Ship plumes in the Baltic Sea Sulfur Emission Control Area: chemical characterization and contribution to coastal aerosol concentrations

Stina Ausmeel,Moa K Sporre,Adam Kristensson,Mårten Spanne,Erik Ahlberg,Axel Eriksson

doi:10.5194/acp-20-9135-2020

Abstract

Abstract. In coastal areas, there is increased concern about emissions from shipping activities and the associated impact on air quality. We have assessed the ship aerosol properties and the contribution to coastal particulate matter (PM) and nitrogen dioxide (NO2) levels by measuring ship plumes in ambient conditions at a site in southern Sweden, within a Sulfur Emission Control Area. Measurements took place during a summer and a winter campaign, 10 km downwind of a major shipping lane. Individual ships showed large variability in contribution to total particle mass, organics, sulfate, and NO2. The average emission contribution of the shipping lane was 29±13 and 37±20 ng m−3 to PM0.5, 18±8 and 34±19 ng m−3 to PM0.15, and 1.21±0.57 and 1.11±0.61 µg m−3 to NO2, during winter and summer, respectively. Sulfate and organics dominated the particle mass and most plumes contained undetectable amounts of equivalent black carbon (eBC). The average eBC contribution was 3.5±1.7 ng m−3 and the absorption Ångström exponent was close to 1. Simulated ageing of the ship aerosols using an oxidation flow reactor showed that on a few occasions, there was an increase in sulfate and organic mass after photochemical processing of the plumes. However, most plumes did not produce measurable amounts of secondary PM upon simulated ageing.

Highlights

Air pollution from shipping is a global concern due to its climate and health effects (Oeder et al, 2015; Brandt et al, 2013; Corbett et al, 2007; Eyring et al, 2010; Lack et al, 2011)
We report the contribution from a major shipping lane to local particle mass concentrations and chemical composition and NO2, as well as the effects of additional ageing simulated with an oxidation flow reactor
This is reflected in the volume concentration (Fig. 2b), which does not increase during all plume events, since the small particles do not contribute greatly to the total volume compared to the background concentrations

Summary

Introduction

Air pollution from shipping is a global concern due to its climate and health effects (Oeder et al, 2015; Brandt et al, 2013; Corbett et al, 2007; Eyring et al, 2010; Lack et al, 2011). The fuel sulfur had been 3.5 % outside SECA but was restricted to 0.5 % in 2020 Ship emission properties, such as particle number and mass concentration, particle size, and chemical composition, depend on a variety of parameters, and ships make up a heterogeneous mix of emission sources. Studies have shown a decrease in mean particle diameter when switching to a lower fuel sulfur content (Betha et al, 2017; Zetterdahl et al, 2016) as well as a decrease in emitted particulate matter (PM) (Lack et al, 2009; Diesch et al, 2013; Mueller et al, 2015; Buffaloe et al, 2014). PM0.15 (ng m−3)b PM0.5 (ng m−3)b NO2 (μg m−3) PN cm−3 (CPC, 4 nm–10 μm)a

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