南京雾、霾期间含碳颗粒物理化特征变化分析

Insights into characteristics of carbonaceous particles during haze and fog events in Nanjing

利用单颗粒飞行时间质谱仪(SPAMS)对南京2014年8~9月内清洁、霾及雾时段内含碳颗粒物的理化特征进行分析,归类得到EC-fresh、EC-SN、NaK-EC、OC、ECOC、ECOC-S、ECOC-SN和Ammonium等8大类含碳颗粒物.雾和霾时段内,OC占比出现明显降低,而EC-SN和NaK-EC的占比约为清洁时段内的2倍.清洁时段内含碳颗粒物总占比的减小率>雾>霾.雾时段内各含碳颗粒物中硝酸组分出现富集,有更多小粒径段的OC生成.EC-SN和NaK-EC的颗粒物酸度(R_(va))表现为清洁时段<霾<雾,OC和ECOC-SN的Rva值则在清洁时段达到最大.此次分析得到的含碳气溶胶理化特征有助于对南京不同天气条件下大气碳气溶胶的来源及其在大气中的传输与演变过程的理解.

This study discussed the physicochemical properties of carbonaceous particles in Nanjing from August toSeptember,2014,using a real-time single particle aerosol mass spectrometry(SPAMS).Single carbonaceous particle massspectra were grouped into8types,including EC-fresh,EC-SN,NaK-EC,OC,ECOC,ECOC-S,ECOC-SN andAmmonium.The number fraction of OC in total particles decreased in fog and haze periods while EC-SN and NaK-ECshowed the opposite trend,about2times larger than clean episodes.The reduced rate of the total number fraction ofcarbonaceous particles in clean episodes>fog>haze.Most particles mixed with more nitrate in fog,meantime,more OCwith small diameter were produced in these episodes.The relative acidity ratios(Rva)of EC-SN and NaK-EC in cleanepisodes<haze<fog,while for OC and ECOC-SN,the Rva reached the maximum during clean episodes.This study isimportant for further understanding of the sources and evolution of carbonaceous particles under different weatherconditions in Nanjing.