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The source of fine particulate matter (PM 2.5 ) has been a longstanding subject of debate, the nitrogen-15 isotope (δ 15 N) has been used to identify the major sources of atmospheric nitrogen. In this study, PM 2.5 samples (n = 361) were collected from September 2017 to August 2018 in the urban area of Guiyang (SW, China), to investigate the chemical composition and potential sources of PM 2.5 . The results showed an average PM 2.5 of 33.0 μg m -3  ± 20.0 μg m -3 . The concentration of PM 2.5 was higher in Winter, lower in Summer. The major water resolved inorganic ions (WSIIs) were Ca 2+ , NH 4 + , Na + , SO 4 2- , NO 3 - , Cl - . Nitrogen-containing aerosols (i.e., NO 3 - and NH 4 + ) suddenly strengthened during the winter, when NO 3 - became the dominant contributor. Over the sampling period, the molar ratio of NH 4 + /(NO 3 - + 2 × SO 4 2- ) ranged from 0.1 to 0.9, thus indicating the full fixation of NH 4 + by existing NO 3 - and SO 4 2- in PM 2.5 . The annual value of NOR was 0.1 while rised to 0.5 in Winter. The variations of NOR (Nitrogen oxidation ratio) (0.1-0.5) values suggest that the secondary formation of NO 3 - occurred every season and was most influential during the winter. The total particulate nitrogen (TN) δ 15 N value of PM 2.5 ranged from -5.9‰ to 25.3‰ over the year with annual mean of +11.8‰ ± 4.7‰, whereas it was between -5.9‰ and 14.3‰ during the winter with mean of 7.0‰ ± 3.8‰. A Bayesian isotope mixing model (Stable Isotope Analysis in R; SIAR) was applied to analyze the nitrogen sources. The modeling results showed that 29%, 21%, and 40% of TN in PM 2.5 during the winter in Guiyang was due to nitrogen-emissions from coal combustion, vehicle exhausts, and biomass burning, respectively. Our results demonstrate that biomass burning was the main contributor to PM during the winter, 80% of the air mass comes from rural areas of Guizhou border, this transport process can increase the risk of particulate pollution in Guiyang., 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 © 2020 Elsevier B.V. All rights reserved.)