Evaluating Qcl-Based Absorption Spectroscopy Technology for Chamber-Based Flux Measurements of Nitrous Oxide in Agricultural Landscapes.

Nitrous oxide (N₂O) is the largest contributor to the greenhouse gas (GHG) burden of cropping systems in the US, with emissions primarily due to N fertilizer inputs and other soil management activities. Recent advances in fast-response technologies such as laser spectrometry offer exciting new opportunities to investigate the soil–atmosphere exchange of N₂O.

Here we examine the potential for Off-axis Integrated Cavity Output Spectroscopy (OA-ICOS), based on quantum cascade laser (QCL) technology for measuring N₂O fluxes from static chambers in agricultural ecosystems, and compare the technology with the conventional gas chromatography (GC) approach across different chamber designs in multiple agricultural systems at the Kellogg Biological Station in SW Michigan.

In general we found that use of OA-ICOS and GC technologies resulted in very similar estimates of N₂O flux measurement under varying environmental conditions in multiple habitats. Advantages of using OA-ICOS include greater gas detection sensitivity, greater sampling frequency, faster flux collection time (~5 mins vs. 60 mins for GC), multiple gas species capability (e.g., methane, carbon dioxide, water vapor), and a greatly reduced need for labor and consumables (e.g., one person operation, no vials and syringes, no laboratory gas analysis).

The in situ OA-ICOS approach appears to provide an improved method for evaluating gas fluxes from static chambers in the field.