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We developed an innovative tool to quantify CO2 and CH4 emissions at the scale of an industrial site, based on a mass balance approach relying on a newly developed light-weight (1.4 kg) open path laser absorption spectrometer operable on-board Unmanned Aircraft Vehicles (UAVs). This spectrometer simultaneously records in situ CO2 and CH4 concentrations at high frequency (24 Hz in this study) with precisions of 10 ppb for CH4 and 1 ppm for CO2 averaged at 1 Hz. The large range of measurable concentrations, up to 1000 ppm for CO2 and 200 ppm for CH4, makes this analyzer suitable for operation on industrial sites at a short distance from the emission sources, therefore avoiding many logistical and legal limits associated with most long-range airborne observations. To quantify the emissions, high spatial resolution atmospheric concentration measurements obtained throughout a plume cross-section downwind of a source within the limited UAV flight period are exploited by calculations using a mass balance approach. This high spatial resolution, allowed by the high acquisition frequency, limits the use of horizontal interpolation, thus gaining in precision compared to current airborne alternative quantification techniques. A field validation campaign, conducted on the TotalEnergies TADI test platform at Lacq, France, consisted in controlled CO2 and CH4 leak experiments to which several institutes participated with various measurement systems (gas LiDAR, multispectral camera, infrared camera including concentrations and emissions quantification system, acoustic sensors, ground mobile and fixed Cavity RingDown Spectrometers). Our method was proved suitable to detect leaks during controlled release experiments with emission fluxes down to 0.01 g s-1, with 24 % of estimated CH4 fluxes within the -20 % to +20 % error range, 80 % of quantifications within the 50 % to +100 % error range and all of our results within the -69 % to +150 % error range. Such precision levels are better ranked than current top-down alternative techniques to quantify CH4 at comparable spatial scales. Observations across the plume of two offshore oil and gas platforms operated by TotalEnergies in the North Sea were used to quantify the instantaneous greenhouse gases emissions of these facilities and are coherent with reference emissions for these platforms estimated by mass balance and combustion calculations for CO2. The operational deployment of such instruments and quantification methods, on a large scale and on a regular basis, potentially with fully autonomous UAVs, will allow the quantification of the time dependent greenhouse gases emissions of numerous oil and gas facilities. [ABSTRACT FROM AUTHOR]

Both laboratory and field experiments were carried out in order to define suitable configuration ranges for the gas sampling systems (GSSs) of infrared gas analyzers (IRGAs) used in eddy covariance measurements. In the laboratory, an original dynamic calibration bench was developed in order to test the frequency attenuation and pressure drop generated by filters. In the field, three IRGAs of the same type equipped with different filters or different rain caps were installed and run and the real frequency response of the complete setup was tested. The main results are as follows. - Filters may have a strong impact on the pressure drop in the GSS and this impact increases with flow rate. - Conversely, no impact of the tested filters on cut-off frequency was found, GSSs with and without filters presenting similar cut-off frequencies. - The main limiting factor of cut-off frequency in the field was found to be the rain cap design. In addition, the impact of this design on pressure drop was also found to be noteworthy. [ABSTRACT FROM AUTHOR]