Sunlight rate constants

Direct photolysis sunlight rate constant in water bodies in the environment = kAE, the maximum direct photolysis sunlight rate constant in water bodies in the environment... 

This new analytical method determines the rate constant and activation energy of Kevlar s photooxidative processes. The 0.2 atm of oxygen-18-labelled environment in a solar chamber simulates the air-exposure under sunlight conditions. The technique also allows the radial 0-distribution measurement from the fiber surface toward the fiber center. The data from the accelerated experimental conditions in the solar chamber in an 02-atmosphere are differentiated from the usual daylight exposure effects. 

Photolysis photodegradation of 5 ppm initial concentration in methanol-water (3 7, v/v) by high pressure mercury lamp or sunlight with a rate constant k = 1.84 x 1CL3 mur1 and t, 2 = 6.27 h (Wang et al. 1991) the... 

Volatilization removal rate constants from the water column at 25°C in midsummer sunlight were k = 0.002 Ir1 in deep, slow, somewhat turbid water k = 0.001 Ir1 in deep, slow muddy water k = 0.002 h 1 in deep slow, clear water k = 0.042 Ir1 in shallow, fast, clear water and k = 0.179 h 1 in very shallow, fast, clear water (Southworth 1977) aquatic tA = 18-300 h (Callahan et al. 1979) ... 

Photolysis direct photochemical transformation t,/2(calc) = 21 h, computed near-surface water, latitude 40°N, midday, midsummer and photolysis t,/2 = 160 d and 200 d in 5-m deep inland water body without and with sediment-water partitioning, respectively, to top cm of bottom sediment over full summer day, 40°N (Zepp Schlotzhauer 1979) t,/2 = 21 h, atmospheric and aqueous photolysis half life, based on measured sunlight photolysis rate constant in water adjusted for midday summer sunlight at 40°N latitude and t,/2 = 63 h after adjusting for approximate winter sunlight intensity (Howard et al. 1991) t,/2 = 160 d under summer sunlight in surface water (Mill Mabey 1985) ... 

Behymer and Hites (1985) determined the effect of different substrates on the rate of photooxidation of anthracene (25 pg/g substrate) using a rotary photoreactor. The photolytic half-lives of anthracene using silica gel, alumina, and fly ash were 1.9, 0.5, and 48 h, respectively. Anthracene (5 mg/L) in a methanol-water solution (1 1 v/v) was subjected to a high pressure mercury lamp or sunlight. Based on a rate constant of 2.3 x lO /min, the corresponding half-life is 30 min (Wang et al., 1991). 

Photolytic. Synthetic air containing gaseous nitrous acid and exposed to artificial sunlight (A, = 300-450 nm) photooxidized 2-butanone into peroxyacetyl nitrate and methyl nitrate (Cox et al., 1980). They reported a rate constant of 2.6 x 10 cm /molecule-sec for the reaction of gaseous 2-butane with OH radicals based on a value of 8 x 10 cm /molecule-sec for the reaction of ethylene with OH radicals. 

Chrysene (5.0 mg/L) in a methanol-water solution (1 1 v/v) was subjected to a high pressure mercury lamp or sunlight. Based on a rate constant of 7.07 x 10 Vmin, the corresponding half-life is 1.63 h (Wang et al, 1991). 

Photolytic. The following rate constants were reported for the reaction of hexane and OH radicals in the atmosphere 7.15 x lO cmVmolecule-sec (Atkinson, 1990). Photooxidation reaction rate constants of 7.19 x lO and 1.36 x 10 cmVmolecule-sec were reported for the reaction of heptane with OH and NO3, respectively (Sabljic and Giisten, 1990). Based on a photooxidation rate constant 7.15 x lO cmVmolecule-sec for heptane and OH radicals, the estimated atmospheric lifetime is 19 h in summer sunlight (Altshuller, 1991). 

Photolytic. Based on a photooxidation rate constant of 8.90 x 10 cm /molecule-sec for the reaction of 3-methylheptane and OH radicals, the estimated lifetime is 16 h during summer sunlight (Altshuller, 1991). 

TCDD in a water-acetonitrile mixture (90 10) was exposed to summer sunlight. Based on the measured rate constant for this reaction, the estimated half-life is 27 h (Dulin et al., 1986). 

Decabromodiphenyl ether (BDE-209) is a major industrial product from the polybrominated diphenyl ethers used as flame retardants derivatives of this product have been detected in the environment. After exposure to the land surface, these contaminants adsorb on soil materials and may reach the atmosphere as particulate matter these particulates are subsequently subject to photolytic reactions. In this context, Ahn et al. (2006) studied photolysis of BDE-209 adsorbed on clay minerals, metal oxides, and sediments, under sunhght and UV dark irradiation. Dark and light control treatments during UV and sunlight irradiation showed no disappearance of BDE-209 during the experiments. Data on half-lives and rate constants of BDE-209 adsorbed on subsurface minerals and sediments, as determined by Ahn et al. (2006) and extracted from the literature, are shown in Table 16.6. 

The photooxidation of fuel oil no. 2 in water is quite rapid in sunlight. The rate is four times that of coal liquids, producing two photooxidant pools with reaction rate constants of 0.58/minute and 0.037/minute. The faster reacting photooxidant was tentatively identified as hydrogen peroxide and the slower reacting... 

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