Eosense was founded by soil scientists and here’s where we get to talk about the science behind our products. Check out our blog for more and contact us if you think we’d be interested in your application or research.
Soils naturally produce and consume gases through various mechanisms. For example, during the decomposition of organic matter, aerobic bacteria and fungi consume carbon compounds and oxygen and produce the greenhouse gas Carbon Dioxide (CO2).
The passage of produced or consumed gases across the soil surface is what is commonly referred to as soil gas flux. This flux is usually expressed as a quantity of gas per unit area per time. For instance, we might measure CO2 fluxes in units of grams per meter squared per hour (g/m2/h). Fluxes from the soil surface can be positive (passing from the soil to the atmosphere) or negative (passing from the atmosphere to the soil) depending on the process that is generating the flux.
By measuring these soil gas fluxes, researchers are able to make inferences about the processes that produced the gases. For example, it is commonly observed the CO2 fluxes increase exponentially with increasing temperature, indicating the natural chemical and biological processes that produce CO2 in the soil are strongly temperature dependent.
Forced Diffusion (FD) is a method to measure the flux of gases from the soil surface. Traditionally, these measurements are performed using either open or closed chamber systems, which use mechanical action to trap gases that are subsequently analyzed to calculate the rate of flux. These traditional approaches are prone to mechanical failure in harsh environments particularly those with heavy snow or ice load.
FD is a membrane-based steady-state approach for measuring gas flux. It was born from the need to have a reliable, low-power and low-maintenance method for measuring gas fluxes in harsh environmental conditions. By carefully characterizing the membrane used in the eosFD instruments, we are able to force the chamber gas concentration to a specific and stable value, which is linearly correlated to the gas flux rate. Unlike commonly used static and dynamic chambers, the FD approach does not require external moving parts allowing it to be deployed in the harshest conditions for extended periods without intervention.
To learn more about FD, please take a look at our peer-reviewed publications:
- Risk, D., Nickerson, N., Creelman, C., McArthur, G., Owens, J. (2011) Forced Diffusion soil flux: A new technique for continuous monitoring of soil gas efflux. Agricultural and Forest Meteorology, 151(12): 1622-1631.
- Lavoie, M., Risk, D., Owens, J. (2012) A new method for real time monitoring of soil CO2 efflux. Methods in Ecology and Evolution, 3(5): 889-897.
- Risk, D., Lee, C.K., MacIntyre, C., Cary, S.C. (2013) First year-round record of Antarctic Dry Valley soil CO2 flux. Soil Biology and Biochemistry, 66: 193-196.
- Evaluating Gas Emission Measurements Using Minimum Detectable Flux (MDF)
- Biases of Temporally Sparse Data and Measurement Scheduling on Flux Estimates
- Sizing Solar Power for Off-grid Field Studies
- Soil Gas Flux Factors in a Hilly Tropical Forest (Silver Lab, UC Berkeley)
- Carbon Sequestration in a Drought-Stressed California River Delta (Baldocchi Lab, UC Berkeley)
- Agricultural Gas Flux Measurements in Strawberry Fields (Dr. Los Huertos, Pomona College)
- From Riverine to Estuarine (Cow Bay Watershed, Nova Scotia, Canada)
- Methods for Surveying Aqueous CO2 in the Field (Literature Overview)
Header photo credit: Kathleen Lohse, CZO (EART 1331872 and USDA ARS)