北京4个功能区春冬季大气重污染期间PM_(10)和PM_(2.5)化学污染特征及影响因素分析

Chemical pollution characteristics of PM_(10)and PM_(2.5) during heavy air pollution in spring and winter in four functional areas of Beijing and their associated influencing factors

选取北京4个功能区,包括西三环(交通带)、花园北路(商业区)、昌平农村(乡村)、麋鹿苑(郊区)作为研究对象,在2015年春冬季的4次重污染过程分别采集PM_(10)和PM_(2.5)样品,采用主成分分析解析采样期间PM_(10)和PM_(2.5)的污染来源,分析10种水溶性离子、有机碳/元素碳(OC/EC)、16种多环芳烃(PAHs)以及7种重金属元素(Zn、Mn、Pb、Ni、Cu、Cr和As)的污染特征,结合气象条件和后向轨迹,探讨几次典型污染事件形成的气象影响因素及颗粒物化学成分差异。结果表明:采样期间,4月9日、15日的西三环,3月16—17日的花园北路,11月12—16日的昌平农村和3月28—29日的麋鹿苑日均PM_(10)和PM_(2.5)浓度分别大于200和100μg/m 3,超过GB 3095—2012《环境空气质量标准》二类功能区浓度限值,属于重污染天气。4个采样点颗粒物中主要污染物均为二次水溶性离子NO 3-、SO 42-及NH 4+和二次有机碳(SOC)。颗粒物中PAHs以4~6环为主,重金属元素以Zn和Mn为主。4个功能区采样点50%~95%水溶性离子、43%~93%的PAHs、44%~97%的7种重金属元素富集在PM_(2.5)中。不同功能区采样点颗粒物化学组分各有特点,西三环的NO 3-、花园北路的Cl-和NH 4+、昌平农村的NH 4+以及麋鹿苑的Ca2+浓度在总水溶性离子中占比较高;花园北路的PAHs、昌平农村的PAHs和Ni在颗粒物中占比较高。采样期间PM_(10)和PM_(2.5)污染主要来源于燃煤源、交通和二次源以及生物质源。

PM_(10)and PM_(2.5)samples were sampled at four sites located in four functional regions of Beijing,including West 3-Ring Road(traffic site),Huayuan North Road(commercial area),Changping countryside(rural area),and Milu Park(suburban area),during four heavy pollution processes in spring and winter,2015.Principal components analysis(PCA)was used to analyze the sources of PM_(10)and PM_(2.5)obtained from the four sampling sites.The pollution characteristic of chemical components,including ten water-soluble ions,organic carbon/element carbon,16 polycyclic aromatic hydrocarbons(PAHs)and seven heavy metal elements(Zn,Mn,Pb,Ni,Cu,Cr and As),were analyzed.Combined with meteorological conditions and back trajectory,the meteorological influencing factors and the differences of particulate matter chemical compositions of several typical pollution events were discussed.The results showed that the daily-average PM_(10)and PM_(2.5)concentrations of West 3-Ring Road on April 9 and 15,Huayuan North Road on March 16-17,Changping rural area on November 12-16,and Milu Park on March 28-29 were greater than 200 and 100μg/m 3,respectively,which exceeded the ClassⅡconcentration limits in Ambient Air Quality Standards(GB 3095-2012),and belonged to heavy pollution weathers.The major chemical components in the particulate matter at the four sampling sites were secondary water-soluble ions NO 3-,SO 42-,NH 4+and secondary organic carbon(SOC).PAHs in the particles were mainly 4-6 rings,and the heavy metals were mainly Zn and Mn.About 50%-95%of water-soluble ions,43%-93%of PAHs and 44%-97%of seven heavy metals in the four functional areas were concentrated in PM_(2.5).The chemical components of particulate matter in different functional areas featured in their own chemical characteristics.Higher fractions of water-soluble ions were observed for NO 3-at West 3-Ring Road,Cl-and NH 4+at Huayuan North Road,NH 4+at Changping countryside and Ca2+at Milu Park.In addition,greater fractions of particulate matters were found for PAHs in Huayuan North Road,and Ni and PAHs in Changping rural site.During the sampling period,the major sources contributing to PM_(10)and PM_(2.5)were coal combustion,mobile and secondary sources,as well as biomass sources.