Volatilization of Chemicals

As a result, it was found that the release of trace metals was affected by temperature, and atmosphere. The volatility of chemical form of trace metals in raw coal and the chemical change of trace metals during high temperature heat processing were very important for the... 

The water to air ratio (Kw) when taken by itself can be used to represent the volatility of chemicals from aqueous solution. 

Dobbs, A. J., Cull, M. R. (1982) Volatilization of chemical relative loss rates and the estimation of vapor pressures. Environ. Pollut. Ser.B., 3, 289-298. 

Howard, C., and R. L. Corsi, Volatilization of Chemicals from Drinking Water to Indoor Air The Role of Residential Washing Machines, J. Air Waste Manage. Assoc., 48, 907-914 (1998). 

Vapor pressure is used for estimating the volatility of chemical compounds and the environmental fate of chemicals. This coefficient is also important in pharmaceutical studies, for example, for development of perfumes and pressurized aerosols. 

Many chemicals escape quite rapidly from the aqueous phase, with half-lives on the order of minutes to hours, whereas others may remain for such long periods that other chemical and physical mechanisms govern their ultimate fates. The factors that affect the rate of volatilization of a chemical from aqueous solution (or its uptake from the gas phase by water) are complex, including the concentration of the compound and its profile with depth, Henry s law constant and diffusion coefficient for the compound, mass transport coefficients for the chemical both in air and water, wind speed, turbulence of the water body, the presence of modifying substrates such as adsorbents in the solution, and the temperature of the water. Many of these data can be estimated by laboratory measurements (Thomas, 1990), but extrapolation to a natural situation is often less than fully successful. Equations for computing rate constants for volatilization have been developed by Liss and Slater (1974) and Mackay and Leinonen (1975), whereas the effects of natural and forced aeration on the volatilization of chemicals from ponds, lakes, and streams have been discussed by Thibodeaux (1979). 

In the following section some physicochemical properties of chemicals that affect the volatilization from soil are briefly introduced. Next, the factors influencing the volatilization process of a chemical from the soil and methods for measuring volatilization fluxes are discussed. Following, models that estimate the rate of volatilization of chemicals from soil are presented, and finally, some thermodynamic aspects of persistent organic chemicals and the concept of equilibrium partitioning are discussed. 

Several models have been proposed for estimating volatilization of chemicals incorporated into soil, but not all of them are applicable to a given situation. Moreover, no simple model for the estimating the volatilization rate for chemicals distributed and incorporated into soil, is available. The application of these complex models requires a number of input data, e.g. adsorption isotherm coefficients, diffusion coefficients, environmental properties, which in most cases are not experimentally known nor can be accurately predicted. 

Models Applicable to Volatilization of Chemicals from the Soil Surface... 

The thin film model thus far has been applied to the volatilization of chemicals dissolved in water. Chemical volatilization can also occur from a layer of nonaqueous phase liquid (NAPE) floating on a water surface (or spilled on the ground). NAPE refers to a liquid, such as a solvent or a liquid fuel, that does not readily dissolve in water and hence tends to remain as a separate liquid phase. There are two kinds of NAPE light NAPL... 

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