Shipping emissions potentially contribute to the degradation of air quality in port cities. In this study, PM 2.5 samples were collected from two sites at different distances from the shipping channel of Xiamen Port in southeastern China between November 2015 and May 2018 and analyzed for their chemical compositions, which included water-soluble ions, carbonaceous species, and elements. The average annual PM 2.5 mass concentrations were 55.8 ± 22.7 µg m -3 and 56.5 ± 24.5 µg m -3 at the urban and suburban sites, respectively, with the lowest values in summer and the highest in winter/spring. Significantly higher values for vanadium (V) and nickel (Ni) were found at the urban site due to the shorter distance between this location and the shipping channel. Using a PMF model, six source factors were identified: sulfate and shipping emissions (16.6-20.9%), secondary nitrate and chloride (14.7-17.3%), fugitive dust (16.9-23.0%), industrial emissions (5.5-7.0%), primary organic aerosol (14.1-14.8%), and traffic emissions and biomass burning (23.8-24.6%). Potential source contribution function analysis indicated that air masses from the South China Sea contributed significantly to the shipping emissions. The PMF-based method did not distinguish primary shipping emissions from secondary sulfate. When a V-based method was used, the primary PM 2.5 from shipping emissions plus its associated secondary sulfate was shown to contribute 5.5-8.9% of the ambient PM 2.5 on average. The results from the V-based method exhibited strong positive correlations with those of the PMF-based method. Considering the potential negative effect on air quality and the expanding international maritime trade in the long term, our research indicates that policies and regulations for controlling shipping emissions are necessary in all major port cities, including those outside the domestic emission control areas of China.
A B S T R A C T Levoglucosan (LG), water soluble organic carbon (WSOC) and potassium (K '), and the light absorption at 365 nm (Abs 365 ) of the extracted WSOC are measured in PM 2.5 samples collected from November 2011 to July 2013 at four coastal urban sites in southeast China (Fuzhou, Putian, Quanzhou and Xiamen). These species are markers of biomass burning and used to determine the contributions of biomass burning to the PM 2.5 burden in these locations. LG and WSOC concentrations exhibited a clear seasonal pattern, with a large enhancement in winter and spring and a minimum in summer, and annual means across all sites of 59.2946.8 ng m (3 and 2.6991.21 mg C m (3 , respectively. The distinctive seasonal patterns of LG and WSOC are more explained by the East Asian monsoon than the upwind varying emission sources according to the HYSPLIT backward trajectories and MODIS fire spots. Observations produced significant correlation (at the p B0.01 level) between LG and non-sea salt K ' (nss-K ' ) at each site, but the correlations exhibited no clear seasonal trend. The LG/nss-K ' ratios ranged from 0.0390.01 to 0.2490.13 which lay within the limits for the crop residues and/or grass combustion smoke. Stronger correlations were found between WSOC or Abs 365 and sulphate than between WSOC and LG. This observation is consistent with the fact that biomass burning is a less important contributor to WSOC and/or brown carbon than is secondary organic aerosol formation and oxidation. The average relative contributions of biomass burning to OC and WSOC in PM 2.5 were 8.3 and 15.2 %, respectively, estimated by the measured LG to OC and WSOC (LG/OC and LG/WSOC) ratios in comparison to literature-derived LG/OC and LG/WSOC values for biomass burning smoke. Using the reported conversion factor of LG to PM 2.5 for crop straw burning smoke, the LG-estimated PM 2.5 contributions from biomass burning exhibited minimum values in summer and higher values in winter and spring. Positive Matrix Factorisation was used to analyse PM 2.5 sources, and seven major source factors including biomass burning emissions were resolved. The biomass burning sources contributed 3.75Á8.08 % to PM 2.5 mass as an annual average while exhibiting a seasonal variability similar to and higher than those of LG-estimated contributions. These results demonstrate that the contribution from biomass burning smoke to PM 2.5 Á while small Á is non-negligible, especially in the winter and spring sampling periods, that is, northeastern monsoon season.
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