title: Evaluation of photoacoustic infrared spectroscopy for simultaneous measurement of N2 O and CO2 gas concentrations and fluxes at the soil surface.
abstract: Simultaneous measurement of N2 O and CO2 flux at the soil surface with photoacoustic infrared spectroscopy (PAS) is gaining popularity due to portability, low maintenance, and ease-of-operation. However, the ability of PAS to measure N2 O with accuracy and precision similar to gas chromatography (GC) is uncertain due to overlap in N2 O, CO2 , and H2 O absorbance spectra combined with the large range in analyte concentrations. We tested the ability of six PAS units to simultaneously measure N2 O and CO2 gas concentrations and fluxes with accuracy and precision similar to two GC units. We also evaluated H2 O vapor and CO2 interferences with N2 O measurement. The accuracy and precision of standard gas concentration measurements with PAS and GC were similar. High water vapor (~26 600 ppm) and CO2 concentrations (~4500 ppm) did not interfere with N2 O measurement across the concentration range typically observed in static flux chambers at the soil surface (~0.5-3.0 ppm N2 O). On average, N2 O fluxes measured with the six PAS were 4.7% higher than one GC and 9.9% lower than the second GC.
authors.affiliation: Department of Agronomy, Iowa State University, Ames, IA 50011, USA. jiqbal.soil@yahoo.com
authors.forename: Javed
authors.initials: J
authors.lastname: Iqbal
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Castellano
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Parkin
mesh_terms: D000162:Acoustics; D002245:Carbon Dioxide / Q000032:analysis*; D002849:Chromatography, Gas; D009609:Nitrous Oxide / Q000032:analysis*; D015203:Reproducibility of Results; D012987:Soil / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods*
chemical_list: D012987:Soil; D002245:Carbon Dioxide; D009609:Nitrous Oxide