Carbonyl sulfide mixing ratios, flux measurements and vertical distribution

Carbonyl sulfide (COS) has been proposed as a proxy for carbon dioxide (CO2) taken up by plants at the leaf and ecosystem scales. However, several additional production and removal processes have been identified which could complicate its use at larger scales, among which are soil uptake, dark uptake by plants, and soil and anthropogenic emissions. We have evaluated the significance of these processes at the regional scale through a topdown approach based on atmospheric COS measurements at Gif-sur-Yvette (GIF), a suburban site near Paris (France). Over a period of seven years, hourly measurements at 7 m above ground level were performed by gas chromatography and combined with 222Radon measurements to calculate nocturnal COS fluxes using the Radon-Tracer Method. At the TRN tall tower, atmospheric COS was measured with the Aerodyne Research Quantum Cascade Laser (mini-QCL) formerly deployed at the Saclay (SAC) station [Belviso et al., 2020]. The reader is referred to this publication for more methodological details. The sampling lines, made of Synflex tubing, collected air at 4 heights (5 m, 50 m, 100 m and 180 m) sequentially, the total sequence lasting for 80 minutes.