Continuous in-situ measurements of atmospheric CH4 at the Port-de-Bouc urban-industrial station (south-east of France): a two-year analysis of CH4 spatio-temporal variability and source identification using co-emitted species.

Methane (CH₄) is the second most important direct anthropogenic greenhouse gas after carbon dioxide (CO₂). Its lifetime is 10 times shorter than that of CO₂, and its warming potential 80 times greater over a 20-year period. Reducing methane emissions therefore represents a lever for rapid action on global warming. The Sud-PACA region (south-eastern France), classified by IPCC as a climate "hotspot", is part of these efforts to reduce CH₄ emissions, with the aim of achieving carbon neutrality by 2050. To achieve this, it is essential to reduce the uncertainties of regional CH₄ emissions. Although over 50% of regional methane is estimated to be emitted in the south-western part of the region, there are few CH₄ measurements in this highly urbanized and industrialized area. With a view to filling this gap and better characterizing anthropogenic sources of CH₄, a PICARRO G2401 CRDS analyser and meteorological station were set up in May 2021 as part of the ANR COol-AMmetropolis project at Port-de-Bouc (43°24'7.056''N; 4°58'55.459''E), surrounded by numerous petrochemical industries. This station continuously measures CH₄, CO₂ and CO concentrations to study the variability of these species for the different wind sectors.  The spatio-temporal variability of CH₄ concentration and the identification of its sources using co-emitted species will be presented. All these data represent the first measurements of CH₄ in this industrial area and will also be used to independently verify regional inventories.