| Summary: | To characterize seasonal carbonaceous aerosol pollution in Taiyuan, a typical city in North China that mainly relies heavily on coal, a total of 124 PM<sub>2.5</sub> samples were collected from August 2018 to the next May. The annual mean PM<sub>2.5</sub> concentration was 83.8 ± 48.5 μg m<sup>−3</sup>, with a seasonal rank of winter (117.4 ± 47.6 μg m<sup>−3</sup>) > spring (79.2 ± 34.3 μg m<sup>−3</sup>) > fall (67.3 ± 34.7 μg m<sup>−3</sup>) > summer (31.8 ± 6.5 μg m<sup>−3</sup>), suggesting that fine particulate pollution was still serious in cold seasons. Organic carbon (OC) and elemental carbon (EC) showed similar seasonal patterns with PM<sub>2.5</sub>. The mean concentration values of OC in summer, fall, winter, and spring were 5.1 ± 0.9, 11.8 ± 6.4, 22.1 ± 14.9, and 12.2 ± 6.7 μg m<sup>−3</sup>, respectively. The mean concentration values of EC in summer, fall, winter, and spring were 1.5 ± 0.3, 2.5 ± 1.6, 4.4 ± 2.8, and 2.4 ± 1.5 μg m<sup>−3</sup>, respectively. The proportion of total carbon aerosol (TCA) was about 31.7%, 33.8%, 30.0%, and 27.0% in PM<sub>2.5</sub> in summer, fall, winter, and spring, respectively. The good correlation between OC vs. EC and the high value of OC/EC suggests that coal and biomass combustion were the main emissions in cold seasons, aggravated by adverse meteorological conditions and the dustpan-shaped terrain. The mean annual secondary organic carbon (SOC) concentration was 6.1 ± 7.1μg m<sup>−3</sup>, representing 38.7% of the OC content. The present results presented the serious carbonaceous particulate pollution, which might affect haze pollution in cold seasons.
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