A new open-path eddy covariance method for nitrous oxide and other trace gases that minimizes temperature corrections.

Autor: Pan D; Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey, USA.; Center for Mid-Infrared Technologies for Health and the Environmental, NSF-ERC, Princeton, New Jersey, USA., Gelfand I; Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan, USA.; W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, USA.; The French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, Israel., Tao L; Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey, USA.; Center for Mid-Infrared Technologies for Health and the Environmental, NSF-ERC, Princeton, New Jersey, USA., Abraha M; Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan, USA.; W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, USA.; Center for Global Change and Earth Observations, Michigan State University, East Lansing, Michigan, USA., Sun K; Department of Civil, Structural and Environmental Engineering, University at Buffalo, Buffalo, New York, USA.; Research and Education in eNergy, Environment and Water (RENEW) Institute, University at Buffalo, Buffalo, New York, USA., Guo X; Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey, USA.; Center for Mid-Infrared Technologies for Health and the Environmental, NSF-ERC, Princeton, New Jersey, USA., Chen J; Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan, USA.; Center for Global Change and Earth Observations, Michigan State University, East Lansing, Michigan, USA., Robertson GP; Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan, USA.; W.K. Kellogg Biological Station, Michigan State University, Hickory Corners, Michigan, USA.; Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, Michigan, USA., Zondlo MA; Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey, USA.; Center for Mid-Infrared Technologies for Health and the Environmental, NSF-ERC, Princeton, New Jersey, USA.
Jazyk: angličtina
Zdroj: Global change biology [Glob Chang Biol] 2022 Feb; Vol. 28 (4), pp. 1446-1457. Date of Electronic Publication: 2021 Dec 03.
DOI: 10.1111/gcb.15986
Abstrakt: Low-power, open-path gas sensors enable eddy covariance (EC) flux measurements in remote areas without line power. However, open-path flux measurements are sensitive to fluctuations in air temperature, pressure, and humidity. Laser-based, open-path sensors with the needed sensitivity for trace gases like methane (CH 4 ) and nitrous oxide (N 2 O) are impacted by additional spectroscopic effects. Corrections for these effects, especially those related to temperature fluctuations, often exceed the flux of gases, leading to large uncertainties in the associated fluxes. For example, the density and spectroscopic corrections arising from temperature fluctuations can be one or two orders of magnitude greater than background N 2 O fluxes. Consequently, measuring background fluxes with laser-based, open-path sensors is extremely challenging, particularly for N 2 O and gases with similar high-precision requirements. We demonstrate a new laser-based, open-path N 2 O sensor and a general approach applicable to other gases that minimizes temperature-related corrections for EC flux measurements. The method identifies absorption lines with spectroscopic effects in the opposite direction of density effects from temperature and, thus, density and spectroscopic effects nearly cancel one another. The new open-path N 2 O sensor was tested at a corn (Zea mays L.) field in Southwestern Michigan, United States. The sensor had an optimal precision of 0.1 ppbv at 10 Hz and power consumption of 50 W. Field trials showed that temperature-related corrections were 6% of density corrections, reducing EC random errors by 20-fold compared to previously examined lines. Measured open-path N 2 O EC fluxes showed excellent agreement with those made with static chambers (m = 1.0 ± 0.3; r 2  = .96). More generally, we identified absorption lines for CO 2 and CH 4  flux measurements that can reduce the temperature-related corrections by 10-100 times compared to existing open-path sensors. The proposed method provides a new direction for future open-path sensors, facilitating the expansion of accurate EC flux measurements.
(© 2021 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)
Databáze: MEDLINE
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