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Heterogeneity Matters: Aggregation Bias of Gas Transfer Velocity Versus Energy Dissipation Rate Relations in Streams
Author(s) -
Botter Gianluca,
Peruzzo Paolo,
Durighetto Nicola
Publication year - 2021
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2021gl094272
Subject(s) - dissipation , scaling , kinetic energy , streams , exponent , homogeneous , turbulence , mechanics , environmental science , scaling law , scale (ratio) , relative velocity , statistical physics , spatial heterogeneity , energy transfer , physics , thermodynamics , classical mechanics , mathematics , geometry , ecology , chemical physics , computer network , linguistics , philosophy , quantum mechanics , biology , computer science
The gas transfer velocity, k , modulates gas fluxes across air‐water interfaces in rivers. While the theory postulates a local scaling law between k and the turbulent kinetic energy dissipation rate ε , empirical studies usually interpret this relation at the reach‐scale. Here, we investigate how local k ( ε ) laws can be integrated along heterogeneous reaches exploiting a simple hydrodynamic model, which links stage and velocity to the local slope. The model is used to quantify the relative difference between the gas transfer velocity of a heterogeneous stream and that of an equivalent homogeneous system. We show that this aggregation bias depends on the exponent of the local scaling law, b , and internal slope variations. In high‐energy streams, where b > 1 , spatial heterogeneity of ε significantly enhances reach‐scale values of k as compared to homogeneous settings. We conclude that small‐scale hydro‐morphological traits bear a profound impact on gas evasion from inland waters.