Sulphur dioxide downwind of ports after the 2020 global sulphur cap and the 2025 Mediterranean emission control area
2020 küresel kükürt sınırı ve 2025 Akdeniz emisyon kontrol alanından sonra limanların rüzgâr altında kükürt dioksit
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Abstract
Since 1 May 2025 ships in the Mediterranean Sea must use fuel with at most 0.10% sulphur. Model studies made before the decision projected lower sulphur dioxide (SO₂) in coastal cities, but no assessment based on measurements made after the rule took effect is available. We combined hourly SO₂ from the European air quality reporting system for 2016–2026 with hourly winds from nearby meteorological stations at 330 sampling points located within 5 km of 154 ports, and computed for each point and month the port-sector excess: mean SO₂ when the wind blows from the port minus the mean when it blows from the opposite sectors. At Mediterranean monitors the excess fell from 1.45 µg m⁻³ in 2016 to 0.88 in 2019 and 0.35 in 2020, the year the global 0.50% cap began, and stood at 0.40 in 2024. After the emission control area it was 0.33 in 2025 and 0.30 in 2026. Relative to ports in the North Sea and Baltic, where the limit did not change, the change after May 2025 was -0.11 µg m⁻³ (95% confidence interval -0.54 to 0.31), against -0.57 (-1.28 to 0.14) for the 2020 cap. A comparison of mean concentrations at port and inland monitors, the design most often used for such evaluations, returned no effect for 2025 and for 2020 an apparent effect confined to industrial sites in one country. Little ship-related SO₂ remained to be removed at the monitors by 2025, and the fixed network can only bound the effect of the new limit at about half a microgram per cubic metre.
Keywords
Ship emissions; Sulphur dioxide; Emission control area; Mediterranean Sea; IMO 2020; Wind-sector analysis
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