Volatilization of Multicomponent Contaminants

The maximum vapor pressure value that cau be established at the iuuer surface of the lamiuar flow layer iu air moviug over a soil surface is reached ouly wheu the surface is covered uuiformly by the coutamiuaut. This situatiou is almost impossible to fmd iu the subsurface, where a chemical is partially adsorbed ou the subsurface solid or dissolved iu the subsurface water, which reduces the vapor pressure below the equilibrium value of the pure compouud. 

Woodrow et al. (1986) assumed that the mixture of components (W ) is ideal, so that the volatilization of each component (W.) proceeds by a first-order process that is described by 

It is known that, in a water phase, immiscible liquids such as gasoline or other petroleum products may form multicomponent droplets of various forms and sizes, under dispersive conditions. These droplets are transported by convection and diffusion, which contributes to the contamination of fresh water systems. However, during droplet transport, more volatile substances partition to the gas phase at the droplet surface, leaving less volatile material that volatilizes more slowly. More volatile material still exists in the droplet interiors, and it tends to diffuse toward the surface because of concentration gradients created by prior volatilization. Different components in a droplet have different volatilization rates, which may vary significantly during droplet transport, and as a result, the contamination of fresh water is affected accordingly. 

Nye et al. (1994) studied the volatilization of single- and multicomponent liquids through soil columns, emphasizing differences between the two cases. For a single liquid, three stages were identified (1) soil sorbs the gas as it diffuses 

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