Photolysis indirect

The methyl parathion released to the atmosphere can be transported back to surface water and soil by wet deposition. Methyl parathion that is released to the atmosphere can also be transformed by indirect photolysis to its oxygen analog, methyl paraoxon, by oxidation with photochemically produced oxygen radicals. However, methyl parathion is not expected to undergo significant transformation to methyl paraoxon. 

Diisopropyl methylphosphonate does not undergo direct or indirect photolysis in aquatic systems, as demonstrated by the stability of the compound in distilled water or in a natural water sample after 232 hours of reaction time with the mercury lamp filtered to exclude all wavelengths below 290 nm (Spanggord et al. 1979). 

Calculations showed that this indirect photolysis occurs between 2.5 and 4 times faster than the processes occurring in the upper atmosphere. Analogous reactions were described by Clarke and Ferris (1997) ... 

SCHEME II - Direct and Indirect Photolysis of MDI Based Polyurethanes... 

Hebert VR, Miller GC. 1990. Depth dependence of direct and indirect photolysis on soil surfaces Agric Food Chem 38 913-918. 

Photolytic. Under smog conditions, indirect photolysis via OH radicals yielded phosgene, di-chloroacetyl chloride, and formyl chloride (Howard, 1990). These compounds are readily hydrolyzed to HCl, carbon monoxide, carbon dioxide, and dichloroacetic acid (Morrison and Boyd, 1971). Dichloroacetic acid and hydrogen chloride were reported to be aqueous photodecomposition products (Dilling et al., 1975). Reported rate constants for the reaction of trichloroethylene and OH radicals in the atmosphere 1.2 x 10 cm /molecule-sec at 300 K... 

Pereira VJ, Weinberg HS, Linden KG, Singer PC (2007) UV degradation kinetics and modeling of pharmaceutical compounds in laboratory grade and surface water via direct and indirect photolysis at 254 nm. Environ Sci Technol 41 1682-1688... 

What is the difference between direct and indirect photolysis ... 

Indirect Photolysis Reactions with Photooxidants in Natural Waters and in the Atmosphere... 

Illustrative Example 16.2 Estimating the Indirect Photolysis Half-Life of Atrazine in a Shallow Pond Reactions with Singlet Oxygen ( 02)... 

Indirect Photolysis in the Atmosphere (Troposphere)—Reactions with Hydroxyl Radical (HO )... 

Figure 16.2 Pathways for indirect photolysis of an organic compound i involving excited natural organic matter constituents. UC refers to unknown chromophores. Wavy arrows symbolize radiationless transition (adapted from Zafiriou et al., 1984).

For describing the kinetics of indirect photolysis of organic pollutants involving well-defined photooxidants (e.g., HO , 02, CO] ), we adapt the approach suggested by Hoigne et al. (1989) and Mill (1989). The rate of formation, rf ox(A), of a given photooxidant (Ox) by radiation of wavelength A may be described by ... 

Now we have an easy way of describing the indirect photolysis of a pollutant by a pseudo-first-order rate law, provided that the compound considered does not significantly affect [Ox]°, and that we are able to measure or estimate [Ox]°. The nearsurface rate of loss of the pollutant is then given by ... 

The indirect photolysis half-life of atrazine (assuming that reaction with HO is the dominant process) is then given by (Eq. 16-7) ... 

The right-hand scale in Fig. 16.5 gives the calculated half-lives for indirect photolysis involving 02 for the various compounds in the well-mixed epilimnion of... 

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