天津市春季样方法道路扬尘碳组分特征及来源分析

Characteristics and Source Apportionment of Carbon Components in Road Dust PM_(2.5) and PM_(10) During Spring in Tianjin Derived by Using the Quadrat Sampling Method

为研究天津市春季道路扬尘PM_(2.5)和PM_(10)中碳组分特征及来源,于2015年4月用样方法采集天津市道路扬尘样品,利用再悬浮采样器将样品悬浮到滤膜上,经热光碳分析仪测定有机碳(OC)和元素碳(EC),利用非参数检验、OC/EC比值分析、相关分析及聚类分析对其污染特征和来源进行探讨.结果表明,PM_(2.5)中ω(TC)为4. 89%(次干道)～18. 83%(快速路),ω(OC)为3. 57%(次干道)～15. 39%(快速路),ω(EC)为1. 32%(次干道)～3. 44%(快速路); PM_(10)中ω(TC)为8. 14%(次干道)～19. 71%(快速路),ω(OC)为5. 91%(次干道)～16. 28%(快速路),ω(EC)为1. 96%(主干道)～3. 43%(快速路);快速路中各碳组分质量分数均较高,次干道中各碳组分质量分数均较低,可能是由于快速路中车流量较大,机动车尾气排放量较大,而次干道车流量较小;各类型道路中ω(OC)明显大于ω(EC),ω(EC)在不同道路类型中差异不大;两相关样本非参数检验表明,各碳组分质量分数在PM_(2.5)和PM_(10)间均无显著性差异;相关性分析表明道路扬尘中OC、EC来源大致相同.通过OC/EC比值分析及聚类分析可知,天津市春季道路扬尘中碳组分主要来源于燃煤、机动车尾气以及生物质燃烧.

In order to study the characteristics and sources of carbon fractions in PM2.5 and PM10 of road dust in Tianjin,samples of road dust were collected by the quadrat sampling method in April 2015 in Tianjin,and samples were re-suspended on filters by using a NK-ZXF sampler. A Thermal Optical Carbon Analyzer(IMPROVE-TOR) was employed to measure the concentrations of organic carbon(OC) and elemental carbon(EC),and the pollution characteristics and sources were investigated by non-parametric tests and OC/EC ratio,correlation,and cluster analyses. The results showed that ω(total carbon,TC) in PM2.5 of road dust amounted to 4. 89%(secondary road)-18. 83%(expressway),ω(OC) amounted to 3. 57%(secondary road)-15. 39%(expressway),and ω(EC) amounted to 1. 32%(secondary road)-3. 44%(expressway);meanwhile,ω(TC) in PM10 of road dust was 8. 14%(secondary road)-19. 71%(expressway),ω(OC) was 5. 91%(secondary road)-16. 28%(expressway),and ω(EC) was 1. 96%(main road)-3. 43%(expressway). The mass fraction of each carbon component for the expressway was relatively high,and that for the secondary trunk road was relatively low,which may have been due to the large traffic volume on the expressway and corresponding large amounts of exhaust emissions from motor vehicles,whereas there were fewer vehicles on the secondary trunk road. Additionally,ω(OC) was significantly larger than ω(EC) for all types of roads,and ω(EC) did not vary much among the different road types. The non-parametric tests of two related samples showed that there was no significant difference in the mass fraction of each carbon component between PM2.5 and PM10. The correlation analysis showed that the sources of OC and EC in road dust were roughly the same. The OC/EC ratio analysis and cluster analysis showed that the main sources of the carbon components in the dust of roads in Tianjin in spring were coal combustion,motor vehicle exhaust,and biomass burning.