Abstract

A review is first presented of the present state of knowledge concerning the volatilization of organic contaminants from rivers. A series resistance model is derived which enables the volatilization rate to be calculated from a knowledge of river bulk resistance and the air and water near-interface resistances. The importance of Henry's Constant in determining the prevailing volatilization regime is demonstrated. It is shown that the considerable body of information on reaeration rates and particularly the more recent development of the Rathbun hydrocarbon-dye tracer technique provide valuable data on liquid phase resistance. The flux equation is coupled to the river mass flow balance to give an expression for contaminant concentration decay as a function of time or distance of flow. The feasibility of artificially aerating a stream to enhance volatilization is discussed and feasibility shown to be restricted to compounds of high Henry's Constant, except possibly in the presence of ice when volatilization rates may be reduced to undesirably low levels. The rate of sorption in reducing volatilization rate is discussed and quantified. Comparison between the few available literature data and the derived equations shows satisfactory agreement.

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