Location: Soil, Water & Air Resources ResearchTitle: Portable automation of static chamber sample collection for quantifying soil gas flux
|DAVIS, MORGAN - Iowa State University|
|GROH, TYLER - Iowa State University|
|WILLIAMS, RYAN - Iowa State University|
|ISENHART, THOMAS - Iowa State University|
|HOFMOCKEL, KIRSTEN - Pacific Northwest National Laboratory|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2018
Publication Date: 2/8/2018
Publication URL: https://handle.nal.usda.gov/10113/6472257
Citation: Davis, M.P., Groh, T.A., Parkin, T.B., Williams, R.J., Isenhart, T.M., Hofmockel, K.H. 2018. Portable automation of static chamber sample collection for quantifying soil gas flux. Journal of Environmental Quality. 47(2):270-275. https://doi.org/10.2134/jeq2017.10.0387.
Interpretive Summary: Agricultural soils are a major source of the greenhouse gas emissions to the atmosphere. Because of their transient nature, soil greenhouse gas emissions are difficult to quantify. The measurements are required at many times during the year, and are labor intensive. In this work we developed an instrument that will automatically collect gas samples for greenhouse gas emissions measurements. The precision and accuracy of this instrument was found to be equal to or better than manual methods. We estimate that this automated instrument will decrease cost of soil greenhouse gas emissions measurements by a factor of 4, compared to manual methods, and will benefit scientists performing such work.
Technical Abstract: The collection of soil gas flux using the static chamber method is labor intensive. The number of chambers that can be sampled in a given time period is limited by the spacing between chambers and the availability of trained research technicians. However, the static chamber method can limit spatial and temporal variation and allow for the analysis of multiple gases from a single sample. The chamber automated sampling equipment (FluxCASE) for measuring soil gas flux was designed to collect and store samples at assigned time points. Eliminating the return to each chamber at multiple time points allows a single technician to sample all of the chambers deployed in an experiment simultaneously. The objectives of this study were to examine the accuracy and precision of the FluxCASE system. To meet these objectives, FluxCASEs were tested in the laboratory and field. Coefficients of variation of FluxCASE samples for nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) concentrations were all comparable to manual samples collected from a standardized gas mixture. Soil gas fluxes measured from FluxCASEs were also in agreement with manual sampling for both N2O (r2 = 0.946) and CO2 (r2 = 0.930). The FluxCASE system was also found to be precise, with low variability between FluxCASEs and across a range of soil gas fluxes. Implementing the FluxCASE system is an alternative to improve the efficiency and accuracy of the static chamber method for measuring soil gas flux while maintaining the accuracy and precision of manual sampling.