A simple and low-cost open dynamic chamber for the versatile determination of methane emissions from aquatic surfaces

Abstract

Methane (CH₄) emissions from aquatic ecosystems require accurate monitoring in the context of climate change. Among the several methods for CH₄ flux measurement, open dynamic chambers (ODC) are a reliable option. This method consists of a floating chamber through which a carrier gas is constantly flowing, providing accurate flux measurement with high temporal resolution. However, this method requires expensive and heavy CH₄ analyzers with high sensitivity, as well as a carrier gas system that comprises a gas cylinder and a gas flow controller, among other components. This system involves significant weight and cost challenges, limiting method implementation in certain settings and hindering its wider adoption. To address these limitations, we developed a simplified ODC configuration using atmospheric air as the carrier gas and a light and relatively less expensive detector. We applied this method to a 450-ha urban lake with CH₄ emissions ranging from moderate diffusive to high ebullitive fluxes. Concurrent measurements using a high-sensitivity CH₄ analyzer allowed us to compare the accuracy of the simplified ODC method and to assess its advantages and disadvantages. Results show that our method provides accurate CH₄ flux measurements with a spatial resolution comparable to high-sensitivity analyzers. This offers a more cost-effective, straightforward, and lightweight alternative to high-sensitivity detectors and carrier gas systems, simplifying ODC deployment in aquatic ecosystems.