Temporal variations in aerosol composition at Lanzhou City, Northwestern China

查看全文 作　　者：Feng She YiFan Cheng ShiGong Wang YongTao Guo JinYan Wang MinJing Ma KeZheng [1]Shang

机构地区：[1]Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China

出　　处：《Research in Cold and Arid Regions》索引2011年第3卷第3期,共12页

基　　金：supported by the National Special Project for Commonweal Industry in China (GYHY201106034);the National Support Project for Science and Technology of China (2007BAC29B03; 2009BAC53B02);the Project of National Natural Science Foundation of China(41075103) 摘　　要：Although Lanzhou is one of the most heavily polluted cities in China, the composition of its air pollutants have not yet been stud- ied in detail. The data of four months on the concentrations and compositions of ions from daily air-filter samples in the winter and spring during 2007-2008 were analyzed to investigate temporal trends and their possible causes. The results indicate that mean concentrations of almost all the aerosol components are greater in winter than in spring due to stronger emissions in winter and weaker localized dispersion. Spring dust storms are the major cause of the highest peak PM10 concentrations recorded during the study period; however, these elevated levels were transient. Ion concentrations related to coal combustion show the greatest reduc- tion from winter to spring, while the concentrations of strong crustal components show a less-pronounced reduction. Strong cycles in the levels of particulate matter (PM) and all ions are also observed during the winter months due to meteorological conditions. Depending on the season, nine different ions accounted for 20%-50% of the PM concentration. The particle size of polluting ions was constant at times of increasing PM concentrations (particularly during winter), whereas the particle size of crustal ions in- creased dramatically during spring dust storms. Local meteorological conditions (especially wind speed) have a strong influence on the levels of pollutants. Four dust storms were noted, including one during winter. In summary, the regional transport of desert dust from the Gobi can significantly affect air quality and the chemical composition of aerosols in Lanzhou. The dust storms can strongly increase concentration of crustal ions, which are characteristics of deserts in northwestern China. This observation is in agreement with back-trajectories, which show reduced levels of pollutant ions during dust storms. Data on nitrate:sulfate ratios in- dicate that stationary point sources are the main source of ions rather than mobile sources. 关键词：中国西北气溶胶兰州市时空变化组成空气污染物离子浓度颗粒物浓度

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Temporal variations in aerosol composition at Lanzhou City, Northwestern China

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