3.10. Application of a reaction mechanism

There are several reaction mechanisms, which describe chemical transformation occurring in the atmosphere. These can differ from each other depending on what type of detailed description is needed. One of these mechanisms is the CBM Leeds (Table 3.1, Heard et al., 1998), which describe the photochemical air pollution formation in the troposphere. Elementary reactions in the mechanism are either thermal or photochemical reactions. We can construct a set of ordinary differential equations (ODEs) from a reaction mechanism, which describes the temporal variation of chemical species. These ODEs can be solved by various numerical methods with appropriate initial conditions. Figures 3.4–3.11 show the variation of different compounds involved in the mechanism in winter and summer.

Table 3.1: CBM Leeds mechanism

Reactions

Reaction rate coefficients ( k i )

   

NO2 + hν

NO+O

k1=1.45·10–2×exp(–0.4/ cosϕz)

(R1)

 

O + O2. M

O3

k2=1.4·103×exp(1175/ Tk)

(R2)

 

O3 + NO

NO2

k3=1.8·10–12×exp(–1370/ Tk)

(R3)

 

O + NO2

NO

k4=9.3×10–12

(R4)

 

O3 + NO2

NO3

k5=1.2·10–13×exp(–2450/ Tk)

(R5)

 

O3 + hν

O

k6=7.865·10–4×exp(–0.4/ cosϕz)

(R6)

 

O3 + hν

O1D

k7=2.0·10–4×exp(–1.4/ cosϕz)

(R7)

 

O1D (+M)

O

k8=1.9·108×exp(390/ Tk)

(R8)

 

O1D + H2O

OH + OH

k9=2.2·10–10

(R9)

 

O3+HO2

OH

k10=1.4·10–14×exp(–580/ Tk)

(R10)

 

NO3 + hν

0.89(NO2+O) + 0.11NO

k11=4.91·10–1×exp(–0.4/ cosϕz)

(R11)

 

NO3 + NO

NO2 + NO2

k12=1.3·10–11×exp(250/ Tk)

(R12)

 

NO3 + NO2 (+M)

N2O5

k13=5.3·10–13×exp(256/ Tk)

(R13)

 

N2O5 + H2O

HNO3 + HNO3

k14=1.3·10–21

(R14)

 

N2O5 + NO3

NO2

k15=3.5·1014×exp(–10897/ Tk)

(R15)

 

NO + NO

NO2 + NO2

k16=1.8·10–20×exp(530/ Tk)

(R16)

 

OH + NO (+M)

HONO

k17=4.5·10–13×exp(806/ Tk)

(R17)

 

HONO + hν

OH + NO

k18=2.86·10–3×exp(–0.4/ cosϕz)

(R18)

 

OH + NO2 (+M)

HNO3

k19=1.0·10–12×exp(713/ Tk)

(R19)

 

HO2 + NO

OH + NO2

k20=3.7·10–12×exp(240/ Tk)

(R20)

 

HO2 + HO2

H2O2

k21=5.9·10–14×exp(1150/ Tk)

(R21)

 

HO2 + HO2

+ H2O

H2O2

k22=2.2·10–38×exp(5800/ Tk)

(R22)

 

OH + CO

HO2

k23=2.2·10–13

(R23)

 

FORM + OH

HO2 + CO

k24=1.0·10–11

(R24)

 

FORM + hν

2 HO2 + CO

k25=5.40·10–5×exp(–0.79/ cosϕz)

(R25)

 

FORM + hν

CO

k26=6.65·10–5×exp(–0.6/ cosϕz)

(R26)

 

ALD2 + OH

C2O3

k27=7.0·10–12

(R27)

 

ALD2 + hν

MEO2 + HO2 + CO

k28=1.35·10–5×exp(–0.94/ cosϕz)

(R28)

 

C2O3 + NO

NO2 + MEO2

k29=5.4·10–12×exp(250/ Tk)

(R29)

 

C2O3 + NO2

PAN

k30=8.0·10–20×exp(5500/ Tk)

(R30)

 

PAN

C2O3 + NO2

k31=9.4·1016×exp(–14000/ Tk)

(R31)

 

MEO2 + NO

FORM + HO2 + NO2

k32=4.2·10–12×exp(180/ Tk)

(R32)

 

MEO2 + C2O3

MEO2 + FORM + HO2

k33=3.0·10–12

(R33)

 

C2O3 + C2O3

2 MEO2

k34=2.5·10–12

(R34)

 

MEO2 + HO2

0.77(FORM + HO2 + OH)

k35=7.5·10–14×exp(1300/ Tk)

(R35)

 

C2O3 + HO2

0.79(MEO2 + OH)

k36=6.5·10–12

(R36)

 

OH

MEO2

k37=1.1·102×exp(–1710/ Tk)

(R37)

 

PAR + OH

–NO + 0.87 NO2 + 0.77 ROR + 0.1(HO2 + ALD2)

k38=8.1·10–13

(R38)

 

ROR

1.1 ALD2 + 0.94 NO2 + 0.96 HO2 + 0.2(KET-NO-PAR) + 0.02 ROR

k39=1.05·1015×exp(–8000/ Tk)

(R39)

 

ROR

KET + HO2

k40=1.6·103

(R40)

 

KET + hν

C2O3 + 0.95(NO2 + HO2 + ALD2)-NO

k41=4.35·10–6×exp(–0.4/ cosϕz)

(R41)

 

OH + OLE

MEO2 + ALD2

k42=5.2·10–12×exp(504/ Tk)

(R42)

 

O3 + OLE

0.5 ALD2 + 0.52 FORM

+ 0.12 CO + 0.17 HO2 + 0.22 MEO2 + 0.1 OH

k43=1.4·10–14×exp(–2105/ Tk)

(R43)

 

OH + ETH

–NO + NO2 + 1.56 FORM

+HO2 + 0.22 ALD2

k44=2.0·10–12×exp(411/ Tk)

(R44)

 

O3 + ETH

FORM

k45=1.25·10–14×exp(–2633/ Tk)

(R45)

 

OH + TOL

0.08(–NO + NO2)

+ 0.36 CRES + 0.44 HO2

+ 0.56 TO2

k46=2.13·10–12×exp(322/ Tk)

(R46)

 

TO2 + NO

0.9(NO2 + OPEN+ HO2)

k47=8.1·10–12

(R47)

 

TO2

HO2 + CRES

k48=4.2

(R48)

 

OH + CRES

0.22 NO2 + 0.61 NO

+ 0.3 OPEN

k49=4.1·10–11

(R49)

 

NO3 + CRES

–NO2

k50=2.2·10–11

(R50)

 

OH + XYL

0.7 HO2 + 0.5 (–NO + NO2) + 0.2 CRES

+ 0.8 MGLY

+ 1.1 PAR + 0.3 TO2

k51=1.66·10–11×exp(116/ Tk)

(R51)

 

OH + OPEN

–NO + NO2 + C2O3

+ 2(HO2 + CO) + FORM

k52=3.0–11

(R52)

 

OPEN + hν

C2O3 + CO + HO2

k53=4.88·10–4×exp(–0.79/ cosϕz)

(R53)

 

O3 + OPEN

0.03 (–NO + NO2 + ALD2)

+ 0.62 C2O3 + 0.7(FORM + CO) + 0.08 OH +

+ 0.75 HO2 + 0.2 MGLY

k54=5.43·10–17×exp(–500/ Tk)

(R54)

 

OH + MGLY

NO + NO2 + C2O3

k55=1.7·10–11

(R55)

 

MGLY + hν

C2O3 + CO + HO2

k56=5.2·10–4×exp(–0.79/ cosϕz)

(R56)

 

O + ISOP

0.49 HO2 + 0.44 ALD2

+ 0.6 OLE + 0.25(–NO

+ NO2 + CO) + 0.15 KET

+ 0.45 PAR + 0.05(MEO2

+ C2O3)

K57=1.82·10–11

(R57)

 

OH + ISOP

–NO + 0.87 (NO2 + HO2)

+ FORM + OLE)

+ 0.58 (KET + PAR)

+ 0.29 ALD2

k58=9.6·10–11

(R58)

 

O3 + ISOP

FORM + 0.45 ALD2

+ 0.65 OLE + 0.35 CO

+ 0.2(PAR+KET)

k59=1.2·10–17

(R59)

 

Diurnal variation of ozone concentration in summer and winter time

Figure 3.4: Results of the numerical simulations using CBM Leeds mechanism – variation of ozone in summer and winter time

Diurnal variation of OH radical concentration in summer and winter time

Figure 3.5: Results of the numerical simulations using CBM Leeds mechanism – variation of OH radical in summer and winter time

Diurnal variation of HO2 radical concentration in summer and winter time.

Figure 3.6: Results of the numerical simulations using CBM Leeds mechanism – variation of HO2 radical in summer and winter time.

Diurnal variation of TO2 species concentration in summer and winter time.

Figure 3.7: Results of the numerical simulations using CBM Leeds mechanism – variation of TO2 species in summer and winter time.

Diurnal variation of NOx concentration in summer.

Figure 3.8: Results of the numerical simulations using CBM Leeds mechanism – variation of NOx in summer time.

Diurnal variation of NOx concentration in winter.

Figure 3.9: Results of the numerical simulations using CBM Leeds mechanism – variation of NOx in winter time.

Diurnal variation of TOL species concentration in summer and winter time.

Figure 3.10: Results of the numerical simulations using CBM Leeds mechanism – variation of TOL (toluene) species in summer and winter time.

Diurnal variation of XYL species concentration in summer and winter time.

Figure 3.11: Results of the numerical simulations using CBM Leeds mechanism – variation of XYL (xylol) species in summer and winter time.

References

Atkins P.W., de Paula J., and Atkins P.. 1997. Physical Chemistry. Macmillan Higher Education.

Heard A.C., Pilling M.J., and Tomlin A.S.. 1998. Mechanism reduction techniques applied to tropospheric chemistry In: Atmospheric Environment. 32. 1059-1073.

Jacob, D.J.. 1999. Introduction to Atmospheric Chemistry. Princeton University Press.

Mészáros E.. 1977. The Basics of Atmospheric Chemistry, (In Hungarian). Akadémiai Kiadó.

Pilling M.J. and Seakin P.W.. 1995. Reaction Kinetics (Oxford Science Publications). Oxford University Press, USA.

Seinfeld J.H. and Pandis S.N.. 2006. Atmospheric Chemistry and Physics: From Air Pollution to Climate Change. Wiley.

Turányi T.. 2010. Investigation of reaction mechanisms (In Hungarian). Akadémiai Kiadó.