1. Site description and equipment
A dependence of the ozone formation rate on the surface air temperature
B.D. Belan, D.E. Savkin, G.N. Tolmachev
V.E. Zuev Institute of Atmospheric Optics SB RAS, , Russia, Tomsk, sq. Akad. Zueva, 1 )
Introduction
Studying the formation and dynamics of ozone in the atmosphere is important for several reasons. First, the contribution of tropospheric ozone to the global greenhouse effect is only slightly less than that of water vapor, carbon dioxide, and methane. Second, tropospheric ozone is a strong poison that has negative effects on human health, animals, and vegetation. Third, as a potent oxidizer, ozone destroys almost all materials, including platinum group metals and compounds. Fourth, ozone is formed from precursor gases as a result of photochemical processes, but not discharged into the atmosphere by any industrial enterprises or as a result of other processes. Therefore, one must know the mechanisms of its emergence.
Discussion
Empirical equation of the photochemical formation of ozone
where f is the stoichiometric coefficient of hydrocarbon transformation; K is the ozone production coefficient depending on the concentrations of nitrogen oxides that switch its generation chains; and Р denotes the products of photochemical reactions, that is, aerosol particles emerging at the interaction of gas constituents.
The physical meaning of the empirical equation is clear: primary substances (carbon oxide (СО), methane (СН4), non-methane hydrocarbons (RH), nitrogen oxide (NO)) get into a real atmosphere with water vapor (Н2О) and oxygen (О2). Under the action of ultraviolet radiation (h), they are transformed into more toxic compounds: formaldehyde (Н2СО), ozone (О3), nitrogen dioxide (NO2), and reaction products (Р), usually in the form of aerosols
Aim
Many authors analyzing dynamics of surface ozone concentration note that its concentration depends on some meteorological quantities, in particular, on air temperature. However, the form of this relation has not yet been determined. The main aim of the present work is to determine the nature of this relationship.
Photolysis rate versus
air temperature
Emission rate of terpenes versus air temperature
Site description and equipment
Data from a TOR-station (56°28'41'‘ N, 85°03'15'' E) are used for analysis. This is an automatic station located in the north-eastern outskirts of the Academic City (Akademgorodok) of Tomsk in the building of a high-altitude atmospheric sounding station at the V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Sciences (IAO SB RAS). There are no industrial objects or motorways near the station, and the effects of local gas and aerosol sources are decreased. The station is located in the zone of boreal forests and surrounded by small deciduous and coniferous forest stands.
Fig. 5. Terpene emission rate by pine needles versus air temperature.
Fig. 4. Photolysis rate versus air temperature.
The fig. 4 , which is based on data from Matsumi et al., 20021, shows photolysis rate versus air temperature in relative units.
Photochemical formation of ozone starts from the photolysis of tropospheric ozone. In some papers, it is observed that the photolysis rate depends on the air temperature.
In this figure shows an example of generation of terpenes by pine needles versus air temperature. The curve is constructed with tabulated data from Isidorov,
It follows from that there exists a nonlinear positive relationship between the increasing rate of terpene emission by pines and air temperature.
JSC OPTEC 3.02 P-A
Ozone analyzer
TEI model 49c
1-500 µg/m3
Measure range
Low 0-0,2 ppm
High 0-0,5 ppm
±20%
Accuracy
± 0,5% of F. S. (Full scale)
Russia
Place of Origin
USA
Chemiluminescence
Method UV
Reaction rates of photochemical ozone generation cycles at various
temperatures №
Reactions
Constants 1
O+O2+M→O3+M
6.0*10-34(T/300)-2.6 2
H+O2+M→HO2+M
5.4*10-32(T/300)-1.8 3
O+HO2→HO+O2
2.7*10-11exp (224/T) 4
O+H2O2→HO+HO2
1.4*10-12 exp(-2000/T) 5
HO+HO+M→H2O2+M
6.9*10-31(T/300)-0.8 6
O+NO+M→NO2+M
1.0*10-31(T/300)-1.6 7
O+NO2→O2+NO
5.5*10-12 exp (188/T) 8
HO+CH4→H2O+CH3
1.85*10-12 exp (-1690/T) 9
HO+C2H4 +M→C2H4OH+M
8.6*10-29 (T/300) -3.4 10
HO+C2H6→H2O+C2H5
6.9*10-12 exp (-1000/T) 11
HO+C3H6+M→C3H6OH+M
8.0*10-27 (T/300) -3.5 12
HO+C3H8→H2O+C3H7
7.6*10-12 exp (-585/T) 13
HO+α-pinene→products
1.2*10-11 exp (440/T) 14
HO+CO→H+CO2
9.1*10-19*T1.77 exp (580/T) 15
NO3+C2H4→ products
3.3*10-12 exp (-2880/T) 16
NO3+C3H6→products
4.6*10-13 exp (-1155/T) 17
NO3+n-C4H10→products
2.8*10-12 exp (-3280/T) 18
NO3+ α-pinene→products
1.2*10-12 exp (490/T)
Method
In anticyclonic conditions are observed prolonged periods (several days) , when the temperature decreases or increases , and this process is accompanied by a decrease or an increase in the surface ozone concentration . ΔT ΔT
ΔO3
ΔO3
Fig. 6. Reaction rates of ozone cycles at various temperatures.
Were chosen , from an available database (Atkinson et al., 2004)*, the reactions that are most typical for photochemical ozone generation cycles. This slide shows reaction rates calculated by formulas for a temperature range in the real atmosphere from -50 °С to +50 °С. To compare the constants at various temperatures, they are normalized to the values at the minimal temperature. The calculations have shown that as the temperature increases, the reaction rates can either increase or decrease. The fig.6 presents the reactions whose rates decrease with increasing temperature, and the figure on the the right, the reactions whose rates increase with increasing temperature.
Fig. 1. Air temperature (Т) and near-surface ozone concentration (O3) in the city of Tomsk: a) heat wave, b) cold wave.
Reaction rates of sink of ozone from the atmosphere at various temperatures
Some earlier investigations have shown that there may be a several fold change even in the annual average concentration of ozone in the Tomsk region. Therefore, in the present work only data for some four years denoted by circles in this figure have been processed.
absolute maximum №
Reactions
Constants 1
O3+C2H4→ products
9.1*10-15 exp (-2580/T) 2
O3+C3H6→ products
5.5*10-15 exp (-1880/T) 3
O3+ α-pinene→products
6.3*10-16exp (-580/T) 4
O3+NO→NO2+O2
1.4*10-12 exp(-1310/T) 5
O3+NO2→NO3+O2
1.4*10-13 exp(-2470/T)
intermediate values
absolute minimum
In addition to the formation of ozone during the photochemical reactions, there is sink of ozone (both during other reactions and under interaction with gases and aerosols of the air). The reactions of sink of ozone from the atmosphere are presented in the table on the left. The results of calculations by the above formulas for the constants are given in figure on the right. The data are normalized to the constant value at the minimal temperature.
Fig. 2. Ozone concentration variation in the Tomsk region in
Fig. 7 Rates of ozone reactions with gas constituents at various temperatures.
Results
Conclusions
The above investigation has shown that there is a nonlinear relationship between ozone formation in the atmosphere and air temperature. This relationship varies considerably from year to year, and is due to a nonlinear increase in the concentration of organic gases with increasing air temperature and increasing reaction rates for some of the gases – ozone precursors.
Main conclusions:
First, in all years considered the rate of ozone formation changes nonlinearly with air temperature, and can be best described by a second-order exponent
Second, ozone formation varies considerably with temperature from year to year
Third, ozone generation changes with temperature from -40 оС to 0 оС almost linearly. Nonlinear (almost quadratic) rise starts at positive temperatures. The process activates at an air temperature >10 оС
Acknowledgements
This work was supported by the Ministry of Education and Science contract no (ID: RFMEFI61314X0013).
Reference
1. Matsumi Y., Comes F. J., Hancock G., Hofzumahaus A., Hynes A. J., Kawasaki M., Ravishankara A. R., Quantum yields for production of O(1D) in the ultraviolet photolysis of ozone: Recommendation based on evaluation of laboratory data. J. Geophys. Res.107, 4024, DOI: /2001JD000510
2. Isidorov V.A., Volatile emissions of plants: composition, emission rate, and ecological role. Saint-Petersburg: Alga, 188
3. Atkinson R., Baulch. D.L., Cok R.A., Crowley J.N., Hampson R.F., Hynes R.G., Jenkin M.E., Rossi M.J., Troe J., Evaluated kinetic and photochemical data for atmospheric chemistry; Volume 1 – gas phase reactions of Ox, HOx, NOx and SOx species. Atmos. Chem. Phys. 4, pp
Figure 3. Ozone generation versus air temperature.