A compact spectroscopic analyzer for simultaneous measurement of N2O, CH4, and CO2 fluxes from soils

Abstract

Nitrous oxide (N₂O), methane (CH₄), and carbon dioxide (CO₂) are three major greenhouse gases (GHG), contributing more than 90% of global warming effects. Across land ecosystems, the source and sink patterns of these GHGs exhibit significant spatial and temporal variability. Field measurements of soil-atmosphere exchange fluxes provide valuable evidence for understanding local GHG dynamics and serve as a complement to comprehensive GHG assessments. While a lot of laboratory-based instruments can facilitate the determination of all three GHGs, few commercially available devices balance precision and portability for in situ flux measurements in remote regions. Here, we present a newly developed GHG analyzer (HT8850) based on a dual-laser spectroscopic system, which determines N₂O, CH₄, CO₂ and H₂O concurrently. With a size of 47 cm * 36 cm * 18 cm, a weight of 14.8 kg, and a power consumption below 100 W, this instrument maintains a good balance between portability/budget and precision/stability. With standard gas measurements in the laboratory, we found that the HT8850 has reasonable accuracy and fast response with an inflow rate of 0.5 L min^-1. Based on the Allan deviation analysis, the 1σ-detection limits under static operation are 1.11 ppb, 2.38 ppb, 0.39 ppm and 6.95 ppm for N₂O, CH₄, CO₂ and H₂O measurements with a 10-second averaging time, respectively. In field application with the soil flux chamber, the analyzer demonstrated good potential in quantifying fluxes for the soil-atmosphere exchange of all three GHGs. Therefore, this compact and integrated spectroscopic analyzer offers a versatile solution for scientists interested in field flux measurements, likely contributing to the further development of in situ applications for GHG flux measurements.