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.
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.
Jungkunst
Hermann F
HF
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
Sauter
Raimund
R
Link
Andreas
A
Fiedler
Sabine
S
Stahr
Karl
K
Haas
Ulrich
U
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*
D012987:Soil; D012989:Soil Pollutants; D008697:Methane