Airborne measurement of ship emissions in international waters and Sulphur Emission Control Area

1 January 2020 marked a major change in the legal sulphur content of shipping fuel – from 3.5% to 0.5% by mass outside of the Sulphur Emission Control Areas (SECAs). The anticipated effect of the new regulation is improvement of coastal air quality, supporting both environmental and human health. In addition, since sulphur is believed to be a negative climate forcer, removal of its substantial source might have positive influence on the global climate.
The Atmospheric Composition and Radiative forcing changes due to UN International Ship Emissions regulations (ACRUISE) project demonstrates the use of a large aircraft to measure emissions from ships and their impact on local air quality and cloud formation. The Facility for Airborne Atmospheric Measurements (FAAM) research aircraft was deployed first in July 2019 (before regulation change) in shipping lanes along the Portuguese coast, the English Channel SECA and the Celtic Sea. Over 100 ships were sampled, 15 specifically targeted for plume aging and cloud interaction. A large container ship showed significant reduction in apparent fuel sulphur content upon entering SECA. Bulk statistics in and out of extremely busy shipping lanes were collected. The second, post regulation change, part of the fieldwork was postponed by the COVID-19 pandemic until September 2021. Over 150 ships were measured in the shipping lanes of the Bay of Biscay, the English Channel SECA and Celtic Sea. This part of the work focussed more on targeting specific ships, than on bulk measurements due to lower density of ships in the region and improved sampling strategy.
This study presents a range of aspects of measurements. Onboard measurements of SO₂, CO₂, CH₄ and speciated PM provide emission factors and apparent fuel sulphur content for a variety of ships. Moreover, about 100 whole air samples were taken during each fieldwork and analysed for VOCs. The encountered vessels included container ships, bulk carriers, cruise ships, ferries, crude oil tankers and even elusive LNG tankers. Some ships were measured both in and out of SECA and a few ships were measured both in 2019 and 2021.