Home About Browse Search
Svenska


Evaluating stream CO2 outgassing via drifting and anchored flux chambers in a controlled flume experiment

Vingiani, Filippo and Durighetto, Nicola and Klaus, Marcus and Schelker, Jakob and Labasque, Thierry and Botter, Gianluca (2021). Evaluating stream CO2 outgassing via drifting and anchored flux chambers in a controlled flume experiment. Biogeosciences. 18 , 1223-1240
[Journal article]

[img] PDF
2MB

Abstract

Carbon dioxide (CO2) emissions from running waters represent a key component of the global carbon cycle. However, quantifying CO2 fluxes across air-water boundaries remains challenging due to practical difficulties in the estimation of reach-scale standardized gas exchange velocities (k(600)) and water equilibrium concentrations. Whereas craft-made floating chambers supplied by internal CO2 sensors represent a promising technique to estimate CO2 fluxes from rivers, the existing literature lacks rigorous comparisons among differently designed chambers and deployment techniques. Moreover, as of now the uncertainty of k(600) estimates from chamber data has not been evaluated. Here, these issues were addressed by analysing the results of a flume experiment carried out in the Summer of 2019 in the Lunzer:::Rinnen - Experimental Facility (Austria). During the experiment, 100 runs were performed using two different chamber designs (namely, a standard chamber and a flexible foil chamber with an external floating system and a flexible sealing) and two different deployment modes (drifting and anchored). The runs were performed using various combinations of discharge and channel slope, leading to variable turbulent kinetic energy dissipation rates (1.5 x 10(-3) epsilon < 1 x 10(-1) m(2) s(-3)). Estimates of gas exchange velocities were in line with the existing literature (4 < k(600) < 32 m(2) s(-3)), with a general increase in k(600) for larger turbulent kinetic energy dissipation rates. The flexible foil chamber gave consistent k600 patterns in response to changes in the slope and/or the flow rate. Moreover, acoustic Doppler velocimeter measurements indicated a limited increase in the turbulence induced by the flexible foil chamber on the flow field (22 % increase in 8, leading to a theoretical 5 % increase in k(600)). The uncertainty in the estimate of gas exchange velocities was then estimated using a generalized likelihood uncertainty estimation (GLUE) procedure. Overall, uncertainty in k(600) was moderate to high, with enhanced uncertainty in high-energy set-ups. For the anchored mode, the standard deviations of k 6 00 were between 1.6 and 8.2 m d(-1), whereas significantly higher values were obtained in drifting mode. Interestingly, for the standard chamber the uncertainty was larger (+ 20 %) as compared to the flexible foil chamber. Our study suggests that a flexible foil design and the anchored deployment might be useful techniques to enhance the robustness and the accuracy of CO2 measurements in low-order streams. Furthermore, the study demonstrates the value of analytical and numerical tools in the identification of accurate estimations for gas exchange velocities. These findings have important implications for improving estimates of greenhouse gas emissions and reaeration rates in running waters.

Authors/Creators:Vingiani, Filippo and Durighetto, Nicola and Klaus, Marcus and Schelker, Jakob and Labasque, Thierry and Botter, Gianluca
Title:Evaluating stream CO2 outgassing via drifting and anchored flux chambers in a controlled flume experiment
Series Name/Journal:Biogeosciences
Year of publishing :2021
Volume:18
Page range:1223-1240
Number of Pages:18
Publisher:COPERNICUS GESELLSCHAFT MBH
ISSN:1726-4170
Language:English
Publication Type:Journal article
Article category:Scientific peer reviewed
Version:Published version
Copyright:Creative Commons: Attribution 4.0
Full Text Status:Public
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 106 Biological Sciences (Medical to be 3 and Agricultural to be 4) > Ecology
URN:NBN:urn:nbn:se:slu:epsilon-p-111221
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-p-111221
Additional ID:
Type of IDID
DOI10.5194/bg-18-1223-2021
Web of Science (WoS)000620573000001
ID Code:22849
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
Deposited By: SLUpub Connector
Deposited On:29 Mar 2021 07:43
Metadata Last Modified:29 Mar 2021 07:51

Repository Staff Only: item control page

Downloads

Downloads per year (since September 2012)

View more statistics

Downloads
Hits