| 上海城区PM2.5中有机碳和元素碳变化特征及来源分析 |
| 摘要点击 4346 全文点击 1710 投稿时间：2014-01-20 修订日期：2014-03-27 |
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| 中文关键词 PM2.5 有机碳 元素碳 来源分析 上海 |
| 英文关键词 PM2.5 organic carbon (OC) elemental carbon (EC) source analysis Shanghai |
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| 中文摘要 |
| 2010年6月~2011年5月间在上海城区点位采集了181组PM2.5样品，采用热光反射法（thermal optical reflectance，TOR）测定了样品中的有机碳（organic carbon，OC）和元素碳（elemental carbon，EC）含量. 结果表明，上海城区环境空气PM2.5中OC和EC年平均浓度分别为8.6 μg ·m-3±6.2 μg ·m-3和2.4 μg ·m-3±1.3 μg ·m-3，两者之和占PM2.5质量浓度的20%. OC和EC的季节平均浓度值冬季最高，夏季最低，秋季OC和EC在PM2.5中的比例最高. 全年OC/EC比值为3.54±1.14. 采用最小OC/EC比值法估算二次有机碳（secondary organic carbon，SOC）含量得到SOC年均浓度为3.9 μg ·m-3±4.2 μg ·m-3，占OC含量的38.9%. 夏季SOC浓度低且与O3最大小时浓度值相关性好，表明光化学反应是夏季SOC的重要生成途径，主导西风向的秋冬季SOC浓度高于静风条件下的浓度水平，存在输送作用. 进一步对OC1、OC2、OC3、OC4、EC1、EC2、EC3和OPC进行主成分分析，结果显示上海城区PM2.5中OC和EC主要来自机动车尾气、燃煤排放、生物质燃烧和道路尘，这4个来源对含碳组分的贡献率达69.8%~81.4%，其中机动车尾气在4个季节中的贡献率均较高，生物质燃烧贡献约15%~20%，春季和秋季道路尘影响明显，冬季燃煤的贡献高于其他季节. |
| 英文摘要 |
| Organic carbon (OC) and elemental carbon (EC) in PM2.5 samples collected in Shanghai urban area during June 2010 to May 2011 were analyzed with IMPROVE-TOR protocol. The results showed that the annual average concentrations of OC and EC in PM2.5 were 8.6 μg ·m-3±6.2 μg ·m-3 and 2.4 μg ·m-3±1.3 μg ·m-3 respectively, accounting for 20% of PM2.5 mass concentration. The seasonal average concentrations of OC and EC were highest in winter and lowest in summer. And the percentages of OC and EC in PM2.5 were highest in autumn. The annual average OC/EC ratio was 3.54±1.14. The concentrations of secondary organic carbon (SOC) were evaluated by the minimum OC/EC ratio method and the annual average concentration of SOC was 3.9 μg ·m-3±4.2 μg ·m-3, accounting for 38.9% of OC. In summer, the concentrations of SOC were relatively low and were correlated well with the maximum hourly concentrations of ozone, which indicated that the photochemical reaction was an important way of SOC formation. In autumn and winter when the west wind direction was predominant, the concentrations of SOC were higher than that in windless condition, which meant the transportation of SOC. The carbonaceous components were associated with source contributions using the principal component analysis (PCA) with eight thermally-derived carbon fractions, OC1, OC2, OC3, OC4, EC1, EC2, EC3 and OPC. Motor vehicle, coal-fired units, biomass burning and road dust were four main sources of OC and EC in PM2.5 in Shanghai urban area, which contributing 69.8%-81.4% of carbonaceous aerosols. The contribution of motor vehicle was high throughout the year. Biomass burning contributed about 15%-20% of OC and EC. The influence of road dust was relatively obvious in spring and autumn. And the contribution of coal-fired units was higher in winter than those in other seasons. |
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