The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical...

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The Atmosphere as a Chemical Reactor Outputs Input s Chemistry Radiation (energy) Biogeochemical Cycling

Transcript of The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical...

Page 1: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

The Atmosphere as aChemical Reactor

OutputsInputs

Chemistry

Radiation (energy)

Biogeochemical Cycling

Page 2: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Temperature Structure of the Atmosphere

from: http://www.uwsp.edu/geo/faculty/ritter/images/atmosphere/structure_composition/atmospheric_structure.jpg

Page 3: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Pressure Structure of the Atmosphere

from: http://okfirst.ocs.ou.edu/train/meteorology/graphics/VertTP.gif

H

Z

oePP

km4.7Mg

RT H

Page 4: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Mixing Ratio vs. Concentration• Mixing Ratio – the fraction of air by volume that

is composed of a certain compound.– The fraction of N2 is 0.80 or 80%– The fraction of N2O is 3.6x10-7 or 3.6x10-5% or 360

ppbv.

• Concentration (number density) – number of molecules of a specified compound contained in a fixed volume.– [N2O] at 1010 mbar = 8.86x1012 molecules/cm3

– [N2O] at 500 mbar = 4.38x1012 molecules/cm3

The atmosphere has a density of

2.69x1019 molecules/cm3 at sea level

Page 5: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Chemical Composition of the Atmosphere

Compound Mixing Ratio

N2 0.78

O2 0.21

Ar 0.0093

CO2 3.6x10-4

Ne 8x10-6

He 5.2x10-6

CH4 1.7x10-6

Kr 1.1x10-6

H2 5.0x10-7

N2O 3.6x10-7

Xe 9.0x10-8

O3 1 – 10x10-8

H2O

Page 6: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Vertical Mixing of the Troposphere

• Boundary Layer – hours to days

• Free Troposphere – days to weeks

• Tropopause - years

Page 7: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Horizontal Mixing of the Troposphere

from: Jacob

Page 8: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Horizontal Mixing of the Troposphere

Page 9: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Kinetics

B A AB 1k

[AB]k[AB][B][A]

1

dt

d

dt

d

dt

d

D C B A 2k

[A][B]k[D][C][B][A]

2

dt

d

dt

d

dt

d

dt

d

Page 10: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Kinetics

22k

24 CO O2H 2O CH

224

4 ]][Ok[CH][CH

dt

d

Only true for elementary reactions!

Page 11: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Lifetime, Pseudo First Order • First order reaction:

• Second order reaction:

1k

1 AB])([

B][k

1

k

1 A])([

2

D C B A 2k

B A AB 1k

B][kk where[A];k[A][B]k[A]

22 dt

d

Page 12: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Lifetime• Some compounds have multiple sinks

• Methane

chemical loss in troposphere by OH ≈ 12yrs

physical deposition to the soil ≈ 100 yrs

chemical loss in stratosphere ≈ 40 yrs

Overall lifetime: 40

1

100

1

12

11111

stratsoilOHtot

yrs5.8tot

Page 13: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Rate ConstantsEffect of Temperature on Rate Constant

1.0E-16

1.1E-15

2.1E-15

3.1E-15

4.1E-15

5.1E-15

6.1E-15

7.1E-15

200 220 240 260 280 300

Temperature (Kelvin)

k (c

m3/

mo

lecu

les

s)

RT

Ea

A k

e

Page 14: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

J Values

• Photochemistry

320nm D);O( O O 12

j3 h

][O][O

33 j

dt

d

max

min

)()()( o

dj

Page 15: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Radical Chemistry

• Radicals do the work of the chemistry in the atmosphere.

• Produced by photochemical reactions and reactions by other radicals

• O(3P) is a bi-radical

• O(1D) is not a radical, but it is very reactive

Page 16: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

The OH Radical

OH2OHD)O(

320nm D);O( O O2

1

k2

1

12

j3

h

M P)O(MD)O( 3k1 3

Page 17: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Production of OH Radical

O]D)][H[O(k2[OH]

21

2dt

d

Assume steady-state for O(1D)

D)][M][O(kO]D)][H[O(k]O[ 132

123 j

Production Loss

Page 18: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Production of OH RadicalSolve for [O(1D)]

[M]kO][Hk

]O[D)][O(

322

31

j

Substitute into the production of OH

M][kO]H[k

O]][H[Ok2[OH]

322

2321

j

dt

d

Page 19: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Oxidation of CO

MOMO O

ONOhNO

OHNONOHO

MHOMO H

HCOOH CO

32

2

22

22

2

32h

2 OCO2O CO :reactionnet

Page 20: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

The Chemical Family NOx

22k

3

3k

2

J2

ONONOO

MOMOO

ONOh NO

2

1

1

3h

2 ONONO

Page 21: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

The Chemical Family NOx

NO][k

][NOj]O[

]O[k

j

][NO

[NO]

0[NO]

NO]][O[k-][NOj[NO]

2

213

32

1

2

3221

dt

d

dt

d

Page 22: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Coupling of NOx and HOx

3h

2 ONO NO

2HO OHCO

NOslow

fast

Page 23: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Sinks for NOx and HOx

OHROHRH

rainoutOOHHOHO

rainoutHNO NOOH

2

22222

32

2222

22

HOOHOHOH

2OHhOH

Page 24: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

O3 Production

formed O No ONONOO

OOHHOHO :NO Low

production O OHNONOHO :NOHigh

3223

22222x

322x

Page 25: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Oxidation of Formaldehyde

COHOOHCO

OHHCO OHHCHO

COH

HCOH hHCHO

22

2

2

Maximum O3 production = 3 molecules (high NOx)Maximum HOx production = 2 molecules (high NOx)

Minimum O3 production = 0 molecules (low NOx)Minimum HOx producion = -2 molecules (low NOx)

Page 26: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

Oxidation of Methane

2223

33

2233

223

23223

2323

2323

234

HOOCHOOCH

OH OCHhOOHCH

OHOCHOHOOHCH

OHOH OCHOHOOHCH

OOOHCHHOOCH

NOOCHNOOCH

MOCHMOCH

OHCH OHCH

Can oxidize NOto NO2 just like HO2

formaldehyde

Page 27: The Atmosphere as a Chemical Reactor OutputsInputs Chemistry Radiation (energy) Biogeochemical Cycling.

O3 Production by Methane

• High NOx (maximum O3 and HOx production):

• Low NOx (minimum O3and HOx production):

2OH5OOHCO O10CH 32224

22224 HOOH3CO 2OOH3CH