10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Chemical Composition and Seasonal Variation of PM2.5 in Urban and Rural Regions of the Guanzhong Basin, Northwestern China
JIN LI, Gehui Wang, Jianjun Li, Institute of Earth Environment, CAS
Abstract Number: 638 Working Group: Aerosol Chemistry
Abstract In order to investigate the character of regional air pollution in the Guanzhong Basin, one of the most polluted areas of China, PM2.5 samples were collected at Xi’an in July 2016 and a rural site around 100 km northeast of Xi’an in August 2016 and January 2017, and determined for organic carbon (OC), elemental carbon (EC), and inorganic ions. The concentration of PM2.5 in summer was 48.88±22.69 μg·m-3 and 62.60±14.23 μg·m-3 in urban and rural areas, respectively, and increased to 161.79±87.05 μg·m-3 in winter in the rural region. At the rural site, concentrations of OC and EC (41.61±22.03 μg·m-3 and 12.31±5.51 μg·m-3) in winter were significantly higher than those in summer (6.75±1.81 μg·m-3 and 3.80±2.27 μg·m-3), with no significant differences between daytime and nighttime. The correlation of OC and EC was strong (R2=0.92) in winter, and much weaker (R2=0.61) in summer, suggesting an enhanced formation of secondary organic aerosols in summer due to the higher temperature and stronger solar radiation. The water-soluble inorganic ions (WSIIs) accounted for 41% and 48% of PM2.5 in urban and rural areas during summer, and 41% in the rural area during winter. Secondary inorganic aerosols (SO42−, NO3−, and NH4+) were dominant WSIIs, accounting for 78-91% of total WSIIs. Contributions of SO42−, NH4+, and K+ to PM2.5 in the rural area were much higher than those in the urban area, indicating the impact of rural agricultural ammonia emissions and biomass burning. In contrast, the higher contribution of NO3- and lower SO42-/NO3- ratio (8.37±5.31 and 2.14±1.32 in rural and urban areas in summer) suggested a more important emission from vehicle exhaust in the urban area. Our results presented detailed information about chemical composition and source contribution of PM2.5 in the Guanzhong region and may be helpful for the government to make effective control and management.