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Effect of weir impoundments on methane dynamics in a river
Adam Bednařík1, Martin Blaser2, Anna Matoušů3
1Department of Ecology and Environmental Sciences, Laboratory of Aquatic Microbial Ecology, Faculty of Science, Palacky University in Olomouc, Olomouc, Czech Republic.
The Science of the Total Environment
|February 2, 2017
Summary
Weirs significantly alter river methane dynamics by increasing methane production and consumption in sediments. This leads to higher methane emissions to the atmosphere, particularly through ebullition upstream of the structures.
Area of Science:
- Environmental Science
- Geochemistry
- River Ecology
Background:
- Riverine methane (CH4) emissions are a significant component of global greenhouse gas budgets.
- The impact of anthropogenic structures like weirs on riverine CH4 dynamics is not fully understood.
Purpose of the Study:
- To investigate the role of weir impoundments in riverine methane dynamics.
- To quantify CH4 concentration, oxidation, and emissions in weir-altered river stretches.
- To determine the influence of sediments on CH4 production and consumption pathways.
Main Methods:
- Field measurements of CH4 concentration, water column oxidation, and atmospheric emissions (diffusion and ebullition).
- Sediment sampling to assess CH4 production and oxidation potentials.
- Analysis of methanogenic pathways, including hydrogenotrophic methanogenesis.
Main Results:
- CH4 surface water concentration increased 7.5-fold over a 16km river stretch containing weirs.
- Microbial CH4 oxidation in the water column was substantial, contributing to CH4 removal.
- Total CH4 emissions were highest upstream of weirs, with ebullition being the dominant pathway (95.8%).
- Sediment CH4 production and oxidation potentials were significantly higher upstream of weirs.
- Hydrogenotrophic methanogenesis was the predominant pathway for CH4 production in sediments upstream of weirs.
Conclusions:
- Weirs significantly influence riverine CH4 dynamics by altering sediment processes.
- Increased CH4 production and consumption in sediments near weirs lead to elevated atmospheric CH4 emissions.
- Weir impoundments represent important hotspots for riverine methane cycling and emission.
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