Accessible methodology to evaluate the behavior of methane emissions from a water body

Abstract

Lakes are important sources of methane (CH4) to the atmosphere, but these water bodies are currently considered the most uncertain components of the global CH4 budget. Here we propose a time-integrated air sampling approach to characterize the atmospheric CH4 concentration in the periphery of a lake, as an indicator of its CH4 emission behavior. Air samples were collected using vacuum vessels equipped with a shutoff valve and flux restrictors deployed at central buoys and peripheral sites to determine atmospheric CH4 concentrations (AM). The AM measured at peripheral stations (AMP) showed strong-to-moderate linear relationships with those from central buoys, as well as with CH4 fluxes at the water–air interface (MF), particularly under predominant wind directions and low calm frequencies. Even under less favorable conditions, such as high calm or variable wind directions, the accumulated signal remained coherent, demonstrating the ability of this strategy to integrate over time and detect consistent CH4 patterns. Multiple regression analysis showed that AMP considering only downwind periods was significantly explained by MF and the frequency of calm events, indicating that peripheral monitor-ing integrates both emission intensity and atmospheric transport. The relative variation in AMP, interpreted in the context of wind-driven variability, allows discrimination between weak and strong CH4 emission regimes in lentic systems, with larger AMP enrichments corresponding to periods of higher emissions. Compared with the static chamber technique, commonly used to estimate CH4 fluxes, this approach is less labor-intensive and more easily extrapolated to the simultaneous study of multiple lakes or large-scale assessments.