The air/water exchange of volatile organic compounds from waters in the transient and turbulent regime

The air/water exchange velocity of thirteen volatile organic compounds was investigated in laboratory stirred tank experiments. A standardized setup was used so that the exchange of VOCs could be examined as a function of the level of turbulence, expressed by the Reynolds number. The exchange rate showed an exponential correlation with the level of turbulence. The commonly used relationship, in which the air/water exchange rate of volatile organic compounds is calculated from the reaeration rate by introducing a factor equal to the ratio of the diffusion coefficients, raised to the power n, showed an exponent n = 0.56 +/- 0.05. It was statistically proven that this relationship is valid both in the transient and turbulent regime of the water system. The imposed degree of turbulence did give rise to reaeration and volatilization rates of the same order as in riverine systems, so that the obtained functional relationship can be applied in these environmental systems. (C) 1998 Elsevier Science Ltd. All rights reserved.