【摘要】 为掌握太原市冬季灰霾发生期间黑碳气溶胶形貌特征和化学成分变化特点,分别于2011-12-30T08:00至2012-01-01 T 04:00和2018-11-25 T 08:00至2018-11-27 T 04:00灰霾发生期间在山西大学环境与资源学院楼顶使用MAY七级冲击式颗粒采样器每隔4h采集空气动力学直径分别为0.25～0.5μm、0.5～1.0μm以及1～2μm的大气单颗粒分析样品,运用带超薄窗口能谱仪的扫描电镜(JEOL JSM-6390)测定了样品中4330个颗粒的二次电子像及X射线能谱,通过基于蒙特卡罗模拟程序的定量电子探针微区分析技术对每个颗粒的元素原子浓度进行了计算,并对颗粒进行了分类与计数。共检测到6类颗粒,分别是矿物尘、碳质颗粒、钠盐颗粒、二次颗粒、富铁颗粒和其他,其中黑碳气溶胶数量相对丰度在2011和2018年样品中平均为26.8%和34.2%。按照伸长率(E)、纵横比(R)、是否与其他物质结合等将其分为伸展型、支链型、嵌入或粘附型和团聚型4种,反映了黑碳颗粒不同的老化过程。2011年样品中团聚型和支链型数量较多,而2018年样品中伸展型和嵌入型多于团聚型和支链型,提示2011年黑碳气溶胶老化程度大于2018年,与灰霾严重程度相一致。本研究表明,与2011年相比,太原市2018年冬季灰霾污染特征和燃料结构可能发生了较大改变。更多还原

【Abstract】 This study aims to investigate the modifications of atmospheric black carbon aerosols in morphological characteristics and chemical compositions during wintertime haze events in urban Taiyuan, Shanxi Province, China. Using a seven-stage MAY cascade impactor, individual atmospheric particles in the aerodynamic diameter ranges of 1.0–2.0 μm, 0.5–1.0 μm, and 0.25–0.5 μm were collected on stages 4, 5, and 6, respectively, at every 4 h from 2011-12-30 08: 00 am to 2012-01-01 4: 00 am and from 2018-11-25 08: 00 am to 2018-11-27 04: 00 am on the roof of a fifth-floor building at the College of Environment and Resource Science, Shanxi University(located in Taiyuan City) when haze episodes occurred. The secondary electron images and X-ray spectra of 4330 particles were determined using a scanning electron microscopy equipped with an ultrathin-window energy dispersive X-ray spectrometer(JEOL JSM-6390). The elemental atomic concentrations in each particle were calculated with a Monte Carlo simulation program based on the quantitative electron probe X-ray microanalysis. Subsequently, the particles were classified based on their chemical composition, and the number of every type of particles was counted. Overall, six groups of particles were identified, including mineral dust, carbonaceous, sodium salt-containing, secondary, Fe-rich, and other particles. On average, the black carbon aerosols accounted for 26.8% and 34.2%(relative number abundance) in the 2011 and 2018 samples, respectively. We classified the black carbon particles into four types in terms of elongation, aspect ratio, and whether they were combined with other matter: floc or spreading structure, branched chain, agglomeration, and impaction(aggregation inlaid with or adhered to other substances), which reflect the different aging processes. In the 2011 samples, the branched chain-and agglomerationblack carbon aerosols outnumber the spreading structure-and impaction-ones, which is contrary to the 2018 samples. This observation suggests that the aging extent of black carbon particles in the 2011 samples is higher than that in the 2018 samples, consistent with the progress of haze events. The results highlight that there might be a great change in wintertime haze pollution characteristics and fuel usage in Taiyuan City in 2018 compared to 2011.更多还原