太原市PM_(2.5)中碳质组分季节变化与组成特征

Characterization and Seasonal Variation of Carbonaceous Aerosol in Urban Atmosphere of Taiyuan

2013年10月至2014年7月,在太原市区,分4个月采集大气细颗粒物,共采集120个PM_（2.5）样品,分析了颗粒物及其有机碳（OC）和元素碳（EC）浓度。结果表明,采样期间大气中PM_（2.5）的日均浓度为（300±132）μg/m3,PM_（2.5）超国家二级标准较严重,大致呈现春季〉冬季〉秋季〉夏季的季节变化特征。大气PM_（2.5）样品中OC和EC的含量变化范围分别为3.6~137和0.8~19.3 g/m3,季节变化与颗粒物浓度不一致,呈现为冬季〉秋季〉春季〉夏季的季节变化特征。利用核磁共振仪分析了典型样品中碳质组分的结构组成。结果显示,烷基碳、烷基取代芳香烃碳和氧取代的芳烃或者酚醛树脂类碳是气溶胶中有机质的主要组成成分;秋冬季样品中,羧基碳和氧取代碳相对含量较高,主要来源于生物质燃烧;春季羟基类化合物增加显著,主要来源于地表土壤中的糖类;夏季样品中,来源于生物排放的烃类化合物和机动车排放的芳香烃相对含量较高。

Total 120 PM_（2.5）samples were collected at urban Tiayuan from October 2013 to July 2014. Results indicated that averaged PM_（2.5）concentrations were 300±132 μg/m3, which was much higher than the Grade Ⅱ of National Standard（70 μg/m3, daily）. Organic carbon（OC） and element carbon（EC） were in the range of 3.6 ~137 μg/m3 and 0.8 ~19.3 μg/m3,respectively. Seasonal variation data were characterized by higher concentration in winter than in summer. In addition, 4aerosol filter samples collected in different seasons were analyzed using solid-state nuclear magnetic resonance（13C-NMR）spectroscopy to determine relative concentrations of carbon functional groups. The results indicate that organic in Taiyuan atmospheric aerosol particles is mainly composed of alkyl, alkyl-substituted aromatic and oxygen-substituted aromatic or phenolic functional groups. For the samples in fall and winter, the carboxyl and oxygen replaced functional groups are relatively higher, mainly from biomass burning. The relative abundance of hydroxyl functional groups increase significantly in spring, mainly from the source of sugars in surface soil resuspended; the increase of alkyl carbons and aromatic hydrocarbons in summer sample mainly from the source of biogenic and vehicle emissions, respectively.