Applications and Uses of Oxygen Sensors

About Oxygen Sensors

Oxygen availability determines the rate of many biological and chemical processes and is required for aerobic respiration. It is the absolute amount of oxygen (measured as partial pressure in kilopascals) that nearly always determines oxygen availability, but we think of oxygen as a percent of the total number of molecules in the air (20.95 %). The best example of this is the oxygen on top of Mount Everest, which is 20.95 %, but most climbers need supplemental oxygen to get to the top.

There are two types of oxygen sensors: those that measure gaseous O2 and those that measure dissolved oxygen in a solution. The Apogee sensor measures gaseous O2 as a percentage. Gas sensors read out in percent because this value does not change with temperature or pressure.

There are multiple techniques for measuring gaseous oxygen. Three widely used approaches for environmental applications are galvanic cell sensors, polarographic sensors, and optical sensors. The Apogee sensor is a galvanic cell type that operates by electrochemical reaction of oxygen with an electrolyte, which produces an electrical current. The electrochemical reaction consumes a small amount of oxygen in the reaction in order to produce the current flow and subsequent mV output. The current flow between the electrodes are proportional to the oxygen concentration being measured, and an internal bridge resistor is used to provide the mV output. The mV output responds to the partial pressure of oxygen in air.

Typical Applications

Typical applications of oxygen sensors include:

  • measurement of O2 in laboratory experimenets
  • monitoring gaseous O2 in indoor environments for climate control
  • monitoring of O2 levels in compost piles and mine tailings
  • monitoring redox potential in soils
  • determination of resiration rates through measurement of O2 consumption in sealed chambers
  • measurement of O2 gradients in soil/porous media
DeAngelis, K.M., Allgaier, M., Chavarria, Y., Fortney, J.L., Hugenholtz, P., Simmons, B., Sublette, K., Silver, W.L., and Hazen, T.C. | PLoS ONE
The best understood method of lignin breakdown if by dioxygenases in fungi, which generally require oxic conditions provided by soil respiration. In the quest for a robust, effective and inexpensive method of breaking down lignin for use in biofuels, this article investigates the role of anaerobic microorganisms in the tropical rain forests of Puerto Rico. Apogee sensors were used to measure the soils oxygen concentration around bio-traps used to study the organisms responsible for this breakdown, and the data collected “suggests that in low fluctuating redox soils, bacteria could play a role in anaerobic lignin degradation."
Hall, S.J., Silver, W.L., and Amundson, R. | Biogeochemistry
This article explores the biogeochemical potential of Earth’s driest exosystem, the Atacama Desert, arid and semi-arid soils with extremely low levels of organic carbon and moisture. Apogee sensors were used to determine if the soils were anoxic or oxic during their experiments. The study data show that more CO2 was produced under oxic conditions than in sub-oxic conditions in soil sites with existing vegetation and therefore higher C concentrations, which suggests the presence of aerobic microbial decomposers. This is in contrast with the most arid and lowest carbon sites where CO2 production is predominantly abiotic.
Kallestad, J.C., Sammis, T.W., and Mexal, J.G. | oil Science Society of America Journal
This study compares two types of oxygen sensors, galvanic and chemi-luminescent, for use in monitoring soil air oxygen in flood-irrigated Pecan orchards. Apogee’s galvanic oxygen sensors with the diffusion head accessory were deployed at multiple depths and continuous data was collected. The spectrometer–coupled chemical sensor was used to field analyze gas samples from diffusion chambers. “The responsiveness of the galvanic sensor and its capability to continuously gather hourly data makes it superior to methods dependent on manual sample collection. Galvanic sensors were adequately suited for long-term in situ use in agricultural soil when housed in appropriate diffusion chambers.”
Liptzin, D., Silver, W.L., and Detto, M. | Ecosystems
Temporal and spatial patterns in soil redox are not well understood and this study investigates these variations in tropical forests. Soil air oxygen levels, measured with Apogee sensors, were found to be significantly lower in upper elevation cloud forest than in lower elevation wet tropical forest, where interestingly the concentration of oxygen changed as much as 10 % in one day.
Phillip, E. | Journal of Environment Quality
Raciti, S.M., Burgin, A.J., Groffman, P.M., Lewis, D.N., and Fahey, T.J. | Journal of Environment Quality
Rubol, S., Silver, W.L., and Bellin, A. | Science of The Total Environment
Glenn, D. M., Cooley, N., Walker, R., Clingeleffer, P. & Shellie, K. | HortScience
U, K.T.P., Xu, L., Ideris, A.J., Kochendorfer, J., Wharton, S., Rolston, D.E., and Hsiao, T.C.
McNicol, G., W.L. Silver | Biogeochemistry
J. Nelson | Utah State University - Hydroponics/Soilless Media
Burgin, A.J., P.M. Groffman | Journal of Geophysical Research
Ahn, H.K., W. Mulbry, J.W. White, S.L. Kondrad | Bioresource Technology
Z.M. Aldhafeeri | University of Ottawa
Soil Oxygen Concentration
Quasi-continuous measurements of bulk soil oxygen concentration in managed and natural ecosystems.

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Soil Respiration

Apogee oxygen sensors can be used in conjunction with carbon dioxide sensors to help improve the characterization of soil respiration. Typically, soil oxygen sensors use a galvanic cell to produce a current flow that is proportional to the oxygen concentration being measured. These oxygen sensors are buried at various depths to monitor oxygen depletion over time, which is then used to predict soil respiration rates. Apogee oxygen sensors are equipped with a built-in heater to prevent condensation from forming on the permeable membrane, as relative humidity can reach 100 percent in soil.