SPTP MESO MODELING
SPTP MESO MODELING ATMO 689
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Date Created: 10/21/15
Some important relationships Optical Density OD l l0 x 1000 OD 010 IE Lambert Beer s Law I0 transmission 1 path length C concentration 0 0A specific absorptivity or absorption cross section Energy of absorptionemission is discrete Ephoton ortransition hv h cA h Planck s constant Nonelectronic transitions require a permanent or inducible dipole macroscopic analogy a moving charge creates an alternating electric field that sends out a wave N2 and 02 do neither have a permanent dipole such as H20 nor an induced dipole gt no vis IR absorption SI Dissociation photolysis energy has to exceed bonding energy ie hCx gt Ebond Figure 77 Schematic representation of the sequence of events leading to fluorescence triplet formation and phosphorescence Note that the maximum in the fluorescent spectrum again will correspond to the transition with the largest Franck Condon factor from Boeker and van Grondelle Environmental Physics Oxvqen electronic states v 4 iii OFF 039 579 tnergy KJ FIG Sohu 1955 URE 41 Potential energy curves for ground and rst four ed stutes of 2 SeR SchumanneRungc system H berg continuum AeA atmospheric bands adapted from Gay 1968 from FinlaysonPitts and Pitts Chemistry of the upper and lower Atmosphere Oxvqen absorption spectrum WAVELENGTH I nm FIGURE 26 Ultraviolet absorption spectrum of molecular oxygen with cross sections given in cm2 molecule 1 Data compiled from Ackerman and Biaum 1970 Ditchburn and Young 1962 Hudson er al 1900 Ogawa 1971 shardanand 1969 Shardanand and Rao 1977 and Wamnabe et al 1953 from Warneck Chemistry of the Natural Atmosphere Qz UVIight absorption TABLE 41 Absorption Cross Sections Base e for 02 between 205 and 240 nm a m Wavelength 2 10240 1 Wavelength l is 22 3 600 8 nm em molecule urn cm molecule 1 5i B 205 735 223 3189 Tm V 39 206 713 224 367 3 3 7 39 100 L 207 705 225 345 g g 208 186 226 321 g R 209 668 227 298 N E 210 651 228 277 g E 211 024 229 263 6 037 10 a 212 6105 230 243 w E 213 580 231 225 E 214 572 232 210 39 I I I I 215 5159 233 194 03907 I30 150 170 2 216 535 234 178 Wavelength nm 217 513 235 163 218 488 236 148 FIGURE 42 Absorption coef cients for O1 in the 219 464 237 134 Schumann Rouge continuum Note log scale Adapted from Inn 220 446 Z3 122 195539 221 426 239 110 222 409 240 1 01 From DeMore at Ill 1997 recommendations based on Yoshino 1141 Planet Space Sui 36 1469 1988 from Finlayson Pitts and Pitts Chemistry of the upper and lower Atmosphere Q2 NIRvis absorption 61 IE 1021 3 1022 HZ I g 10 23 v 0 an O 724 I g E 10 V1 I I NE 10 25 7 VED U 10 26 1027 H 9 T0728 I I I I I I E 400 600 800 1000 1200 14 0 b N 0 4x10 3 o OX gtO AVX f 3x10 45 I I2 g a E 45 29 Ag v 3 2x10 L HII IAQMQM g 1045 Ii zgwwijm 02N2 w 210 A ll 9 0 AAA I I I 0 400 600 800 1000 T200 1400 7 nm FIGURE 46 AbsurpLinn bands of a Z and b collisioninduced absorptions of 02 with Oz and 0139 the 126an band with N2 respectively adapted from Solomon 9 11 1998 from FinlaysonPitts and Pitts Chemistry of the upper and lower Atmosphere Relevance for Atmospheric Chemistry AB hp gtAB gt AB is an exited often unstable state of molecule AB for an electronic transition due to absorption of UV vis light AB has a different electron configuration than AB for an infrared absorption AB rovibrates stronger than AB are processes of the following relative importance in the atmosphere 1 thermal nonradiative decay eg greenhouse heating 2 photolysis eg oxygen or ozone in stratosphere 3 fluorescence eg NO in thermosphere 4 phosphorescence negligible 5 others eg chemical reaction negligible VB 667 cm 1 VAS 2349 cm1 Stretching modes Bending modes Figure 74 Representation of the two stretching modes and the two bending modes of 002 For the stretching modes we indicated three different positions The bending modes correspond to two orthogonal planes which are physically equivalent and therefore have the same frequency from Booker and van Grondelle Environmental Physics Homework tasks Why does thermal decay usually dominate over mechanisms of excess energy loss How could fluorescence be boosted think about both the molecule itself and its environment If so where do you think nitrogen N2 is photolyzed Can you explain why certain transitions of the oxygen molecule have higher probability of success stronger absorption lines than others is your head spinning yet 002 is a strong CO is a weak IR absorber Suggest possible reasons for that fact Hvdrocarbon Oxidation Mechanisms III OH 0 i CH3CH2CH CH2 OH CHSCHZCH CHZOO39 NO No2 iH OH Isomerization I 1 L641 shift CHSCH2CHCHZO M 02 Of Decomposi on H 39OOCHQCHZCHCHZQH NO 39CHZCHZCH CHZOH NO2 H ijiHo2 OCHZCHZCH CHZOH c CH2CH0HCHZOH O 3 4 Dihydroxybutanal Ozonealkene reactions cal16 03 M CH30HO CHZOO or CHSCHOO HCHO so 0 dz H23 CHCH3 primafy d O on e N a RIRZCO R3R4COO lt7 Criegee intermediate R3R4CO R1R3C00 H Criegee intermediate OH Reactivity of Hydrocarbons TABLE 165 011 Reactivity Scale for Hydrocarbons k a Class 29HK 79 Typical hydrocarbons I SS X 10714 2100 days CH4 II 8 80 X 10 14 10100 days Acetylene ethane benzene Ill 8 80 x 10 1 10 days Ethene propane toluene IV 880 X 10quot2 2 24 h Propene 0 m and pxylene 124 and 125trimethylbenzene V 28 X 103911 lt2 h 2Methyl2butene d limonene Source Adapted from Damall er a1 1976 quot Units of cm3 molecule 1 5 1 note that k OH CH 4 has been revised downward Chapter 6 1 Half lives in atmosphere with respect to reaction with OH assuming OH 15 X 106 radicals cm 3 Recap Hydrocarbon Oxidation oxidation is fastest for alkenes double bond substitution speeds reaction aromatic hydrocarbons react similarly to alkenes oxidation is slower for alkanes increases with branching and chain length hundreds of possible intermediates and products all oxidations produce carbonyl species ozonealkene reactions are slow but become important at night other radical species than OH can oxidize HCs Recap Photochemical Ozone production A H02 NO gt OH N02 2 R02 NO gt R0 No2 N02hv 02M NO03M 00 9 OHN02M gtHN03M No2 R02 M gt ROONo2 PAN M 0 At low NOX ie R1R2 gtgt R4R5 PO3 z 1 Hoz39 k2 Roz39D NO At very high NOX ie R4R5 gt R1R2 PO3 1 I N02 P03 ppbhr PO dependence on N05 Z k VOC OHVOC NOX ppb Calculations by J Murphy UC Berkeley Ozone Smog development Concentration ppm Photolysis time min FIGURE 167 Typical primary and secondary pollutant pro les in a propeiieiNOVY irradiation in a smog chamber adapted from Pitts er al 1975 Ozone Smog develogment 400 A s Q I g O Hydrocarbons lt p Aldehydes E 0 Z 5 2 20 TIME OF DAY hour Figure 137 Evolution of the chemical composition of the lower atmosphere during a smog event Goody 1995 Ppm NOX Ozone isopleths HC N01 028 a 45 0 24 03ppm008 016 024 Kg 2 gt40 3 020 030 30 R 012 020 028 062 034 036 25 quotI 0 3 A 39 0 ll o16 Li gd g 20 ww 012 15 I I quotII Win i i 0 08 7 05 E B l 39 t n 0 c Q i a r39 03904 Limited 25 2 39 200 o I I I I I I I I 175 0 02 04 06 08 10 12 14 16 15 20 VOC pme 00 25 VOC Volatile Orgamc Compound pmeD FIGURE 1614 Typical peak ozone isopleths generated from initial mixtures of VOC and NOX in air a Twordimensional depiction generated from the EKMA model Dodge 1977a b threedimensional depi tion prepared by B Dickerson The VOClimited region eg at point D is found in some highly polluted urban centers while the NOX cg at point A is typical of downwind suburban and rural areas adapted from FinlaysonPitts and Pitts 1993 Ozone isopleths HC N01 100 300 Urban suburban 10 E 1 100 w h O 3 3 ppb r 5 Rural Q 3 1 3 10 Ox Z 3 3 i I Remote Remote I tropical Net 03 loss forest 71 3 03901 I lllllll I I I 1 1 10 100 1000 OH reactivity adjusted VOC ppr FIGURE 1638 Observed NOX and OHreactivity adjustcd VOC expressed as r pane in various regions of the troposphere Isupleths shown are midday rates of 03 production ppb h39l calculated using a box model adapted from Chameides et 1
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