Abstract  To estimate the decomposition rates of chloro compounds in the atmosphere, we carried out laboratory studies on the photolysis rates of the four title compounds, six other chlorohydrocarbons, and 23 other organic compounds under simulated atmospheric conditions. In the presence of nitric oxide, vinylidene chloride, cis- and trans-dichloroethylene, trichloroethylene, and vinyl chloride decomposed at moderate rates (estimated half-lives of 5-12 h under bright sunlight) when compared with a series of standard hydrocarbons. Chlorobenzene, tetrachloroethylene, and 1,1,2-trichloroethane decomposed slowly (estimated half-lives 20-40 h). Methylene chloride and l,l,ltrichloroethane did not decompose (half-lives >250 and >>1700 h respectively). The photodecomposition rates of several chloro compounds were determined in mixtures with other organic compounds and also in the presence of nitrogen dioxide, ozone, chloral, acetaldehyde, chlorine, and phosgene. The presence of hydrocarbons reduced the decomposition rates of several chloroethylenes.

Abstract  Description of tables of property constants description of tables of equation coefficients synonyms list key for equation forms general references list of compound names.

Abstract  Photooxidation of cumene (isopropylbenzene) and pyridine in dilute solution in natural waters gives products characteristic of reactions with alkylperoxy (RO2⋅) and hydroxyl (HO⋅) radicals. On the basis of the rates of formation of the products, the average concentrations of RO2⋅ and HO⋅ are estimated to be about 10-9 and 10-17 mole per liter, respectively. The concentration of RO2⋅ is large enough that, for some classes of reactive chemicals, oxidation can be an important process in natural waters.

Abstract  HAPAB. Pesticides are an important group of synthetic chemicals which may or may not be degraded when released into the environment. Organophosphates are replacing the persistent organochlorines although some of these substitutes have persisted for 15 years. Some of the persistent pesticides like DDT and aldrin are modified either by microorganisms or through nonbiological means, but the product is not rapidly degraded. The polychlorinated biphenyls which have the highest chlorine content tend to accumulate and be magnified in the food chain like the persistent pesticides. Although generalizations are not evident concerning the effects of individual molecular substituents on resistance, the number and position of such substituents govern degradability in a number of dissimilar chemicals. Factors contributing to the recalcitrance of environmental chemicals include: nonexistence of an active organism; lack of similarity of the chemical to substrates of enzymes which catalyze breakdown; lack of sufficient energy or nutrients for growth of organism; toxicity of chemical to organism; failure of chemical to penetrate the cell; and low concentration or inaccessibility of substrate.

Abstract  Kinetics of the reaction of NO3 radicals with tetrahydrofuran, 1, 3-dioxolane and 1, 4-dioxane at 298 K +/- 1 K and 1.01 x 10(5) Pa were investigated using a relative rate method in a self-made Teflon chamber. The objective of this study was to assess the possible impact of these volatile organic compounds (VOCs) on the environment by studying their atmospheric degradation kinetics. Using gas chromatograph with a flame ionization detector(GC/FID), the measured reaction rate constant for NO3 with tetrahydrofuran was (5.36 +/- 1.93) x 10(-3) cm (molecule x s)(-1), which is in good agreement with the reported values, indicating the reliability of our experiment setup and methods. The reactions of NO3 radicals with 1, 3-dioxolane and 1, 4-dioxane were studied for the first time and the measured rate constants were (1.84 +/- 0.70) x 10(-15) cm3 x (molecule x s)(-1) and (3.20 +/- 0.67) x 10(16) cm3 x (molecule x s)(-1), respectively. The atmospheric lifetimes of these compounds have also been estimated based on the measured rate constants, which indicate that emissions of these compounds may have an impact on regional atmospheric environment.