the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Gas exchange velocities (k600), gas exchange rates (K600), and hydraulic geometries for streams and rivers derived from the NEON Reaeration field and lab collection data product (DP1.20190.001)
Abstract. Air-water gas exchange is essential to understanding and quantifying many biogeochemical processes in streams and rivers, including greenhouse gas emissions and metabolism. Gas exchange depends on two factors, which are often quantified separately: 1) the air-water concentration gradient of the gas and 2) the gas exchange velocity. There are fewer measurements of gas exchange velocity compared to concentrations in streams and rivers, which limits accurate characterization of air-water gas exchange (i.e., flux rates). The National Ecological Observatory Network (NEON) conducts SF6 gas-loss experiments in 22 of their 24 wadeable streams using standardized methods across all experiments and sites, and publishes raw concentration data from these experiments on the NEON data portal. NEON also conducts NaCl injections that can be used to characterize hydraulic geometry at all 24 wadeable streams. These NaCl injections are conducted both as part of the gas-loss experiments and separately. Here, we use these data to estimate gas exchange and water velocity using the reaRates R package. The dataset presented includes estimates of hydraulic parameters, cleaned raw concentration SF6 tracer-gas data (including removing outliers and failed experiments), estimated SF6 gas loss rates, normalized gas exchange velocities (k600, m d−1) and normalized depth-dependent gas exchange rates (K600, d−1). This dataset provides one of the largest compilations of gas loss experiments (n = 339) in streams to date. This dataset is unique in that it contains gas exchange estimates from repeated experiments in geographically diverse streams across a range of discharges. In addition, this dataset contains information on the hydraulic geometry of all 24 NEON wadeable streams, which will support future research using NEON aquatic data. This dataset is a valuable resource that can be used to explore both within- and across-reach variability in the hydraulic geometry and gas exchange velocity in streams.
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Status: final response (author comments only)
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RC1: 'Comment on essd-2024-330', Anonymous Referee #1, 06 Sep 2024
Aho et al. presents a large dataset of gas exchange velocities (k600) and gas exchange rates (K600) along with hydraulic geometries from 22 stream and river sites across the United States. This dataset is based on rigorous field experiments and measurements and is the largest gas exchange dataset I have ever seen. The value of the dataset is to facilitate key research questions such as riverine greenhouse gas (GHG) emissions and river metabolism and help understand the river ecological processes and biogeochemical fluxes. The manuscript is well-organized and straightforward to follow. The field experiments, data collection, data processing, and data description are all described in great details, although more information is needed for some aspects. Generally, I endorse the publication of this work in ESSD. I have the following specific comments need to be addressed.
L64: The term “𝑘600” and “𝐾600” should be defined and/or explained as they appear first time in the main text. Those two parameters look very similar (differ in non-capital and capital K) and they may confuse the readers. An explanation here would be very helpful.
L76: Why use SF6 as tracer gas? SF6 is a very potent GHG that has 23500 times greater global warming potential than CO2. Such large-scale experiments may cause environmental burdens.
L83: How was the tracer gas sample collected? Using headspace equilibrium method? More details are needed.
L87: How was the tracer SF6 samples analyzed?
L90: Can you plot the discharge hydrograph and marked when the tracer experiments were conducted? Histograms of discharge with tracer experiment marks on them are also acceptable. These graphs, which can be put in the supplement, will clearly show the representativeness of the experiments with flow regimes.
L368: Scaling relationships between k600 and hydraulics parameters such as velocity and channel slope would also be very useful for future users to estimate k600. I suggest the authors provided the equations between k600 and velocity and channel slope if that’s feasible.
L418: Can you go a step forward and provide these predictive models of gas exchange in this paper? With such comprehensive dataset in-hand, those models should be easy to fit (see the comment above).
Citation: https://doi.org/10.5194/essd-2024-330-RC1 -
AC3: 'Reply on RC1', Kelly Aho, 04 Oct 2024
Thank you for these suggestions! Please see https://doi.org/10.5194/essd-2024-330-AC1 for details on how we addressed each one.
Citation: https://doi.org/10.5194/essd-2024-330-AC3
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AC3: 'Reply on RC1', Kelly Aho, 04 Oct 2024
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RC2: 'Comment on essd-2024-330', Liwei Zhang, 07 Sep 2024
This dataset presents a large compilations of gas exchange related estimates based on gas loss experiments in streams across a range of discharges. It will be an important resource for the aquatic biogeochemistry community in general. Such compilation is necessary in order to better quantify the role and contribution of fluvial systems to greenhouse gas emissions, as well as to better identify current geographic gaps. The paper is structured in a good way that allows readers to follow easily. I have only few suggestions and minor comments in the hope that these can be helpful to the authors. Thanks to the authors for this important contribution to the field, and I’d like to see this work could be published in ESSD.
Line by Line Comments:
L31: I noticed the authors cited Rocher-Ros et al., 2023, so I wonder if the authors are able to provide some discussion about missing information of ebullitive k for CH4.
L77: It seems like these experimented streams are in small size. This raises the question of whether the methodologies and conclusions drawn from this study can be reliably extrapolated to the context of big rivers.
Please indicate the dates or seasons of experiments somewhere in the methods, because these are key information regarding discharge, velocity, water depth, etc.
Citation: https://doi.org/10.5194/essd-2024-330-RC2 -
AC2: 'Reply on RC2', Kelly Aho, 04 Oct 2024
Thank you for these suggestions! Please see https://doi.org/10.5194/essd-2024-330-AC1 for details on how we addressed each one.
Citation: https://doi.org/10.5194/essd-2024-330-AC2
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AC2: 'Reply on RC2', Kelly Aho, 04 Oct 2024
- AC1: 'Comment on essd-2024-330', Kelly Aho, 04 Oct 2024
Data sets
Gas exchange velocities (k600), gas exchange rates (K600), and hydraulic geometries for streams and rivers derived from the NEON Reaeration field and lab collection data product (DP1.20190.001) ver 1 K. S. Aho et al. https://doi.org/10.6073/pasta/8faa6ed1b1d8d1e7ad6c9e897bcacc49
Model code and software
NEONScience/NEON-reaeration: v0.0.2 K. Cawley et al. https://doi.org/10.5281/zenodo.12786089
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