北京市道路空气中挥发性有机物时空分布规律

为研究城市交通道路空气中挥发性有机化合物(VOCs)的污染状况、变化规律和不同道路类型的浓度特点，于2008年5月—2009年7月对北京市3种典型道路(街道峡谷、交叉道路和开阔道路)进行空气质量监测. 采用气相色谱法测定道路空气中非甲烷烃(NMHCs)、苯系物(苯、甲苯和二甲苯)的质量浓度. 结果表明:北京市道路空气中挥发性有机化合物污染比较严重，其中ρ(NMHCs)日均值为1.0～3.3 mg/m3，ρ(苯系物)日均值为8.8～80.0 μg/m3. 污染物浓度日变化多呈现双峰型. 选取1，4，7和10月为不同季节的代表月份，7月的ρ(NMHCs)和ρ(苯系物)均最高，10月最低. 3种典型道路中，街道峡谷的污染物质量浓度高于另外2种道路. 道路附近的挥发性有机物质量浓度主要受到机动车排放、气象条件和地形条件等的影响. 

Temporal and Spatial Distribution Rule of Volatile Organic Compounds in Ambient Air around Urban Traffic Roads in Beijing

In order to study the contamination status, exposure characteristics and variation regularity of volatile organic compounds (VOCs) in urban traffic road air, air quality monitoring on three kinds of roads including street canyon, cross road and open road was carried out in Beijing from May 2008 to July 2009. Mass concentrations of non-methane hydrocarbons (NMHCs), benzene, toluene and xylene (BTEX) were analyzed by gas chromatography (GC). Results showed that the pollution caused by VOCs was serious in road air in Beijing. Diurnal average exposure mass concentrations of NMHCs and BTEX were 1.0-3.3 mg/m3 and 8.8-80.0 μg/m3, respectively. Diurnal variations of VOCs mass concentration exhibited two peaks. The mass concentration of VOCs in road air was highest in summer and lowest in autumn, which was influenced significantly by variations of weather conditions in different seasons. Among the three kinds of roads, exposure mass concentration of VOCs in the street canyon was highest. Vehicle emissions, weather conditions and topographic conditions extremely affected exposure mass concentration of VOCs in road air.