Local air pollution from oil rig emissions observed during the airborne DACCIWA campaign

Abstract : In the framework of the European DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa) project, the airborne study APSOWA (Atmospheric Pollution from Shipping and Oil platforms of West Africa) was conducted in July 2016 to study oil rig emissions off the Gulf of Guinea. Two flights in the marine boundary layer were focused on the floating production storage and offload-ing (FPSO) vessel operating off the coast of Ghana. Those flights present simultaneous sudden increases in NO₂ and aerosol concentrations. Unlike what can be found in flaring emission inventories, no increase in SO₂ was detected, and an increase in CO is observed only during one of the two flights. Using FLEXPART (FLEXible PARTicle dispersion model) simulations with a regional NO₂ satellite flaring inventory in forward-trajectory mode, our study reproduces the timing of the aircraft NO₂ enhancements. Several sensitivity tests on the flux and the injection height are also performed, leading to the conclusion that a lower NO₂ flux helps in better reproducing the measurements and that the modification of the injection height does not impact the results of the simulations significantly.