Technical note: Pondi – a low-cost logger for long-term monitoring of methane, carbon dioxide, and nitrous oxide in aquatic and terrestrial systems

Understanding the complex dynamics of greenhouse gases (GHGs) such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes between aquatic and terrestrial ecosystems and the atmosphere requires extensive monitoring campaigns to capture spatial and temporal variations adequately. However, conventional commercial GHG analysers limit data collection due to their high costs, limited portability, cumbersome weight, and restricted field autonomy. To overcome these challenges, we developed the Pondi – a lightweight (0.8 kg) logger from cost-effective components tailored for long-term (weeks to months) continuous monitoring of CO2, CH4, and N2O concentrations in terrestrial and aquatic environments. Components for a Pondi cost approximately USD 750 (or AUD 1166) and require 6 h of specialised labour. The Pondi features solar panels for indefinite runtime, Global Positioning System (GPS) for tracking, an inertial measurement unit (IMU) for motion detection, and an optional microcontroller-powered add-on to support self-venting and additional sensors. The Pondi can be attached to either floating chambers to measure aquatic GHG emissions or terrestrial chambers to quantify respiration (with dark chambers) or net primary productivity (with transparent chambers). The Pondi is connected to a cloud-based system for real-time data access and remote configuration. The components for the Pondi are readily available in most countries, and basic engineering and IT skills are sufficient to assemble the device. By offering a practical, cost-effective, and reliable solution for GHG monitoring, the Pondi contributes to efforts to assess and mitigate anthropogenic GHG emissions.