Laboratory studies were conducted to evaluate the influence of several processes on the behaviour and fate of synthetic volatile organic chemicals in an aqueous environment. Five organic priority pollutants, benzene, methylene chloride, tetrachloroethylene, toluene and trichloroethylene, were investigated to determine their susceptibility to the transformation processes of direct photolysis and hydrolysis under various pH, temperatures and concentrations. In addition, benzene, methylene chloride, tetrachloroethylene, toluene and trichloroethylene were examined for volatilization from the water surface as well as mass flux by diffusion into water.

The experimental findings for direct photolysis indicated that the susceptibility was negligible for all the selected organic compounds. However, methylene chloride, tetrachloroethylene and trichloroethylene were found to be susceptible to hydrolysis when the aquatic environment is basic and has an elevated temperature. Benzene, methylene chloride, tetrachloroethylene, toluene and trichloroethylene exhibited relatively rapid rates of volatilization and these rates were significantly influenced by the area to volume ratio. The overall Liquid film coefficients at the water-air interface for benzene, methylene chloride, tetrachloroethylene, toluene and trichloroethylene were observed to be 0.21, 0.69, 0.64 and 0.07 m/d, respectively, under the specified conditions.

The mass flux experiments indicated that, under quiescent conditions, the mass transfer occurring at the water-chemical interfaces of submerged pools of tetrachloroethylene and methylene chloride was low, thus providing an opportunity for clean up. Benzene and toluene floated to the surface and rapidly volatilized into the atmosphere. Mathematical equations have been developed to predict mass flux of such substances under given conditions.

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© CAWQ 1989