Effect of the low sulphur regulations of maritime fuels on ambient air quality: a case study in the Bosphorus strait

The maritime transportation sector poses a significant environmental risk due to its reliance on fossil fuels and its proximity to coastal areas. To address this issue, the International Maritime Organization, authorized by the IPCC, is responsible for reducing and preventing ship-borne emissions. The International Maritime Organization regularly updates emission prevention measures through annual MEPC meetings, particularly under the MARPOL 73/78 Convention, to adapt to changing conditions. In this study, we utilized a bottom-up approach to calculate the emissions of NO_X, SO₂, CO, and PM₁₀ emitted by ships transiting through the Istanbul Bosphorus from 2014 to 2021. We employed the AERMOD air quality dispersion model to generate SO₂ spatial distribution maps, focusing on the year 2014 with the highest pollutant release. The obtained results were compared with measurements from air quality monitoring stations, allowing us to evaluate the contribution of maritime SO₂ emissions to overall Bosphorus pollution. Furthermore, we also examined the impact of low sulfur fuel usage after the sulphur was reduced from 3.5 to 0.5% by mass, in accordance with the regulations put into effect by IMO in 2020.