Modelling the Evolution of Maritime Plumes with a Regional Plume-in-Grid Model

As part of the PAREA project, we evaluated the coupling of a Eulerian model, used to model “background” concentrations on a1km² resolution grid, with a Gaussian puff model to better represent the impact of maritime plumes and their chemical evolution close to the port area. By comparing this “plume-in-grid” approach with the classical Eulerian framework, we can quantify the effect of the instantaneous dilution of maritime emissions in the cells on a regional scale. We estimate the latter to be 44.6% for NO_x and 2.1% for BC in the vicinity of the port. This estimation is reinforced by omitting the height emissions from ships in the Eulerian model. The variation also affects the modelling of nitric acid (HNO₃) and particulate nitrate with a maximum effect of 26% further away from the emission sources. The plume-in-grid approach also allows us to better estimate the impact of ship emissions on primary and secondary particles. The results show an increase of 18.5% for NO₂ and 19.1% for NO_x and NO₂ . The impact on SO₂ is small (1.8%) as a result of the low-sulphur emission regulations from 2020. The comparison of the chemical composition of particles in several plumes with observations during peak periods at monitoring stations highlights some discrepancies in the relative contribution of black carbon and organic matter.