Size distribution and source of black carbon aerosol in urban Beijing during winter haze episodes
Size distribution and source of black carbon aerosol in urban Beijing during winter haze episodes
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冬季雾霾期间北京城区黑碳气溶胶粒径分布及来源
DOI：
10.5194/acp-17-7965-2017
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发表时间：
2017
影响因子：
6.3
通讯作者：
Zhang Renjian
中科院分区：
文献类型：
--
作者：
Wu Yunfei;Wang Xiaojia;Tao Jun;Huang Rujin;Tian Ping;Cao Junji;Zhang Leiming;Ho Kin-Fai;Han Zhiwei;Zhang Renjian
摘要。黑碳（blackberry carbon， BC）的光吸收能力对气候和环境有着重要的影响，这在很大程度上取决于其物理化学性质，包括形态、大小和混合状态。利用单粒子烟尘光度计（SP2）对2014年雾霾频发的冬末北京城区难熔BC （rBC）的粒径分布进行了研究。假设无空洞rBC的密度为1.8 g cm−3，rBC的质量呈近似对数正态分布，作为体积当量直径（VED）的函数，其峰值直径为213 nm。在污染期间观察到的rBC的VED值比在清洁日时更大，这意味着rBC来源发生了变化，因为来自某一来源的rBC的大小分布相对稳定，而单个rBC的VED一旦排放到大气中变化很小。潜在源贡献函数分析表明，观测点自南向东的气团带来了更高的rBC负荷，且涂层更厚，核心尺寸更大。rBC的平均VED与厚包被rBC的数量分数呈显著的线性相关，推断完全未包被或薄包被的rBC为~ 150 nm。在本研究中，它被认为是来自当地交通来源的rBC的典型平均VED。据估计，当地交通对每小时红细胞质量浓度的贡献为35%至100% %，在活动期间平均为59% %。在污染期间，观察到当地交通对rBC的贡献较低，这表明其他来源（如煤燃烧和生物质燃烧）对rBC的贡献增加。因此，北京的重污染除了受到当地交通的影响外，还受到其他来源的影响。
Abstract. Black carbon (BC) has important impact on climate and environment due to its light absorption ability, which greatly depends on its physicochemical properties including morphology, size and mixing state. The size distribution of the refractory BC (rBC) was investigated in urban Beijing in the late winter of 2014, during which there were frequent haze events, through analysis of measurements obtained using a single-particle soot photometer (SP2). By assuming void-free rBC with a density of 1.8 g cm−3, the mass of the rBC showed an approximately lognormal distribution as a function of the volume-equivalent diameter (VED), with a peak diameter of 213 nm. Larger VED values of the rBC were observed during polluted periods than on clean days, implying an alteration in the rBC sources, as the size distribution of the rBC from a certain source was relative stable, and VED of an individual rBC varied little once it was emitted into the atmosphere. The potential source contribution function analysis showed that air masses from the south to east of the observation site brought higher rBC loadings with more thick coatings and larger core sizes. The mean VED of the rBC presented a significant linear correlation with the number fraction of thickly coated rBC, extrapolating to be ∼ 150 nm for the completely non-coated or thinly coated rBC. It was considered as the typical mean VED of the rBC from local traffic sources in this study. Local traffic was estimated to contribute 35 to 100 % of the hourly rBC mass concentration with a mean of 59 % during the campaign. Lower local traffic contributions were observed during polluted periods, suggesting increasing contributions from other sources (e.g., coal combustion and biomass burning) to the rBC. Thus, the heavy pollution in Beijing was greatly influenced by other sources in addition to the local traffic.