Sensing the flux of volatile chemicals through the air-water interface
- Trent Univ., Peterborough, Ontario (Canada)
- Environment Canada, Downsview, Ontario (Canada)
- Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry
- Bovar Environmental, Toronto, Ontario (Canada)
There are several situations in which there is a need to assess the direction and magnitude of the flux across the air-water interface. Contaminants may be evaporating or absorbing in wastewater treatment systems in natural lake, river, estuarine and marine systems, and any attempt to compile a mass balance must include this process. In this study the authors review the theory underlying air-water exchange, then describe and discuss a sparging approach by which the direction and magnitude of the flux can be ascertained. The principle of the method is that a known flow rate of air is bubbled through the sparger and allowed to equilibrate with the water. The gas exiting the water surface is passed through a sorbent trap and later analyzed. The concentration, and hence the fugacity, of the contaminant in the sparged air can be deduced. In parallel, a similar flow of air from the atmosphere above the water is drawn through another sparger at a similar flow rate for a similar time and the trapped chemical analyzed giving the concentration and fugacity in the air. These data show the direction of air-water exchange (i.e. from high to low fugacity) and with information on the mass transfer coefficients and area, the flux. Successful tests were conducted of the system in a laboratory tank, in Lake Ontario and in Hamilton Harbour. Analyses of the traps showed a large number of peaks on the chromatogram many of which are believed to be of petroleum origin from fuels and vessel exhaust. The system will perform best under conditions where concentrations of specific contaminants are large, as occurs in waste water treatment systems. The approach has the potential to contribute to more accurate assessment of air-water fluxes. It avoids the problems of different analytical methodologies and the effect of sorption in the water column.
- OSTI ID:
- 351688
- Report Number(s):
- CONF-970677-; TRN: IM9927%%213
- Resource Relation:
- Conference: 90. annual meeting and exhibition of the Air and Waste Management Association, Toronto (Canada), 8-13 Jun 1997; Other Information: PBD: 1997; Related Information: Is Part Of 1997 proceedings of the Air and Waste Management Association`s 90. annual meeting and exhibition; PB: [7000] p.
- Country of Publication:
- United States
- Language:
- English
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