A lightweight laser-based gas sensor and balloon UAV for spatial quantification of greenhouse gas fluxes in peatlands

Drained peatlands can act as significant sources of greenhouse gases (GHG), in contrast to undisturbed peatlands which act as long-term carbon sinks. Rewetting measures can help to reduce the GHG emissions, however, obtaining accurate GHG flux estimates to evaluate the effectiveness of these measures is complicated by the spatial heterogeneity of many peatland sites.

To improve the spatial coverage of GHG flux estimates in these sensitive ecosystems, a new lightweight laser-based sensor is being developed capable of measuring concentrations of CO₂, CH₄, and N₂O plus water vapor down to the ppb level. This sensor has a low power consumption and a total mass of less than 1 kg, allowing it to be mounted on a steerable balloon-drone (lighter than air unmanned aerial vehicle, LTA-UAV).

This study focuses on the development and evaluation of a measurement and analysis framework that will be applied to the LTA-UAV-borne sensor observations. Surface-atmosphere GHG fluxes will be estimated using two approaches: a vertical flux-gradient method and a mass continuity method, both based on concentration profiles acquired along vertical and horizontal flight paths. Profile data for testing these approaches are obtained using a tower-based gas analyser at an eddy-covariance instrumented peatland site. These measurements are used to assess the methodologies and the potential of the LTA-UAV system for GHG flux estimation at heterogeneous peatland sites.