> nitrated organic radicals Ethene + N 3 N 2 Ethyl nitrate radical N Ethylperoxy nitrate radical + N N 2 N 2 Ethoxy nitrate radica (12.95) Propene --> nitrated organic radicals 3 Propene + N 3 N Propyl nitrate radical N Propylperoxy nitrate radical + N N 2 N 3 2 Propoxy nitrate radic (12.96)

6 Aromatic Reaction With ydroxyl Radical Toluene oxidation 8% Benzylperoxy radical 3 2 Benzyl radical 3 Toluene 92% Toluene-hydroxylradical adduct 3 o-ydroxytoluene + 2 o-resol (12.97)

7 Aromatic Reaction With ydroxyl Radical Benzylperoxy radical reaction with N 2 + N N 2 Benzoxy radical 2 Benzaldehyde Benzylperoxy radical + N 2 N Benzyl nitrate (12.98) Toluene-hydroxyl radical adduct reaction 3 + N 3 N 2 Toluene-hydroxyl radical adduct (12.99)

8 Fate of resol resol --> methylphenylperoxy radical and nitrocresol 3 +, Methylphenylperoxy radical o-resol N Methylphenoxy radical N m-nitrocresol (12.100)

9 Terpene Reaction With (1) 16.4% (4) 23.6% Isoprene 3 +, 2 (2) 12.3% (5) 21.2% (3) 12.3% (6) 14.1% Isoprene peroxy radicals (12.101) All six products convert N to N 2

10 Terpene Reaction With Methacrolein production via second product (12.102) N + 2 N Isoprene peroxy radical Methacrolein Formaldehyde Methylvinylketone production via fifth product (12.103) N + 2 N Isoprene peroxy radical Methylvinylketone Formaldehyde

11 Terpene Reaction With zone 2 3 Methylvinylketone + riegee biradical Methacrolein + riegee biradical 2 2 Isoprene 2 3 zonide product + Formaldehyde 3 2 zonide product + Formaldehyde (12.104)

12 Alcohol Reactions ydroxyl radical scavenges methanol (36-hour lifetime) + 85% Formaldehyde 2 15% Methanol Methoxy radical (12.105) ydroxyl radical scavenges ethanol (10-hour lifetime) 5% Ethanol + 90% 2 5% Acetaldehyde Ethoxy radical (12.106)

13 arbon Bond Lumping rganic gases lumped into surrogate groups. PAR (paraffins) -- Single carbon atoms with a single-bond between them LE (olefins) -- Terminal carbon atom pair with a double-bond between the two atoms ALD2 -- Non-terminal carbon atom pairs with a double bond attached to one of the carbons and terminal two-carbon carbonyl groups [-(=)] KET -- Single carbon ketone groups (=) TL (toluene) -- 7-carbon aromatics XYL (m-xylene) -- 8-carbon aromatics ISP (isoprene) -- Terpenes UNR -- Unreactive

14 arbon Bond Lumping (Table 12.7) hemical Name arbon Bond Group hemical Structure Ethane 0.4 PAR +1.6 UNR Ethene 1 ET Formaldehyde 1 FRM hemical Name arbon Bond Group hemical Structure n-butane 4 PAR Trans 2-butene 2 ALD2 Acetaldehyde 1 ALD2 hemical Name arbon Bond Group hemical Structure 2,2,4-Trimethylpentane 8 PAR Propene 1 PAR + 1 LE Propionaldehyde 1 PAR + 1 ALD2 hemical Name arbon Bond Group hemical Structure yclopentane 5 PAR Ethyne 1 PAR + 1 UNR Benzaldehyde 1 ALD2 + 5 UNR 2 3 Toluene 1 TL 3 Ethylbenzene 1 PAR + 1 TL 3 2 m-xylene 1 XYL 3 1,2,3- Trimethylbenzene 1 PAR + 1 XYL

15 Stratospheric hemistry zone mixing ratios stratosphere free troposphere urban air 10 ppmv 40 ppbv ppmv zone production in the stratosphere xygen photolysis 2 + hν λ < 175 nm ( 1 D) + (12.107) 2 + hν < λ < 245 nm (12.108) zone formation M ( 1 D) (12.109) M 3 + M (12.110) zone photodissociation 3 + hν 2 + ( 1 D) λ < 310 nm (12.111) 3 + hν 2 + λ > 310 nm (12.112)

16 zone Destruction by Nx Nitrous oxide reaction: 10% of N 2 destruction N 2 + ( 1 D) 64% 2N 36% N (12.113) Nitrous oxide photolysis: 90% of N 2 destruction (12.114) N 2 + hν N 2 + ( 1 D) λ < 240 nm N catalytically destroys ozone in the upper stratosphere N + 3 N (12.115) N 2 + N + 2 (12.116) (12.117)

17 zone Destruction by x ydroxyl radical formation in stratosphere ( 1 D) (12.118) catalytically destroys ozone in the lower stratosphere (12.119) (12.120) (12.121)

18 Removal reactions Removal of x and Nx (12.122) M N 2 + N 3 (12.123) M 2 + N 2 2 N 2 (12.124) Nitric acid and peroxynitric acid photodissociation is slow Source of Water Vapor (12.125) Methane and carbon monoxide reactions in the stratosphere are similar to those in the free troposphere

19 hlorine Emissions to Stratosphere Table WM (1994) hemical Formula Trade Name hemical Name Percent ontribution to Stratospheric Emissions Anthropogenic Sources F 2 l 2 F-12 Dichlorodifluoromethane 28 Fl 3 F-11 Trichlorofluoromethane 23 l 4 arbon tetrachloride 12 3 l 3 Methyl chloroform 10 Fl 2 F 2 l F Fluorodichloro,2- difluorochloroethane 6 F 2 l F-22 hlorodifluoromethane 3 Natural Sources 3 l --- Methyl chloride 15 l --- ydrochloric acid 3 Total 100%

20 zone Destruction by hlorine Photolysis of chlorinated compounds above 20 km l l F l + hν F + l λ < 250 nm l l (12.126) l l F l + hν F + l λ < 230 nm F F (12.127) l l l l + hν l + l λ < 250 nm l l (12.129) l + hν + l λ < 220 nm (12.130) Methyl chloride scavenging by hydroxyl radical l + l 2 (12.128)

21 zone Destruction by hlorine atalytic ozone destruction by chlorine l + 3 l + 2 (12.131) l + l + 2 (12.132) (12.133) nly 1% of chlorine is typically active as l or l.

22 Removal of Active hlorine Removal of l and l 4 l + 3 l + 2 l l l + 2 (12.134) M l + N 2 l N hlorine monoxide hlorine nitrate (12.135) l hlorine monoxide + 2 l 2 ypochlorous acid (12.136)

23 Removal of Active hlorine l reservoir leaks hν + l λ < 220 nm l + l + 2 l + (12.137) ln 2 reservoir leaks l N + hν l + N λ < 400 nm hlorine nitrate l reservoir leaks Nitrate radical (12.138) l + hν l + λ < 375 nm (12.139)

24 zone Destruction by Bromine 3 Br = methyl bromide (produced biogenically in the oceans and anthropogenically as soil fumigant) Photolysis of methyl above 20 km Br + hν + Br λ < 260 nm (12.140) atalytic ozone destruction by bromine Br + 3 Br + 2 (12.141) Br + Br + 2 (12.142) (12.143)

25 Removal of Active Bromine Removal of Br and Br Br + 2 Br Br + 2 (12.144) M Br + N 2 Br N Bromine monoxide Bromine nitrate (12.145) Br and BrN 2 reservoir leaks Br + Br + 2 (12.146) Br N + hν Br + N λ < 390 nm Bromine nitrate Nitrate radical (12.147)

26 zone Regeneration Figs a, b. Time-evolution of modeled profile of ozone (a) mixing ratio and (b) number concentration at 34 o N latitude, starting with zero ozone our 1 our 6 our 24 Day 5 Day 50 Day 464 Altitude (km) Altitude (km) zone volume mixing ratio (ppmv) zone (10 11 molecules cm -3 )

27 Regeneration Rate of the Global zone Layer Fig hange in ozone column abundance, averaged over the globe, during two global model simulations in which chlorine was present and absent, respectively. In both cases, ozone was initially removed from the model atmosphere. Avgerage global ozone column (Dobson units) No chlorine 250 With chlorine /1 1/7 4/17 7/26 11/4 Day and date of simulation

28 zone ole Growth Table Minimum measured values of ozone column abundances and areal extent of the ozone hole over Antarctic region from Data from NASA Goddard Space Flight enter. The area of the Antarctic is about 13 million km 2 and the area of North America is about 24 million km 2. zone Minima (DU) Size (million km 2 )

29 Polar Stratospheric loud Reactions Type I Polar Stratospheric louds (PSs) nitric acid and water temperature of formation < 195 K diameter µm number concentration 1 partic. cm -3 Type II Polar Stratospheric louds Water ice temperature of formation < 187 K diameter µm number concentration 0.1 partic. cm -3 Reactions on Polar Stratospheric loud Surfaces ln 2 (g) + 2 (a) l(g) + N 3 (a) (12.148) ln 2 (g) + l(a) l 2 (g) + N 3 (a) (12.149) N 2 5 (g) + 2 (a) 2N 3 (a) (12.150) N 2 5 (g) + l(a) ln 2 (g) + N 3 (a) (12.151) l(g) + l(a) l 2 (g) + 2 (a) (12.152)

30 Surface Reaction Rates First-order rate coefficient (s -1 ) k s,q = 1 4 v qγ q a (12.153) Thermal velocity of impinging gas (cm s -1 ) v q = 8k B T πm q 1 2 (12.154) Table Estimated reaction probabilities for the gases in reactions (12.147) - (12.151) on Type I and II PS surfaces. Data from DeMore et al. (1997) and references therein. Reaction Type I PSs Type II PSs ln 2 (g) + 2 (a) ln 2 (g) + l(a) N 2 5 (g) + 2 (a) N 2 5 (g) + l(a) l(g) + l(a)

31 Polar zone Destruction l 2 and l photolysis in early spring l 2 + hν 2l λ < 450 nm (12.164) l + hν l + λ < 375 nm (12.165) hlorine nitrite photolysis in early spring ln 2 + hν l + N 2 λ < 370 nm (12.166) atalytic ozone destruction by dimer mechanism 2 x ( l + 3 l + 2 ) (12.167) l + l M l 2 2 (12.168) l hν l + l λ < 360 nm M l l + 2 (12.170) (12.171)

32 Polar zone Destruction A second catalytic cycle that involves bromine l + 3 l + 2 (12.172) Br + 3 Br + 2 (12.173) Br + l Br + l + 2 (12.174) (12.175)

33 onversion of hlorine Reservoirs to Active hlorine Fig % l, l 37% ln 2 62% l Before PS and photolysis reactions ln 2 l l, l After PS and photolysis reactions