A laboratory method for testing the volatility from aqueous solution: first results and comparison with theory.

The mobility of a chemical in the environment is often determined by its volatilization from aqueous solution, especially if it shows poor water solubility and/or high vapor pressure. A small laboratory apparatus is described which allows the simulation of the volatilization process from a stirred water body with well-defined wind velocities and water temperatures. In experiments with naphthalene, pentachlorophenol, trichloroethene, and di(2-ethylhexyl)phthalate, substance concentrations in the water body decrease exponentially, in accordance with theory. Half-residence times are found to be independent of wind velocity (v less than 1 m sec-1) or air humidity, but are strongly dependent on temperature. The measured substance fluxes through the water surface are comparable with theoretical values. In the case of pentachlorophenol, which partly dissociates in aqueous solution, the volatility is controlled by the pH value of the solution.