Organic photochemistry. XIII. Simulated atmospheric photodecomposition rates of methylene chloride, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethylene, and other compounds

Photochemical Reactivity of Perchloroethylene: A New Appraisal

“…Finally, no attempts were made to reconcile the reactivity data obtained by Schuck and Doyle 13 and by Dilling, et al 9 with those of the other studies. The effects of the Schuck and Doyle chamber's unorthodox design (lamps were inside the chamber) and of the unrealistic radiation and reactant concentration conditions used by Dilling, et al are not well enough understood to permit meaningful comparisons with the other studies.…”

“…COC1 2 + CIO (8) In the absence of NO, main reaction products should be CCI3CCKO) and COCI2. In the presence of moderate concentrations of NO, O3 also should form through photolysis of NO2, as well as PAN-type products arising from the CCI3CO radical through reactions similar to those in smog chemistry for hydrocarbons/aldehydes.…”

“…For example, injection of small amounts of Cl 2 in irradiated PCE/ NO*/air systems caused a temporary but pronounced accel- eration of PCE consumption. 9 Also, presence of an effective Cl atom scavenger was observed to inhibit the PCE reaction. 9 ' 16 Finally, the pattern of PCE and O3 disappearing rapidly in parallel, displayed in the Lillian-Appleby, 6 - 16 Dimitriades-Joshi, 5 Sickles, et al, 23 and Joshi-Bufalini 32 studies, can be explained as caused by Cl atoms chain-reacting with and consuming both PCE and O3, the latter being as follows: 33…”

“…Similar results are also derived from the Dilling, et al data. 9 Dilling, et al reported that reduction of the initial PCE concentration in their smog chamber from 100 ppm to 10 ppm caused the normalized PCE consumption rate to be reduced by a factor of 2.9, down to a half-life of 11.2 h. Using again the rate equation R = k [PCE]" (where n > 1), and the Dilling, et al data, k and n are calculated to be 33.1 and 1.47, respectively, values that lead to a PCE consumption rate in the real atmosphere from 0.004%/h (hemispheric average) to 0.7%/h (urban maximum). The highest rates are higher than those of the ethane reaction with OH in the real atmosphere or of the PCE reaction with OH (Table III).…”

Toxicological Profile for Ethylbenzene

“…Using a nighttime nitrate radical concentration of 5x10 8 nitrate radicals per cm 3 , a half-life of approximately 26 days is estimated. Atmospheric degradation occurs more rapidly during summer months as opposed to winter since the concentration of hydroxyl radicals in the atmosphere peaks during summer (Ravishankara et al 1978;Singh et al 1981), and is also faster under photochemical smog conditions (Dilling et al 1976). Oxidation by-products from the reaction with hydroxyl radicals and nitrogen oxides include ethylphenols, benzaldehyde, acetophenone, and m-and p-nitroethylbenzene (Hoshino et al 1978).…”