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Characterization of carbonaceous aerosols including CC (carbonate carbon), OC (organic carbon), and EC (elemental carbon) were investigated at Xi'an, China, near Asian dust source regions in spring 2002. OC varied between 8.2 and 63.7 μg m-3, while EC ranged between 2.4 and 17.2 μ m-3 during the observation period. OC variations followed a similar pattern to EC and the correlation coeflcient between OC and EC is 0.89 (n=31). The average percentage of total carbon (TC, sum of CC, OC, and EC) in PM2.5 during dust storm (DS) events was 13.6%, which is lower than that during non-dust storm (NDS) periods (22.7%). CC, OC, and EC accounted for 12.9%, 70.7%, and 16.4% of TC during DS events, respectively. The average ratio of OC/EC was 5.0 in DS events and 3.3 in NDS periods. The OC-EC correlation (R2=0.76, n=6) was good in DS events, while it was stronger (R2=0.90, n=25) in NDS periods. The percentage of water-soluble OC (WSOC) in TC accounted for 15.7%, and varied between 13.3% and 22.3% during DS events. The distribution of eight carbon fractions indicated that local emissions such as motor vehicle exhaust were the dominant contributors to carbonaceous particles. During DS events, soil dust dominated the chemical composition, contributing 69% to the PM2.5 mass, followed by organic matter (12.8%), sulfate (4%), EC (2.2%), and chloride (1.6%). Consequently, CC was mainly entrained by Asian dust. However, even in the atmosphere near Asian dust source regions, OC and EC in atmospheric dust were controlled by local emission rather than the transport of Asian dust. 相似文献
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Measurements were performed in spring 2001 and 2002 to determine the characteristics of soil dust in the Chinese desert region of Dunhuang, one of the ground sites of the Asia-Pacific Regional Aerosol Characterization Experiment (ACE-Asia). The mean mass concentrations of total suspended particle matter during the spring of 2001 and 2002 were 317 μg m?3 and 307 μg m?3, respectively. Eleven dust storm events were observed with a mean aerosol concentration of 1095 μg m?3, while the non-dusty days with calm or weak wind speed had a background aerosol loading of 196 μgm?3 on average in the springtime. The main minerals detected in the aerosol samples by X-ray diffraction were illite, kaolinite, chlorite, quartz, feldspar, calcite and dolomite. Gypsum, halite and amphibole were also detected in a few samples. The mineralogical data also show that Asian dust is characterized by a kaolinite to chlorite (K/C) ratio lower than 1 whereas Saharan dust exhibits a K/C ratio larger than 2. Air mass back-trajectory analysis show that three families of pathways are associated with the aerosol particle transport to Dunhuang, but these have similar K/C ratios, which further demonstrates that the mineralogical characteristics of Asian dust are different from African dust. 相似文献
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本文以Node.js、Arc GIS Server和SQL Server为基础,设计了一种前后端语言统一、用于快速开发Web GIS系统的方案,并建立了西安市城市环境气候图信息系统。该系统提供了信息查询及可视化、专题信息表达、空间分析、数据下载、系统留言等服务,可以为城市气候分析和气候图制作工作提供便利。 相似文献
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基于延安市8个区县1997年、2004年和2011年的TM影像数据,运用遥感和地理信息系统软件,对延安地区自退耕还林(草)政策实施以来土地利用动态变化的数量、速度及其空间格局特征进行了定量分析,并结合经济、社会和自然因素数据,通过主成分分析法对延安地区生态脆弱性进行评价。结果表明,1997年至2011年,延安地区的土地利用类型发生了很大变化。耕地面积呈现减少的趋势;居民用地面积处于增长的态势;林地面积增加,并且后期的增加速度明显大于前期;草地面积有小幅度的减少;未利用地和水体面积呈先减少后增加的趋势。生态脆弱性评估表明,在延安地区的8个区县中,北部四县的生态脆弱性指数比南部四县高。在1997年至2011年期间,研究区域内生态环境脆弱性指数逐渐减小,生态环境安全性逐渐增强。 相似文献
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