Nitrogen dioxide hydroxyl radical reaction

Similarly, recent experiments" have been interpreted to mean that about 10% of the reaction of hydroperoxy radical with nitric oxide gives per-nitrous add, HOONO, instead of nitrogen dioxide and hydroxyl radical. Because this reaction is of major importance, even 10% of a second channel would be important, although it has been argued that such compounds would not be sufFidently stable to accumulate in the atmosphere." Whether such peroxynitrogen compounds are stable in the gas phase and whether they can be found in the atmosphere must await further experiments. 

The quantum yield of reaction 17 varies with the irradiation wavelength, from about 0.07 near 300 nm to 0.025 at 355 nm down to 0.015 at 371 nm [35,40]. Differently from nitrate, nitrite is a source but also a sink for the hydroxyl radical, the latter reaction yielding nitrogen dioxide [35,37-40,43] ... 

Reactions 2-6 through 2-8 form a catalytic cycle, in that the hydroxyl radical that is used in Reaction 2-6 is r enerated in Reaction 2-8. The net results of this cycle are the oxidations of nitric oxide to nitrogen dioxide and carbon monoxide to carbon dioxide by the oxygen present in the air. 

FIGURE 3 12 Possible initial steps for ozone, atomic oxygen, nitrogen dioxide, and hydroxyl-radical reaction with aromatic hydrocarbons. 

FIGURE 3-13 Relations between conversion of nitric oxide to nitrogen dioxide and ozone, atomic oxygen, and hydroxyl-radical reaction rate constants. Reprinted with permission from Grosjean. ... 

Chemical radicals—such as hydroxyl, peroxyhydroxyl, and various alkyl and aryl species—have either been observed in laboratory studies or have been postulated as photochemical reaction intermediates. Atmospheric photochemical reactions also result in the formation of finely divided suspended particles (secondary aerosols), which create atmospheric haze. Their chemical content is enriched with sulfates (from sulfur dioxide), nitrates (from nitrogen dioxide, nitric oxide, and peroxyacylnitrates), ammonium (from ammonia), chloride (from sea salt), water, and oxygenated, sulfiirated, and nitrated organic compounds (from chemical combination of ozone and oxygen with hydrocarbon, sulfur oxide, and nitrogen oxide fragments). ... 

Dransfield, T. J., K. K. Perkins, N. M. Donahue, J. G. Anderson, M. M. Sprengnether, and K. L. Demerjian, Temperature and Pressure Dependent Kinetics of the Gas-Phase Reaction of the Hydroxyl Radical with Nitrogen Dioxide, Geophys. Res. Lett., 26, 687-690 (f999). 

Fig. 7.3 Reactions showing the generation of ROS during lipid peroxidation and oxidative stress. Hydroxyl radical ( OH) lipid radical ( lipid), peroxyl radical (lipid-OO ) lipid peroxide (lipid-OOH) nitric oxide ( NO) nitrogen dioxide (N02) peroxynitrite anion (ONOO-) hypochlorous acid (HOC1), and hydrogen peroxide (H202)...

As Barr et al. (2003) pointed out, the importance of such emissions is determined mainly by their impact on the three processes taking place in the atmosphere. The first consists in that such NMHCs as isoprene form in the course of carboxylization in plants and contribute much thereby to the formation of biospheric carbon cycle. The second process is connected with NMHCs exhibiting high chemical activity with respect to such main oxidants as hydroxyl radicals (OH), ozone (03), and nitrate radicals (N03). Reactions with the participation of such components result in the formation of radicals of alkylperoxides (R02), which favor efficient transformation of nitrogen monoxide (NO) into nitrogen dioxide (N02), which favors an increase of ozone concentration in the ABL. Finally, NMHC oxidation leads to the formation of such carbonyl compounds as formaldehyde (HCHO), which stimulates the processes of 03 formation. Finally, the oxidation of monoterpenes and sesquiterpenes results in the intensive formation of fine carbon aerosol with a particle diameter of <0.4 pm... 

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