Gas chromatography and photoacoustic spectroscopy for the assessment of soil greenhouse gases emissions

摘要

> face="Verdana, Arial, Helvetica, sans-serif" size="2">Assessments of soil carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) emissions are critical for determination of the agricultural practices' potential to mitigate global warming. This study evaluated the photoacoustic spectroscopy (PAS) for the assessment of soil greenhouse gases (GHG) fluxes in comparison to the standard gas chromatography (GC) method. Two long-term experiments with different tillage and cropping systems over a Paleudult were evaluated using static chambers. PAS measurements of CO₂ and N₂O concentrations showed good relationship and linearity (R₂=0.98 and 0.94, respectively) with GC results. However, CH₄ measurements were significantly affected by air sample moisture which interfered on CH₄ detection by PAS. Overestimation of CO₂ and N₂O concentrations in air samples determined by PAS (14.6 and 18.7%, respectively) were also related to sampling moisture. CO₂ and N₂O fluxes showed good agreement between methods (R₂=0.96 and 0.95, respectively), though PAS overestimated fluxes by 18.6 and 13.6% in relation to GC results, respectively. PAS showed good sensitivity and was able to detect CO₂ and N₂O fluxes as low as 332mg CO₂ m-2 h-1 and 21 size="2">µ face="Verdana, Arial, Helvetica, sans-serif" size="2">g N₂O m-2 h-1. PAS analyzer should be detailed calibrated to reduce humidity interference on CO₂, CH₄ and N₂O concentrations measurements avoiding overestimation or erroneous determination of soil GHG fluxes.