北京市PM_(2.5)中主要重金属元素污染特征及季节变化分析

Concentration Characteristics and Seasonal Trend of Main Heavy Metal Elements of PM_(2.5) in Beijing

利用2005年4月18日—2008年9月27日北京市中国地质大学(东门)采样点的PM2.5质量浓度变化与重金属Cd、Pb、As、Cu及Zn等污染特征,结合最新发布的《环境空气质量标准》(GB3095—2012),初步分析了近4年时间里北京市单点PM2.5的污染水平及主要重金属污染元素的变化特征,得出了一些有意义的认识。2005年春季—2008年春季期间PM2.5质量浓度为13.1～171μg/m3之间变化,平均浓度为65.6μg/m3,超过最新环境空气质量标准制定的PM2.5年平均浓度限值35μg/m3,北京市PM2.5污染形势依然严峻。奥运会及残奥会期间PM2.5的24 h质量浓度平均值为40.7μg/m3,没有超标。北京市PM2.5中的重金属元素含量及富集特征随着不同年份不同季节差别较大,典型的城市污染元素As在冬季质量浓度最高。对比环境空气质量标准的参考浓度限值发现,As元素的质量浓度在研究期间的年均值均超过了年平均浓度参考限值0.006μg/m3。化学分析结果显示人为污染是PM2.5中Cu、Cd、Pb、Zn、As重金属污染的主要来源,其中As污染需要引起足够重视。研究结果对于北京市大气污染防治具有一定的借鉴意义。

Based on the data of the systematic sampling and analysis of PM2.5 from April 18,2005 to September 27,2008 at the east gate of China University of Geosciences,and the newest ambient air quality standard（GB3095-2012）,some valuable results were derived from primary analysis on mass concentration characteristics and seasonal variations of PM2.5 and main heavy metal elements Cd,Pb,As,Cu and Zn in it.The results showed that the mass concentration of PM2.5 ranged between 13.1 and 171 μg/m3 with the median of 65.6 μg/m3 for the whole sampling period from spring 2005 to spring 2008,that exceeded the limiting value 35 μg/m3 of the national standard II（GB3095-2012）.This indicated that the pollution of PM2.5 was critical.The average 24 hour concentrations of PM2.5 during the Olympic Games and Paralympic Games was 40.7 μg/m3,not exceeding the national standard II.Mass concentration of heavy metal elements in PM2.5 differed between different seasons in different years.The enrichment characteristics for mass concentration of arsenic was the highest among the typical urban pollution elements in winter time.Chemical analysis indicated that diffuse pollution from many different anthropogenic emissions were the main sources of heavy metal pollution such as Cu,Cd,Pb,Zn and As in PM2.5,especially for As,which need to pay more attention on it.This study is only a small contribution to the prevention and control of atmospheric pollution in Beijing.