New Unified Equation for Wind-Driven Surficial Oxygen Transfer into Stationary Water Bodies

Wind-driven surficial oxygen transfer into stationary water bodies plays an important role in analyzing the fate and biochemical processes of environmentally important gases. This article (1) reviews research on oxygen and other gas transfers into non-moving, open water bodies, and (2) presents the synthesis of a new, unified equation for oxygen mass transfer coefficients based on gas transfer data published during the last 50 years. Both theoretical and empirically derived oxygen coefficients were reviewed using data derived from investigations in controlled wind tunnels, floating reaeration devices in open waters, and natural open waters. To facilitate the comparative analyses, gas transfer coefficient correlations for other gases were normalized to oxygen, and wind speeds were normalized to 10 m height. Wind was the major turbulence agent facilitating the gas transfer processes. Generally, low wind speed did not significantly influence the transfer coefficients. However, the transfer coefficients increased, even exponentially, with higher wind speeds. There were large variations among existing transfer coefficient correlations. Nonetheless, sufficient gas transfer data have been published in the last five decades to provide a solid basis for synthesizing a new unified oxygen transfer coefficient formula to estimate surficial oxygen transfer into treatment lagoons. The new unified equation for wind-driven surficial oxygen transfer is a function of Schmidt number, wind speed, and temperature.