Technical Note: Cost-efficient approaches to measure carbon dioxide (CO₂) fluxes and concentrations in terrestrial and aquatic environments using mini loggers

Abstract. Fluxes of CO₂ are important for our understanding of the global carbon cycle and greenhouse gas balances. Several significant CO₂ fluxes in nature may still be unknown as illustrated by recent findings of high CO₂ emissions from aquatic environments, previously not recognized in global carbon balances. Therefore, it is important to develop convenient and affordable ways to measure CO₂ in many types of environments. At present, direct measurements of CO₂ fluxes from soil or water, or CO₂ concentrations in surface water, are typically labor intensive or require costly equipment. We here present an approach with measurement units based on small inexpensive CO₂ loggers, originally made for indoor air quality monitoring, that were tested and adapted for field use. Measurements of soil–atmosphere and lake–atmosphere fluxes, as well as of spatiotemporal dynamics of water CO₂ concentrations (expressed as the equivalent partial pressure, pCO_2aq) in lakes and a stream network are provided as examples. Results from all these examples indicate that this approach can provide a cost- and labor-efficient alternative for direct measurements and monitoring of CO₂ flux and pCO_2aq in terrestrial and aquatic environments.