北京市采暖期PM2.5中有机碳和元素碳的污染特征与来源解析

为研究北京市采暖期PM2.5中有机碳(organic carbon,OC)和元素碳(elemental carbon,EC)的污染特征和来源,于2011年12月至2012年2月在北京师范大学监测点进行PM2.5样品的采集.本研究分析PM2.5及其OC和EC的质量浓度变化特征,并采用ρ(OC)/ρ(EC)最小比值法估算二次有机碳(secondary organic carbon,SOC)的质量浓度.除此之外,从定性和定量两方面研究OC和EC的来源及其来源贡献量.结果表明:北京市采暖期PM2.5平均质量浓度为(90.69±61.86)μg/m3,其中OC和EC的平均质量浓度分别为(21.91±12.02)、(5.03±2.58)μg/m3,分别占PM2.5的24.16%和5.55%;SOC的平均质量浓度为(8.37±6.05)μg/m3,占总有机碳(total organic carbon,TOC)质量浓度的37.27%.PM2.5中OC和EC的相关系数较高,表明它们来源相同,且主要来源于机动车尾气、燃煤排放.机动车尾气排放的贡献量达44.70%,成为OC、EC的重要来源.因此,严格控制机动车保有量的快速增长,减少机动车尾气排放,将成为改善城市大气环境质量的重要手段之一.

Characteristics and Source Apportionment of Organic Carbon and Elemental Carbon in PM2.5 During the Heating Season in Beijing

This paper investigated the characteristics and sources of organic carbon(OC) and elemental carbon(EC) in PM2. 5during the heating season in Beijing. PM2. 5samples were collected at the Beijing Normal University sample site during the period of December 2011 to February 2012. This study also analyzed the concentrations characteristics of PM2. 5,OC and EC,calculated the concentrations of the secondary organic carbon(SOC) based on the minimum ρ(OC)/ρ(EC) ratio method. Besides,the sources and source contributions of OC and EC were analyzed qualitatively and quantitatively. Results showed that the average concentration of PM2. 5was(90. 69 ± 61. 86) μg/m3,the average concentration of OC and EC were(21. 91 ± 12. 02),(5. 03 ± 2. 58) μg/m3,accounting for 24. 16% and 5. 55% of PM2. 5,respectively. The average concentration of SOC was(8. 37 ± 6. 05) μg/m3,accounting for37. 27% of the total organic carbon(TOC). The high correlation coefficient of OC and EC showed that the source for OC and EC was the same,mainly from the vehicle emission,the coal combustion. The vehicle emission was the major source,with a contribution of 44. 70% to the OC and EC. As a consequence,controlling the number and reducing the emissions of motor vehicles have become an important measure to improve the atmospheric environment quality in urban areas.