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

Klaus, Marcus and Labasque, T. and Botter, G. and Durighetto, N. and Schelker, J. (2022). Unraveling the Contribution of Turbulence and Bubbles to Air-Water Gas Exchange in Running Waters. Journal of Geophysical Research: Biogeosciences. 127 :3 , e2021JG006520
[Research article]

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Abstract

Quantifying air-water gas exchange is critical for estimating greenhouse gas fluxes and metabolism in aquatic ecosystems. In high-energy streams, the gas exchange rate k is poorly constrained, due to an incomplete understanding of turbulence and bubble contributions to k. We performed a flume experiment with air bubble additions to evaluate the combined effects of turbulence and bubbles on k for helium, argon, xenon, and methane. We created contrasting hydraulic conditions by varying channel slope, bed roughness, water discharge, and bubble flux. We found that k increased from 1-4 to 17-66 m d(-1) with increases in turbulence and bubble flux metrics. Mechanistic models that explicitly account for these metrics, as well as gas diffusivity and solubility, agreed well with the data and indicated that bubble-mediated gas exchange accounted for 64-93% of k. Bubble contributions increased with bubble flux but were independent of gas type, as bubbles did not equilibrate with the water. This was evident through modeled bubble life and equilibration times inferred from bubble size distributions obtained from underwater sound spectra. Sound spectral properties correlated well with turbulence and bubble flux metrics. Our results demonstrate that (a) mechanistic models can be applied to separate free surface- and bubble-mediated gas exchange in running waters, (b) bubble life and equilibration times are critical for accurate scaling of k between different gases, and (c) ambient sound spectra can be used to approximate contributions of turbulence and bubbles.

Authors/Creators:Klaus, Marcus and Labasque, T. and Botter, G. and Durighetto, N. and Schelker, J.
Title:Unraveling the Contribution of Turbulence and Bubbles to Air-Water Gas Exchange in Running Waters
Series Name/Journal:Journal of Geophysical Research: Biogeosciences
Year of publishing :2022
Volume:127
Number:3
Article number:e2021JG006520
Number of Pages:16
Publisher:AMER GEOPHYSICAL UNION
ISSN:2169-8953
Language:English
Publication Type:Research article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution-Noncommercial-No Derivative Works 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Oceanography, Hydrology, Water Resources
(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Environmental Sciences (social aspects to be 507)
Keywords:piston velocity, channel, degassing, reaeration, hydrophone, bubble
URN:NBN:urn:nbn:se:slu:epsilon-p-116847
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-116847
Additional ID:
Type of IDID
DOI10.1029/2021JG006520
Web of Science (WoS)000777487700024
ID Code:27697
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
Deposited By: SLUpub Connector
Deposited On:05 May 2022 07:25
Metadata Last Modified:05 May 2022 07:31

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