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An improved method for measuring soil N 2 O fluxes using a quantum cascade laser with a dynamic chamber
Author(s) -
Cowan N. J.,
Famulari D.,
Levy P. E.,
Anderson M.,
Bell M. J.,
Rees R. M.,
Reay D. S.,
Skiba U. M.
Publication year - 2014
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/ejss.12168
Subject(s) - enclosure , cascade , quantum cascade laser , laser , soil water , chemistry , flux (metallurgy) , closure (psychology) , analytical chemistry (journal) , environmental science , materials science , mechanics , soil science , optics , physics , chromatography , telecommunications , organic chemistry , computer science , economics , market economy
Summary A dynamic chamber method was developed to measure fluxes of N 2 O from soils with greater accuracy than previously possible, through the use of a quantum cascade laser ( QCL ). The dynamic method was compared with the conventional static chamber method, where samples are analysed subsequently on a gas chromatograph. Results suggest that the dynamic method is capable of measuring soil N 2 O fluxes with an uncertainty of typically less than 1–2 µg N 2 O‐N m −2 hour −1 (0.24–0.48 g N 2 O‐N ha −1 day −1 ), much less than the conventional static chamber method, because of the greater precision and temporal resolution of the QCL . The continuous record of N 2 O and CO 2 concentration at 1 Hz during chamber closure provides an insight into the effects that enclosure time and the use of different regression methods may introduce when employed with static chamber systems similar in design. Results suggest that long enclosure times can contribute significantly to uncertainty in chamber flux measurements. Non‐linear models are less influenced by effects of long enclosure time, but even these do not always adequately describe the observed concentrations when enclosure time exceeds 10 minutes, especially with large fluxes.