Source-oriented characterization of single particles from in-port ship emissions in Guangzhou, China

In this work, we analyzed freshly emitted particles from ship exhaust in the Guangzhou port region before and after the implementation of a clean fuel policy. We used a single particle aerosol mass spectrometer (SPAMS) to measure the changes in the chemical compositions of single particles and evaluate the role of V as a tracer for ship emissions. Particles from high sulfur fuel (S_F) oil (HS) combustion ships consisted of 54.8% elemental carbon-vanadium-sulfate (EC-V-S) and 25.0% vanadium-sulfate (V-S) particles, while particles from low S_F oil (LS) combustion ships were composed of 38.7% organic carbon-sulfate (OC-S) and 28.6% elemental and organic carbon (ECOC) particles. The sulfate-containing particles exhibited a moderate decrease from 95% in HS emissions to 78% in LS emissions, which still suggests the dominant role of sulfate in LS emissions after the implementation of a clean fuel policy. The V-containing particles showed a sharp decrease from 67% in HS emissions to 14% in LS emissions along with the decrease in the relative peak area (RPA) of V, suggesting a remarkable reduction in V in ship exhaust. The count of V-containing particles in urban Guangzhou in June 2017 was generally ten times lower than that in June 2016, which was in accordance with the sharp decrease in V-containing particles in LS emissions rather than in HS emissions. Despite the decrease in V in source-oriented ship emitted particles, the ubiquitous distribution of V in particles from lower S_F combustion ships suggests V is still effective as a tracer of ship emissions in port regions after the implementation of the clean fuel policy. Furthermore, the particles from LS emissions were investigated in comparison to those from gasoline vehicles (GV), diesel vehicles (DV) and coal combustion (CC) sources to better resolve ship-related particles in port regions.