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Measuring Dissolved Methane in Aquatic Ecosystems Using An Optical Spectroscopy Gas Analyzer
Published on: July 26, 2024
Dissolved methane in Indian freshwater reservoirs
G Narvenkar1, S W A Naqvi, S Kurian
1National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, 403004, India. sgayatree@gmail.com
Environmental Monitoring and Assessment
|February 12, 2013
Summary
Methane (CH4) emissions from Indian reservoirs are likely overestimated. Actual measurements show low surface water CH4 concentrations, suggesting limited atmospheric release from these freshwater bodies.
Area of Science:
- Environmental Science
- Climate Change Research
- Microbiology
Background:
- Tropical reservoirs are recognized sources of methane (CH4), a potent greenhouse gas, due to anaerobic microbial activity.
- Previous estimates suggested Indian reservoirs could emit up to 33.5 million metric tons of CH4 annually, but these were based on assumptions.
Purpose of the Study:
- To present the first direct measurements of dissolved CH4 concentrations in Indian freshwater reservoirs.
- To assess the actual potential for CH4 emissions from these reservoirs.
Main Methods:
- Dissolved CH4 concentrations were measured in eight Indian freshwater reservoirs.
- Water samples were analyzed to determine CH4 levels, particularly in subsurface layers and outflowing water.
Main Results:
- Most reservoirs exhibited seasonal anaerobic conditions and CH4 buildup in deeper waters (hypolimnia).
- Strong water stratification limited direct CH4 release to the atmosphere, resulting in generally low surface water CH4 concentrations (0.0028-0.305 μM).
- Significant CH4 accumulation was observed only in two small reservoirs at depths relevant for water usage, with low concentrations in outflowing water.
Conclusions:
- CH4 emissions from Indian reservoirs are likely significantly lower than previously estimated.
- Limited ventilation of CH4-rich subsurface waters and generally low surface concentrations indicate a lower atmospheric impact than assumed.
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