2013年1月京津唐地区霾事件气溶胶单颗粒形貌及硫酸盐化特征

2013年1月华北地区经历了重霾过程,为研究其污染特征,使用透射电子显微镜(TEM)及能谱(EDX)对北京、唐山和天津晴天和霾天气下气溶胶单颗粒基本形貌和硫酸盐化特征进行了分析。结果表明,华北地区气溶胶单颗粒包括矿物颗粒、硫酸盐颗粒、金属氧化物、烟尘集合体、有机颗粒和飞灰,仅在天津市样品中发现少量的Na Cl颗粒。对单颗粒的元素组成进行统计表明,华北地区晴天以富Si颗粒为主(31.0%),其次为富Ca颗粒(18.3%)、富Fe颗粒(14.1%)、富Cl颗粒(12.2%)等,霾天以富S颗粒为主(47.4%),其次为富Si颗粒(21.1%)和富Fe颗粒(13.4%)等。霾天气富Ca颗粒明显减少,同时在含S较高的颗粒中也含有Ca、K等元素,说明大气中含Ca、K等碱性矿物对雾水酸性有一定的缓冲作用。不同天气含S颗粒差异较大,霾天气明显高于晴天,S/Ca平均值在霾天明显较高,且大于0.8,说明在一定的SO2浓度下,大气湿度越大,硫酸盐化现象越明显,生成大量的硫酸铵盐。

Morphologies and sulfation characteristics of individual aerosol particles in the haze episode over the Beijing-Tianjin-Tangshan area in January 2013

A series of hazes occurred over the North China plain in January 2013. In this paper, the authors analyzed the morphologies, elemental compositions and sulfation characteristics of the individual aerosol particles collected in Beijing, Tianjin and Tangshan cities in January 2013 by Transmission Electron Microscopy(TEM) coupled with Energy Dispersed X-ray Spectrometry(EDX). The results showed that the individual aerosol particles could be subdivided into mineral particles, sulfate particles, metal oxide particles, soot aggregates, organic particles, and fly ash. A small amount of sea salt particles was found only in the Tianjin samples. According to element compositions, the individual particles were dominated by Si(31.0%), Ca(18.3%), Fe(14.1%) and Cl(12.2%) in the sunny days, and by S(47.4%), Si(21.1%) and Fe(13.4%) in the haze days. The high-S particles were commonly associated with higher values of Ca and K, indicating that alkaline minerals could be buffered against the acid mist. An analysis of sulfation characteristics showed that the S-bearing particles were more common in haze days, and that the S/Ca ratio was higher(>0.8) in the hazy days, indicating that the haze day is favorable for secondary reactions and formation of the S-rich particles.