OH radical reaction with

P igure 43 shows an Arrhenius plot for reaction (xv), and leads to 

This expression gives preference to the lower value of fe, 5 at 773 K, and as a result it predicts lower values than the recommendation of Baulch et al. [55] at higher temperatures. Equation (86) agrees closely with the expression fei 5 = (4.8 1.0) x 10 exp —(670 70)/T) recently given by Hack et al. [281]. 

sec at 773 K. It should perhaps be re-emphasized here that the values of 7 in Table 18 were optimized assuming no contribution from the possible alternative step 

Equation (87) confirms that the activation energy E, 0 is small. 

Both expressions (85) and (88) rely heavily on the work of Albers et al. [74] for their temperature dependence. The value of E,, = 18.6 kcal. mole is some 3—4 kcal. mole lower than would be expected from the values of fe,, /fel ) obtained by Baldwin et al. [72] over the smaller temperature range from 743—803 K. 

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Sinks, chemical species, or method OH, reaction with OH radical S, sedimentation P, precipitation scavenging NO, reaction with NO radical uv, photolysis by ultraviolet radiation Sr, destmction at surfaces O, adsorption or destmction at oceanic surface. 

Aldehydes undergo two primary reactions photolysis and reaction with OH radicals. These reactions lead to formation of CO, H, and R radicals. 

In the case of ACSO it was found also that N20 addition reduces the yield of S-allyl-L-cysteine (ACS), indicating that this product is formed by eaq - but not by OH radicals. As a result it can be expected that KBr addition will not reduce the ACS yield. It was found that KBr not only does not reduce the yield of ACS, but it rather increases i ts formation. This is explained as due to ACS formation by reaction of eaq" with ACSO, and its disappearance by reaction with OH radicals to give back ACSO as it is known for the reaction with sulfides. The authors suggest the same reactions for PCSO and PCS (propyl-L-cysteine) although the yield of PCS was not determined. 

Clearly, whether or not ozone is formed depends also on the rate at which, for example, unsaturated hydrocarbons react with it. Rates of reactions of ozone with alkanes are, as noted above, much slower than for reaction with OH radicals, and reactions with ozone are of the greatest significance with unsaturated aliphatic compounds. The pathways plausibly follow those involved in chemical ozonization (Hudlicky 1990). 

In humid air, oxidation of NO, by reactions with OH radicals produced by dissociation of water molecules may occur as well, leading to the formation of HN02 and HN03 [77,79] ... 

Of the major components of flue gas, oxygen and water vapor influence the reactions of the oxides considerably, hut carbon dioxide does not. Under irradiation, NO is oxidized by reactions with O, OH, and H02 radicals. The resultant N02 is oxidized to HN03 by reaction with OH radicals. S02 is similarly oxidized to H2S04 by reactions with O and OH. The products can also be converted to aerosols and collected in electrostatic precipitators. 

Extensive research has been conducted into the atmospheric chemistry of organic chemicals because of air quality concerns. Recently, Atkinson and coworkers (1984, 1985, 1987, 1988, 1989, 1990, 1991), Altshuller (1980, 1991) and Sabljic and Glisten (1990) have reviewed the photochemistry of many organic chemicals of environmental interest for their gas phase reactions with hydroxyl radicals (OH), ozone (03) and nitrate radicals (N03) and have provided detailed information on reaction rate constants and experimental conditions, which allowed the estimation of atmospheric lifetimes. Klopffer (1991) has estimated the atmospheric lifetimes for the reaction with OH radicals to range from 1 hour to 130 years, based on these reaction rate constants and an assumed constant concentration of OH... 

Oxidation rate constant k, for gas-phase second order rate constants, koH for reaction with OH radical, kN03 with N03 radical and ko3 with 03 or as indicated, data at other temperatures and/or the Arrhenius expression see reference ... 

Oxidation rate constant k, for gas-phase second order rate constants, k0H for reaction with OH radical, kNQ3 with N03 radical and k03 with 03 or as indicated data at other temperatures see reference k0(3P) = 5.8 x lO14 cm3 molecule-1 s-1 for the reaction with 0(3P) (Herron Huie 1973) koe = (3.74 0.13) x 10-12 cm3 molecule-1 s-1 at 300 K (relative rate method, Darnall et al. 1978) kOH = 5.0 x 10-12 cm3 molecule-1 s-1 (Atkinson et al. 1979)... 

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