A Cost-Effective Automatic Chamber for Permanent CH4 and N2O Assessments inWetland Environments

Wetland ecosystems exhibit large spatial and temporal variability in terms of greenhouse gas (GHG) fluxes, necessitating new technologies to ensure that they are well-monitored. Both manual and automated chamber-based approaches are currently costly and thus limited either in spatial or temporal resolution. Following on from Wang et al. (2022), we propose a new, inexpensive autochamber (TraceCatch) for long-term outdoor installation. Costs for one unit are less than 800€ in total, making it affordable and scalable for long-term ecological research, also in lower income countries such as the global south. The system is based on gathering gas samples over two weeks into four gas bags on a high-frequency sampling schedule. TraceCatch is controlled using an Arduino Uno, connected to a peristaltic pump for sampling of chamber headspace air as well as a number of sensors for air temperature and humidity (SHT-41), air pressure (BMP280), and CO2 concentrations (K30FR; 0–5,000 ppm, 30 ppm resolution). The latter are used to track the sealing condition of the chamber. We validated the system using defined injection amounts of technical gas (100% CO2). In addition, the system was applied to measure GHG fluxes from three wetland cores placed inside three ecotrons (UGT EcoLab flex, manufactured by Umwelt-Geräte-Technik GmbH, Germany). Gas samples were collected 4 times a day for 2 weeks during a 1 hour chamber closure time at t0, t20, t40, t60 and subsequently analyzed using gas chromatography (Nexis GC-2030, manufactured by Shimadzu Corporation, Japan). Average GHG fluxes determined over the two-week period were then compared to single measurements obtained using multi-gas sensors (LI-COR LI-7820 and LI-7810 analyzers, manufactured by LI-COR Biosciences, USA). If adopted, the system’s low cost, scale and robustness for permanent field deployments could help improve wetland GHG monitoring, offering a cost-efficient and practical alternative to traditional methods for global-scale biogeochemical cycle assessments.