Characterization, Seasonal Variation, and Source Apportionments of Particulate Amines (PM2.5) in Northern Suburb of Nanjing

Abstract

PM2.5 samples were collected from December 2017 to November 2018 at a northern suburb site of Nanjing. The concentrations of five amines, major water-soluble ions, organic carbon, and elemental carbon were determined. The five amines measured were methylamine, ethylamine, dimethylamine, trimethylamine, and aniline. The annual average of the total amine concentration was (54.2±29.2) ng·m-3. Among these, dimethylamine was the most abundant[annual average:(20.2±13.7) ng·m-3], followed by methylamine[annual average:(13.1±6.3) ng·m-3], trimethylamine[annual average:(8.6±4.1) ng·m-3], ethylamine[annual average:(6.3±4.1) ng·m-3], and aniline[annual average:(5.9±3.9) ng·m-3]. The total amine concentration showed explicit seasonal variations:summer > autumn > spring > winter. The amine concentration on polluted days was higher than that on clean days. This may be influenced by aerosol acidity, promoting the partitioning of gaseous amine into the particulate phase. Aerosol acidity was also the major reason for the higher concentration of amine observed in summer than in other seasons. During new particle formation events, the concentrations of amines increased substantially. Positive matrix factorization (PMF) was utilized to identify the potential sources of amines, identifying six sources:industrial emission, agriculture emission, biomass burning, automobile emission, secondary formation, and dust. Methylamine and ethylamine mainly originated from secondary formation and automobile emissions. Dimethylamine and trimethylamine mainly originated from biomass burning, secondary formation, and automobile emissions; Aniline mainly originated from industrial emissions and biomass burning. A significant seasonal difference is observed with respect to the sources of amines. In spring and autumn, road dust sources account for a relatively high proportion. In summer, secondary sources are the main sources of amines. However, the diurnal variations of amine are not evident, and the secondary source, motor vehicle emission, and biomass combustion are the three main influencing factors.