使用STAPLEX大流量六级采样器(<0.49μm、0.49～0.95μm、0.95～1.5μm、1.5～3.0μm、3.0～7.2μm和>7.2μm),结合DRI Model 2001热光碳分析仪(TOR),分析了2010年5月～2011年5月期间上海市嘉定区(市郊)、徐汇区(市区)的大气颗粒物样品中有机碳(OC)和元素碳(EC)的粒径分布.结果表明,不同粒径的OC和EC质量浓度均呈双峰分布,较高峰出现于<0.49μm粒径段,次高峰则出现于>3.0μm的两个粒径段.嘉定区(JD)和徐汇区(XH)PM3.0中OC的质量浓度分别为16.35μg.m-3和11.85μg.m-3,EC质量浓度分别为2.22μg.m-3和1.91μg.m-3,市郊大气颗粒物中碳组分质量浓度高于市区,说明市郊碳污染更为严重.在<1.5μm的粒径段,嘉定区OC与EC的同源性较好,表明其中大部分OC来自于燃烧源.两地区不同粒径OC/EC值与不同排放源特征值的对比,可以说明徐汇区更多受到机动车尾气排放和道路扬尘的影响.通过EC示踪法计算二次有机碳(SOC)质量浓度可知:上海市SOC质量浓度较高,PM3.0中达到6.76μg.m-3,占OC的质量分数为69%,粒径分布呈双峰分布,峰值位于0.49～0.95μm和3.0～7.2μm粒径段.
A study was conducted on the effect of atmospheric parameters, including temperature, wind speed, and relative humidity, on fine particulate mass concentrations measured in Jiading District of Shanghai, China, during the period from January 2009 to January 2010. A sensitivity analysis was applied to investigate the interaction between atmospheric parameters and particulate mass concentration. The experiment revealed that the concentration of particulates increased with particle size from 0.1 to 1.0 μm, and decreased with the increase of particle size from 1.0 to 2.5 μm. The effects of atmospheric parameters on fine mass concentrations were significantly particle size-dependent. The PM1.0-2.5 may come from the size increase of smaller particulates after moisture absorption, And the variation of concentrations of PM0.1-l.0 was mainly attributed to the accumulation of PM0.1. The ventilation index and dilution index were calcu- lated on the basis of data collected in December 2009. A correlation analysis indicated that there was a significant relation between these two indexes and the particulate concentration by examining the three particle size ranges, 0.0-0.1, 0.1-1.0, and 1,0-2.5 μm. The Spearman correlation coefficients that related the ventilation index to the concentration for the three particle size ranges were -0.45, -0.56 and -0.47, respectively, while the coefficients that related the dilution index to the concentration were -0.36, -0.42 and -0.45, respectively.
Jian YaoWei LiuWangkun ChenGuanghua WangYoushi ZengYu HuangJun Lin
Sulfate, nitrate and ammonium （SNA） are the dominant species in secondary inorganic aerosol, and are considered an important factor in regional haze formation. Size-fractionated aerosol particles for a whole year were collected to study the size distribution of SNA as well as their chemical species in Shanghai. SNA mainly accumulated in fine particles and the highest average ratio of SNA to particulate matter （PM） was observed to be 47% in the fine size fraction （0.49-0.95 ~tm）. Higher sulfur oxidation ratio and nitrogen oxidation ratio values were observed in PM of fine size less than 0.95 ~tm. Ion balance calculations indicated that more secondary sulfate and nitrate would be generated in PM of fine size （0.49-0.95 p.m）. Sulfur K-edge X-ray absorption near-edge structure （XANES） spectra of typical samples were analyzed. Results revealed that sulfur mainly existed as sulfate with a proportion （atomic basis） more than 73% in all size of PM and even higher at 90% in fine particles. Sulfate mainly existed as （NH4）2SO4 and gypsum in PM of Shanghai. Compared to non-haze days, a dramatic increase of （NH4）2SO4 content was found in fine particles on haze days only, which suggested the promoting impact of （NH4）2SO4 on haze formation. According to the result of air mass backward trajectory analysis, more （NH4）2SO4 would be generated during the periods of air mass stagnation. Based on XANES, analysis of sulfate species in size-fractionated aerosol particles can be an effective way to evaluate the impact of sulfate aerosols on regional haze formation.
