Abstract
Commercial shipping is considered as an important source of air pollution and cloud condensation nuclei (CCN). To assess the climatic and environmental impacts of shipping, detailed characterization of ship plumes near the point of emission and understanding of ship plume evolution further downwind are essential. This airborne measurement study presents the online characterization of particulate phase ship emissions in the region of Western Europe in 2019 prior to new international sulfur emission controls becoming enacted. More than 30 ships from both the sulfur emission control area (SECA) in the English Channel and the open sea (OS) are measured and compared. Ships within the SECA emitted much less sulfate (SO4) compared with those at OS. When shifted to a lower apparent fuel sulfur content (FSC) at similar engine loads, the peak of the fresh ship emitting the particle number size distribution shifted from around 60-80 nm in diameter to below 40 nm in diameter. The emission factors (EFs) of sulfate are predicted to decrease by around 94% after the 2020 regulation on ship sulfur emission in the open ocean. The EFs of refractory black carbon (rBC) and organic compounds (Org) do not appear to be directly affected by the lower sulfur contents. The total number concentration for condensation nuclei (CN) >2.5 nm and >0.1 μm are predicated to be reduced by 69 and 56%, respectively. Measured plume evolution results indicate that the S(IV) to S(VI) conversion rate was around 23.4% per hour at the beginning of plume evolution, and the CCN and CN >2.5 nm ratio increased with plume age primarily due to condensation and coagulation. We estimate that the new sulfur emission regulation will lead to a reduction of more than 80% in CCN from fresh ship emissions. The ship-emitted EFs results presented here will also inform emission inventories, policymaking, climate, and human health studies.
Highlights
With the growth of the international seaborne trade in recent decades, commercial shipping emissions have become an important anthropogenic air pollution source.[1,2] As heavy fuel oil (HFO) with a high sulfur content was one of the dominant shipping fuel types before 2020, commercial shipping had until recently been an ever increasing source of sulfur emissions.[3]
Sulfate derived from shipping emission is a major source of cloud condensation nuclei (CCN).[4]
The European coastal regions are among the busiest maritime transport regions globally, where commercial shipping has been estimated to contribute more than 11% of the observed PM1.9
Summary
With the growth of the international seaborne trade in recent decades, commercial shipping emissions have become an important anthropogenic air pollution source.[1,2] As heavy fuel oil (HFO) with a high sulfur content was one of the dominant shipping fuel types before 2020, commercial shipping had until recently been an ever increasing source of sulfur emissions.[3]. Human health is significantly influenced by ship emissions,[6,7] and shiprelated particulate matter emissions may increase lung cancer deaths.[8] The European coastal regions are among the busiest maritime transport regions globally, where commercial shipping has been estimated to contribute more than 11% of the observed PM1 (particulate matter with an aerodynamic diameter of less than 1 μm).[9]. To reduce the health and ecosystem impacts of commercial shipping, the International Maritime Organization (IMO) set a series of increasingly tighter regulations regarding ship-emitted pollutants. From January 2020, the global cap of the FSC of marine fuels was further reduced to less than 0.5%. Received: June 20, 2020 Revised: November 8, 2020 Accepted: November 9, 2020 Published: November 18, 2020
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