<p>To better understand the origins, atmospheric processes and seasonality of atmospheric aerosols in North China, we collected fine aerosols (PM<sub>2.5</sub>) at an urban (Nankai District, ND) and a suburban (Haihe Education Park, HEP) sites in Tianjin from July 2018 to July 2019. The PM<sub>2.5</sub> studied for carbonaceous, nitrogenous and ionic components and stable carbon and nitrogen isotope ratios of total carbon (δ<sup>13</sup>C<sub>TC</sub>) and nitrogen (δ<sup>15</sup>N<sub>TN</sub>). On average, mass concentration of PM<sub>2.5</sub>, organic carbon (OC), elemental carbon (EC) and water-soluble OC (WSOC found to be higher in winter than that in summer at both ND and HEP. SO<sub>4</sub><sup>2−</sup>, NO<sub>3</sub>− and NH<sub>4</sub>+ were dominant ions and accounted for 89 % and 87 % of the total ionic mass at ND and HEP respectively. NO<sub>3</sub>− and NH<sub>4</sub>+ peaked in winter and minimized in summer, whereas SO<sub>4</sub><sup>2−</sup> was higher in summer at both the sites. δ<sup>13</sup>C<sub>TC</sub> and δ<sup>15</sup>N<sub>TN</sub> were −26.5−(−)21.9 ‰ and +1.01−(+)22.8 ‰, respectively, at ND and −25.5−(−)22.8 ‰ and +4.91−(+)18.6 ‰, respectively, at HEP. Based on seasonal variations in the measured parameters, we found that coal and biomass combustion emissions are dominant sources of PM<sub>2.5</sub> in autumn and winter, while biological and/or marine emissions are important in spring and summer in the Tianjin region, North China. In addition, our results implied that the secondary formation pathways of secondary organic aerosols in autumn/winter were different from that in spring/summer, i.e., they were mainly driven by NO<sub>3</sub> radicals in the former period.</p>