title: Verifying three types of methane fluxes from soils by testing the performance of a novel mobile photoacoustic method versus a well-established gas chromatographic one.
abstract: The performance of a novel portable, tunable diode laser, resonant photoacoustic (TDL-PA) analyzer developed for field measurements of CH4 was compared to a commonly applied offline gas chromatographic (GC) method. This comparative studywas realized under normal field conditions parallel to long-term weekly GC monitoring of four different soil types with very different methane budgets. The method used for gas-exchange measurements was the well-known closed-chamber technique. The TDL-PA analyzer detects methane at 1650.957 nm [R (5) line of the 2v3 band], guaranteeing high precision without the need for correction procedures. The two techniques correlated well (R2 = 0.988) over the entire concentration range (0.15-33 ppmv CH4) tested at highly varying flux rates between -30 and -12 ppbv CH4 min(-1) for uptakes and between 2.5 and 362 ppbv CH4 min(-1) for emissions. The two analyzers proved to be interchangeable, leaving the online advantages to the TDL-PA. A suitable CH4 online GC solution for chamber measurement is not available as a portable system. Additionally, the data sampling rate of 2 Hz enables a direct coupling to other infrared gas analyzers with the high time resolution commonly required to determine plant CO2 assimilation rates or soil respiration rates.
authors.affiliation: Plant Ecology, Albrecht-von-Haller-Institute for Plant Sciences, University of Göttingen, Untere Karspile 2, D-37073 Göttingen, Germany. hermann.jungkunst@biologie.uni-goettingen.de
authors.forename: Hermann F
authors.initials: HF
authors.lastname: Jungkunst
authors.forename: Raimund
authors.initials: R
authors.lastname: Sauter
authors.forename: Andreas
authors.initials: A
authors.lastname: Link
authors.forename: Sabine
authors.initials: S
authors.lastname: Fiedler
authors.forename: Karl
authors.initials: K
authors.lastname: Stahr
authors.forename: Ulrich
authors.initials: U
authors.lastname: Haas
mesh_terms: D002849:Chromatography, Gas / Q000295:instrumentation / Q000379:methods*; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods*; D008697:Methane / Q000032:analysis*; D015203:Reproducibility of Results; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis*
chemical_list: D012987:Soil; D012989:Soil Pollutants; D008697:Methane