Impact of shipping emission reductions on the chemical composition of aerosols in coastal urban air revealed by receptor modelling and numerical simulations

Abstract

Concerns regarding PM2.5 attributable to the shipping sector, have been highlighted in coastal urban regions due to the well-recognized adverse effects on human health. A number of pollution control strategies have recently been adopted to reduce shipping emissions on both the local and national scales. However, it is difficult to track the effect of these on PM2.5 levels, owing to the non-linear relationship that exists between changes in precursor emissions and PM components. In the present study, an integrated analysis was conducted from various angles with a particular focus on the chemical composition of PM2.5 in the port city of Busan, arising from abatement policies for shipping emissions. Positive Matrix Factorization (PMF) identified that a switch to lower sulphur (S) fuels (from 3.5% to 0.1–0.5%) since January 2020 resulted in considerable annual reductions in shipping-source related surface PM2.5 mass, especially sulphate aerosols. This was seen at a port site (88.9%) as well as at an interior urban background site (81.3%). CMAQ sensitivity analysis showed that the reduction of secondary inorganic aerosols (SIA) further extended to inland areas downwind from ports. In addition, mitigation of secondary organic aerosols (SOA) in coastal urban areas through shipping emission controls, could be anticipated either from the results of receptor modelling applied to two extensive datasets (particulate, gaseous), or from CMAQ simulation results.