Journal cover Journal topic
Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

Journal metrics

  • IF value: 3.089 IF 3.089
  • IF 5-year<br/> value: 3.700 IF 5-year
    3.700
  • CiteScore<br/> value: 3.59 CiteScore
    3.59
  • SNIP value: 1.273 SNIP 1.273
  • SJR value: 2.026 SJR 2.026
  • IPP value: 3.082 IPP 3.082
  • h5-index value: 45 h5-index 45
Atmos. Meas. Tech., 10, 1259-1267, 2017
https://doi.org/10.5194/amt-10-1259-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
30 Mar 2017
An eddy-covariance system with an innovative vortex intake for measuring carbon dioxide and water fluxes of ecosystems
Jingyong Ma1,2, Tianshan Zha1,2, Xin Jia1,2, Steve Sargent3, Rex Burgon3, Charles P.-A. Bourque4, Xinhua Zhou3, Peng Liu1,2, Yujie Bai1,2, and Yajuan Wu1,2 1School of Soil and Water Conservation, Beijing Forestry University, Beijing, China
2Beijing Engineering Research Center of Soil and Water Conservation, Beijing Forestry University, Beijing, China
3Campbell Scientific, Inc., Logan UT, USA
4Faculty of Forestry and Environmental Management, 28 Dineen Drive, University of New Brunswick, Fredericton, New Brunswick, Canada
Abstract. Closed-path eddy-covariance (EC) systems are used to monitor exchanges of trace gases (e.g., carbon dioxide [CO2], water vapor [H2O], nitrous oxide and methane) between the atmosphere and biosphere. Traditional EC-intake systems are equipped with inline filters to prevent airborne dust particulate from contaminating the optical windows of the sample cell which causes measurement degradation. The inline filter should have a fine pore size (1 to 20 µm is common) to adequately protect the optics and a large filtration surface area to extend the time before it clogs. However, the filter must also have minimal internal volume to preserve good frequency response. This paper reports test results of the field performance of an EC system (EC155, Campbell Scientific, Inc., Logan Utah, USA) with a prototype vortex intake replacing the inline filter of a traditional EC system. The vortex-intake design is based on fluid dynamics theory. An air sample is drawn into the vortex chamber, where it spins in a vortex flow. The initially homogenous flow is separated when particle momentum forces heavier particles to the periphery of the chamber, leaving a much cleaner airstream at the center. Clean air (75 % of total flow) is drawn from the center of the vortex chamber, through a tube, to the sample cell where it is exposed to the optical windows of the gas analyzer. The remaining 25 % of the flow carries the heavier dust particles away through a separate bypass tube. An EC155 system measured CO2 and H2O fluxes in two urban-forest ecosystems in the megalopolis of Beijing, China. These sites present a challenge for EC measurements because of the generally poor air quality which has high concentrations of suspended particulate. The closed-path EC system with vortex intake significantly reduced maintenance requirements by preserving optical signal strength and sample-cell pressure within acceptable ranges for much longer periods. The system with vortex intake also maintained an excellent frequency response. For example, at the Badaling site, the amount of system downtime attributed solely to clogged filters was reduced from 26 % with traditional inline filters to 0 % with the prototype vortex intake. The use of a vortex intake could extend the geographical applicability of the EC technique in ecology and allow investigators to acquire more accurate and continuous measurements of trace-gas fluxes in a wider range of ecosystems.

Citation: Ma, J., Zha, T., Jia, X., Sargent, S., Burgon, R., Bourque, C. P.-A., Zhou, X., Liu, P., Bai, Y., and Wu, Y.: An eddy-covariance system with an innovative vortex intake for measuring carbon dioxide and water fluxes of ecosystems, Atmos. Meas. Tech., 10, 1259-1267, https://doi.org/10.5194/amt-10-1259-2017, 2017.
Publications Copernicus
Download
Short summary
The vortex intake significantly reduced maintenance requirements and downtime for a closed-path eddy-covariance system compared to the original inline filter design. Vortex intake kept the sample cell windows cleaner, preserving the optical signal strength of CO2 longer. Its installation also avoided the need for an inline filter in the sample path, sustaining an acceptable sample cell differential pressure over a much longer period. There was no significant attenuation of high frequencies.
The vortex intake significantly reduced maintenance requirements and downtime for a closed-path...
Share