Volatilization of Organic Chemicals

Ince N, Inel Y. 1989. Volatilization of organic chemicals from water. Water Air Soil Pollut 47 71-80. 

Spencer, W.F., Cliath, M.M., Jury, W.A., Zhang, L.Z. (1988) Volatilization of organic chemicals from soil as related to their Henry s law constants. J. Environ. Qual. 17(3), 504-509. 

CHAPTER 11 Estimation of the volatilization of organic chemicals from soil (E. 

Estimation of the Volatilization of Organic Chemicals from Soil... 

A comprehensive model for the estimation of the volatilization of organic chemicals from soil surfaces should take, of course, explicitly into account all the above factors. Models developed for estimating volatilization rates are based on equations describing the rate of movement of the chemical to the surface by diffusion and/or by convection, and away from the surface through the air boundary layer by diffusion [10-16]. Additionally, the part of the chemical in soil that will be lost by volatilization depends on the resistance of the chemical to degradation. The application of most of these models... 

As mentioned by Mackay [43], the best enviromnental model is the least bad set of simplifying assumptions that yields a model which is not too complex, but at the same time sufficiently detailed to be useful. A comprehensive model for the estimation of the volatilization of organic chemicals from soil surfaces should take, of course, explicitly into account aU the factors mentioned in the previous section. The complexity and difficulty of incorporation of the above factors into a single model clearly indicate the expected shortcomings and uncertainties of the theoretical studies of soil volatilization. This is because the approximations that are used in the existing developed models do not sufficiently explain or cover the great number of complexities during the volatilization process. 

The opening chapter An introduction to modelling of pollutants in the environment by Trevor M. Letcher demonstrates convincingly that equilibrium concepts and simple models lead to realistic predictions of, for example, the concentration of a polychlorinated biphenyl in the fishes of the St. Lawrence River. Relative solubilities expressed by octanol-water and air-water partition coefficients play a crucial role for estimating the distribution of chemicals in the environment. This is pointed out in the introductory chapter as well as in others such as Estimation of volatilization of organic chemicals from soil by Epaminondas Voutsas. 

Volatilizational loss of chemicals from water to air is an important fate process for chemicals with low aqueous solubility and low polarity. Many chemicals, despite their low vapor pressure, can volatilize rapidly owing to their high activity coefficients in solution. Volatilizational loss from surfaces is a significant transport process. Volatilization of organic chemicals from the soil surface is complicated by other variables. There is no simple laboratory... 

Essential is also used as the adjective form of the noun essence The mixtures of substances that make up the fragrant material of plants are called essential oils because they contain the essence that is the odor of the plant The study of the composition of essential oils ranks as one of the oldest areas of organic chemical research Very often the principal volatile component of an essential oil belongs to a class of chemical sub stances called the terpenes... 

Thermal Desorption. Thermal desorption is an innovative treatment that has been appHed primarily to soils. Wastes are heated to temperatures of 200 to 600°C to increase the volatilization of organic contaminants. Volatilized organics in the gas stream are removed by a variety of methods including incineration, carbon adsorption, and chemical reduction. 

Glotfelty DE, Schomburg CJ. 1989. Volatilization of pesticides from soil. Reactions and movement of organic chemicals in soils. SSSA Special Publication No. 22, 181-207. 

The van t Hoff equation also has been used to describe the temperature effect on Henry s law constant over a narrow range for volatile chlorinated organic chemicals (Ashworth et al. 1988) and chlorobenzenes, polychlorinated biphenyls, and polynuclear aromatic hydrocarbons (ten Hulscher et al. 1992, Alaee et al. 1996). Henry s law constant can be expressed as the ratio of vapor pressure to solubility, i.e., pic or plx for dilute solutions. Note that since H is expressed using a volumetric concentration, it is also affected by the effect of temperature on liquid density whereas kH using mole fraction is unaffected by liquid density (Tucker and Christian 1979), thus... 

Jury, W.A., Russo, D., Streile, G., El Abd, H. (1990) Evaluation of volatilization by organic chemicals residing below the soil surface. Water Resources Res. 26, 13-26. 

Mclachlan, M., Mackay, D., Jones, P.H. (1990) A conceptual model of organic chemical volatilization at waterfalls. Environ. Sci. Technol. 24, 252-257. 

Kilzer L, Scheunert I, Geyer H, et al. 1979. Laboratory screening of the volatilization rates of organic chemicals from water and soil. Chemosphere 10 751-761. 

Wilcockson, J. B. and Gobas, F.A.P.C. 2001, Thin-film solid-phase extraction to measure fugacities of organic chemicals with low volatility in biological samples. Environ. Sci. Technol. 35 1425-1431. 

In the late nineteenth century and up to World War II coal was the major starting material for the organic chemical industry. When coal is heated in the absence of oxygen, coke and volatile by-products called coal tars are created. All sorts of organic chemicals can be isolated from coal tar - benzene, toluene, xylenes, ethylbenzene, naphthalene, creosotes, and many others (including Hofmann and Perkin s aniline). The organic chemical industry also draws upon other natural products, such as animal fats and vegetable oils, and wood by-products. 

Abiotic transformation of contaminants in subsurface natural waters result mainly from hydrolysis or redox reactions and, to lesser extent, from photolysis reactions. Complexation with natnral or anthropogenic ligands, as well as differential volatilization of organic compounds from multicomponent hquids or mixing with toxic electrolyte aqueous solutions, may also lead to changes in contaminant properties and their environmental effects. Before presenting an overview of the reactions involved in contaminant transformations, we discuss the main chemical and environmental factors that control these processes. 

Cramer PH, Boggess KE, Hosenfeld JM, et al. 1988. Determination of organic chemicals in human whole blood Preliminary method development for volatile organics. Bull Environ Contam Toxicol 40 612-618. 

Soil vapor extraction (SVE) (also called vacuum extraction, soil venting, or in situ vaporization) is used to remove volatile organic compounds (VOCs) and some semivolatile organic compounds (SVOCs) from contaminated soil. SVE systems apply a vacuum in an extraction well to remove soil vapors. This creates a negative pressure that causes the volatilization of some chemicals in the vadose zone of the soil. The technology has also been used to extract non-aqueous-phase liquid (NAPE). Contaminant volatilization is often enhanced through the use of air injection wells to supply unsaturated air into the vadose zone of the soil. 

Probably the most important advantage is that they have no measurable vapor pressure. Unlike conventional solvents used in the indusbial syntheses of organic chemicals, they are nonvolatile and therefore do not emit vapors. With ionic liquids, you do not have the same concerns as you have with volatile organic solvents, which can contribute to air pollution. Ionic liquid chemistry is a very new area that is not only extremely interesting from a fundamental chemistry point of view, but could also have a very large impact on industry (Freemantle, 2000). 

Guicherit, R. Schulting, F.L. (1985) The occurrence of organic chemicals in the atmosphere of the Netherlands. Sci. total Environ., 43, 193-219 Hajimiragha, H., Ewers, U., Brockhaus, A. Boettger, A. (1989) Levels of benzene and other volatile aromatic compounds in the blood of non-smokers and smokers. Int. Arch, occup. 

Analytical Methods for the Determination of Volatile Nonpolar Organic Chemicals in Water and Water-Related Environments... 

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