Seasonal variations of low molecular alkyl amines in PM 2.5 in a North China Plain industrial city: Importance of secondary formation and combustion emissions.

Atmospheric amines have unique acid-neutralizing capacity and play an important role in atmospheric chemical reactions. An integrated observation of PM _2.5 samples (from Dec 2015 to Nov 15, 2016) was conducted in a typical industrial city (Xuzhou), China. Concentrations of total measured amines (∑amines, including methylamine (MA), ethylamine (EA), dimethylamine (DMA), propanamine (PA) and trimethylamine (TMA) + diethylamine (DEA)) were 172.0 ± 98.2 ng m ^-3 , accounting 1.5 ± 0.6 ‰ of PM _2.5 mass. ∑amines were higher in winter (249.0 ± 112.3 ng m ^-3 ) and spring (192.4 ± 75.9 ng m ^-3 ) than in summer (114.7 ± 33.3 ng m ^-3 ) and autumn (103.7 ± 34.3 ng m ^-3 ). Concentrations of MA and EA (the dominant amines) were highest in winter, while DMA, PA and TMA + DEA showed opposite seasonality. EA/MA ratios ranged from 0.04 to 8.7 with a median value of 0.3, and the averaged EA/MA ratio was 2.0 in winter, indicating large contribution of EA. Environmental factors including temperature (T), relative humidity (RH) and atmospheric oxidizing capacity (O ₃ and O _x represented) were found to influence concentrations of amines in PM _2.5 . The Positive Matrix Factorization (PMF) model identified secondary products (41.6 %), combustion emissions (39.8 %), soil and waste incineration emissions (13.2 %) and biological emissions and aging products (5.4 %) as the 4 sources of amines in PM _2.5 . MA was mainly secondary products (82.5 %) and had high contribution of local secondary formation, while EA was mainly derived from combustion emissions (83.7 %) and influenced by regional transportation. In winter, combustion emissions (including coal combustion, biomass burning and traffic emissions, contributed 57.7 %) surpassed secondary products (31.6 %) as the predominant sources of amines, especially under the influence of regional transportation (75.7 %).
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2022 Elsevier B.V. All rights reserved.)