A novel, low-cost floating chamber design for semi-automatic measurements of CO2 and CH4 emissions from ponds and ditches

Barbara Vergara Niedermayr¹,Danica Antonijevic,Oscar Monzón,and Matthias Hoffmann

Barbara Vergara Niedermayr et al. Barbara Vergara Niedermayr¹, Danica Antonijevic, Oscar Monzón, and Matthias Hoffmann

• ¹Universität Potsdam, Potsdam, Germany (bvergaraniedermayr@gmail.com)
• ²Leibniz-Zentrum für Agrarlandschaftsforschung (ZALF) e.V.

• ¹Universität Potsdam, Potsdam, Germany (bvergaraniedermayr@gmail.com)
• ²Leibniz-Zentrum für Agrarlandschaftsforschung (ZALF) e.V.

Due to the large number of small and strongly anthropogenic influenced ponds (area <1 ha; IPCC 2019) and ditches there is a substantial emission of GHG, originating globally from open water (e.g., Peacock et al. 2017, Holgerson & Raymond 2016). Within those systems, high nutrient loadings from surrounding agriculture as well as low oxygen levels yield in N₂O and especially CH₄ emissions, sometimes exceeding those of small natural waterbodies many times over. The impact of land use and land use change on GHG emission regimes of these strongly anthropogenic influenced small systems is however still fairly unknown due to a lack of more broad data sets, exceeding single years and/or single case studies. The reason for this lies in the sheer variability of these systems (e.g., land use, underlying environmental conditions, hydrology, soil type, intensity of anthropogenic disturbances, etc.) as well as in the complexity to perform GHG emission measurements at a great number of locations with limited resources. The latter is even more of a problem, when considering the usually high cost-insensitivity of GHG emission measurements, as well as the persistence of an underrepresentation of data from developed or developing countries in e.g., Southeast Asia and or sub-Saharan Africa due to the long-term focus in GHG research on the northern hemisphere.

Here we present first results of an inexpensive, semi-automatic, do-it-yourself (DIY) floating chamber design, which can be used for in-situ measurements of CO₂ and CH₄ emissions from ponds and ditches. The floating chamber design consists of a star-shaped floating body (“rose dich”) with a cantered PVC chamber (A: 0,194 m²; V: 0,63m³. Low-cost NDIR-Sensors were attached to the chamber, for measuring CO₂ (SCD30; 400-5,000 ppm, ± 50 ppm accuracy) and CH₄ concentrations (Figaro Gas-Sensor TGS-2611; …). Environmental conditions during chamber deployment were recorded using a DHT-22 (humidity and temperature) and a BMP280 (air pressure) sensor device. All sensors were connected to a Bluetooth enabled, battery powered, compact microcontroller-based logger unit for data visualization and storage. Measured CO₂ and CH₄ emissions from ditches and ponds obtained on three locations spread over NE Germany were validated against in parallel performed GHG flux measurements using evacuated glass bottles for air sampling and subsequent GC-14A and GC-14B analyses (Shimadzu Scientifec Instruments, Japan).

 

First results indicate a generally good overall agreement of measured CO₂ and CH₄ emissions. Thus, the presented, semi-automatic floating chamber design might help to broaden the data basis/representativeness of GHG emission estimates of the globally relevant, small, strongly anthropogenic influenced ponds and ditches.

 

Keywords: Land use change, greenhouse gas emissions, low-cost floating chamber, semi-automatic measurements of CO₂ and CH₄, anthropogenic pond and ditches