Air-Water Gas Transfer in Uniform Channel Flow

Transfer of low-solubility gas between air and flowing water is studied experimentally and through analysis of previous studies. The smallest turbulent motions are seen to have a theoretical advantage in overcoming interfacial resistance, and measurements of oxygen absorption rates are found to agree with small-eddy scaling. Though recent studies have emphasized large motions, this conflict is resolved by a conceptual framework incorporating both scales in terms of the distribution of near-surface turbulent energy dissipation rates. At higher Reynolds numbers, such as in natural streams, transfer rates are expected to be controlled by mean dissipative scales.