北京夏季典型天气TSP组成和来源对比

The Composition and Sources of TSP of Beijing in Synoptic Processes in Summer Season

于2005年7月选择分别受北方冷空气、海上高压和地方性山谷风影响的3个天气过程条件下,在北京市区和郊区采集了23个大气总悬浮颗粒物（TSP）样品,并采用扫描电镜-X射线能谱技术,根据单颗粒尺度、形貌、特征化学组成解析出各类源对颗粒数浓度的贡献.结果发现：有机/碳质颗粒（占总颗粒数的31.3%,下同）和矿物颗粒（占29.5%）为优势种类,二次源颗粒占10.6%,燃煤飞灰占7.2%,燃煤、机动车排放和建筑施工产生的3类颗粒占4.1%~6.5%.3种天气下颗粒组成特征鲜明,来源差别明显：①冷空气影响下空气质量最好,TSP样品中粒径小于1.0μm和大于5.0μm颗粒较多,一次源处于绝对主导地位（占90%）;②海上高压控制天气下,粒径为1.0-2.5μm的颗粒大幅度增加,有大量的次生粒子生成（占10%-20%）;③地方性天气中颗粒质量浓度偏高,粒径小于1.0μm和1.0-2.5μm颗粒所占比例均较高,但有机/碳质颗粒比例减少,其他次要种类颗粒增多.市区人为源颗粒的种类最多,对郊区影响明显.

In July 2005, 23 total suspended particulate （TSP） samples were collected at 3 sites in Beijing during 3 synoptic processes, namely cold air mass, oceanic high and mountain-valley breezes. The SEM-EDX method was applied to identify sources according to single particle morphology and indicative chemical element（s）, so as to estimate the contribution of each source to particulate number concentration. Results show that the dominated categories are carbonaceous particles （31.3%）, crustal particles （29.5%）, secondary formed S-Ca （ 10.7% ）, fine fly ash （7.2%） from coal burning, and others are from coal burning, vehicle emission and construction （4.1% - 6.5% ）. It was found that the composition characteristics under the three synoptic processes were obvious and their sources were obviously different too. In the case of cold air mass, air quality was the cleanest, the particles less than 1.0μm and greater than 5.0μm were numeric, and over 90% particles were from primary sources; in the case of humid oceanic high, the particles from 1.0 to 2.5 μm increased greatly, and the secondary particles increased dramatically to 10% - 20% ; and in the case of mountain-valley breezes, the particles less than 1.0μm and from 1.0 to 2.5 μm were both numeric, the organic and carbonic particles decreased, and other secondary particles increased. The types of particles from anthropogenic sources are most in number in urban areas, and have significant impacts on suburb areas.