Stable Carbon Isotope Compositions and Source Apportionments of Volatile Aromatic Compounds in the Urban Atmosphere of Taiyuan, China

Abstract

This study used Tenax TA absorption tubes to sample volatile aromatic compounds from different emission sources and functional zones in Taiyuan City, Shanxi Province, China. Thermal desorption-gas chromatography-isotope ratio mass spectrometry (TD-GC-IRMS) was subsequently employed to analyze the stable carbon isotope characteristics of the volatile aromatic compounds. The results revealed that the stable carbon isotope ratio (δ13C) of the volatile aromatic compounds emitted through diesel, gasoline, and solvent volatilization, vehicle exhaust, and domestic coal combustion ranged from (-30.79±0.98)‰ to (-29.10±0.14)‰, (-30.96±0.88)‰ to (-28.02±1.77)‰, (-32.13±0.59)‰ to (-27.67±0.49)‰, (-27.58±0.16)‰ to (-25.50±0.75)‰, and (-25.14±0.93)‰ to (-23.44±1.32)‰, respectively. The δ13C value of styrene was (-23.44±1.32)‰, which was only detected in the fumes emitted through domestic coal combustion. Additionally, the sample analysis based on data collected from four different functional zones of Taiyuan City revealed the following:① the δ13C values of the atmospheric volatile aromatic compounds in the mixed residential and traffic zone ranged from (-25.61±2.20)‰ to (-23.91±0.78)‰. Compared with other functional zones, the emissions in this zone were enriched with13C; and ② the δ13C values measured in the industrial zone ranged from (-29.15±1.06)‰ to (-24.53±1.07)‰; the emissions in this functional zone were relatively low in 13C compared with other zones. A comparison of the δ13C values of the atmospheric volatile aromatic compounds and emission sources indicated that the main sources of volatile aromatic compounds at the four sampling points in Taiyuan were vehicle exhausts and domestic coal combustion, while the air sampled in the industrial functional zone was heavily affected by the volatilization of solvents.