Unravelling the Contribution of Turbulence and Bubbles to Air-Water Gas Exchange in Running Waters

Aquatic ecosystems exchange gases with the atmosphere and this exchange is critical for many ecosystem processes and the global greenhouse gas cycle. However, it is difficult to determine how fast gases exchange with the atmosphere, especially in running waters where bubbles can speed up the exchange of certain gases. Here, we provide a data set on air-water gas exchange velocities, collected during an outdoor flume experiment. We used experimental stream channels to create a wide range of flow conditions, and tested how these conditions effect the rate at which different gases in the water exchange with the atmosphere. Besides gas exchange velocities for direct air-water exchange and exchange mediated by bubbles, the data set also contains data on, among others, flow conditions, turbulent kinetic energy dissipation rate, bubble flux rate and ambient underwater sound pressure signatures. The experimental design and data are described in articles by Vingiani et al. (2021) and Klaus et al. (2022). main data contributions: (1) Gas exchange velocity estimates based on mass balance of various gases in flume water Concentrations of helium, xenon, argon och methane were measured in the in- and outlet water of the flumes using mass-spectrometry . A mass balance of the gases yielded air-water gas exchange velocities. (2) turbulent kinetic energy dissipation estimates based on Acoustic Doppler Velocimetry Three-dimensional flow velocities were measured at 24 locations per flume using an Acoustic Doppler Velocity meter. Spectral analysis was applied to derives turbulent kinetic energy dissipation rates. (3) sound pressure signatures derived from Hydrophone and microphone recordings Ambient sound was recorded at 12 locations per flume using a hydrophone and a microphone. Spectral analysis was used to derive sound signatures associated with water flow / turbulence and air bubbles.