[Pollution Characteristics and Source Analysis of Carbon and Nitrogen Components in Ambient PM_2.5 in Huangshi City]

Based on stable isotope technology and a PMF model, the pollution characteristics and sources of carbon and nitrogen components in ambient PM_2.5 in Huangshi City were explored. The results showed that the total carbon concentration[ρ(TC)] and the total carbon isotopic composition (δ¹³C_TC) in ambient PM_2.5 in Huangshi City both showed seasonal variation characteristics of being high in winter and low in summer, with values of (4.4±1.2) μg·m^-3 and (-26.3±0.5)‰ in summer and (9.9±3.5) μg·m^-3 and (-25.5±0.5)‰ in winter, respectively. The total nitrogen concentration[ρ(TN)]was significantly lower in summer[(9.1±9.1) μg·m^-3]than that in winter[(62.4±26.4) μg·m^-3], whereas the total nitrogen isotopic composition (δ¹⁵N_TN) was obviously enriched in summer[(12.8±1.9)‰]compared with that in winter[(2.9±4.0)‰]. In addition to the contribution from local sources, the carbon and nitrogen components were mainly affected by the short-range regional emission in northern Hunan and the long-distance transport in the northwest. The MixSIAR model and the PMF model indicated that the vehicle emission source was the main source of carbon components in PM_2.5, with contribution rates of 38.9% and 39.3%, respectively. MixSIAR results showed that NO emission sources had a greater impact on nitrogen components in PM_2.5 of different seasons than NH₃ emission sources, and their contribution was higher in summer (80%) than that in winter (66.8%), among which the NO emissions from coal combustion (summer:36.1%; winter:20.2%) had the largest contribution. By contrast, the PMF model indicated that the main source of nitrogen components was vehicle emissions (59.8%). Combining multiple models to overcome the uncertainty and subjectivity of single-model analysis can provide a theoretical basis for actively controlling and reducing fine particulate matter emissions and effectively dealing with urban aerosol pollution.