天津市公交站微环境中PM10的碳组分特征分析及来源解析

On the pollution source apportionment and the characterization of carbon fractions in PM_(10) at the bus stops in Tianjin

于2012年9月对天津市两公交站,分2个时段采集可吸入颗粒物(PM10)样品,并用热光反射分析仪测定其中的碳组分含量,以期了解公交站微环境PM10中碳组分的分布及来源。结果表明,采样期间,公交站日均PM10质量浓度为(323±155)μg/m3,其中OC日均质量浓度为(42.5±12.5)μg/m3,EC日均质量浓度为(12.8±7.00)μg/m3。与其他微环境(远离交通)的平均PM10、OC、EC质量浓度相比,公交站微环境中的颗粒物及其碳组分质量浓度最高,表明污染严重。PM10中OC和EC相关系数为0.805,相关性显著,显示PM10中OC、EC来源相同。运用主成分分析法(定性)和化学质量平衡模型(定量)对样品中碳组分进行两阶段递进式来源解析,识别出秋季公交站微环境PM10中碳组分主要来源于道路扬尘,其次为烹饪烟气和机动车尾气。

The paper is aimed at introducing our research findings on the carbon pollution source apportionment in PM10 in the microenvi- ronments of the bus stops in Tianjin. To accomplish our research, we have managed to collect PM^0 samples simultaneously at the two bus stops （i. e. Haiguangxi and Balitai ） separately in Tianjin, in September, 2012. We have collected the samples during the period of five hours each day in the rush hours. The bus stops mentioned above are located in a mixed zone of residential quarters and the busy-traffic spots. In our sample-collecting process, we have adopted a thermal/ optical reflectance （TOR） method to detect the concentrations of ele- mental carbon （EC） and organic carbon （OC） in the said samples, along with the lnteragency Monitoring of Protected Visual Environ- ments （IMPROVE） protocol. The results of our study have shown that the average mass concentration rates of PM10, OC and EC at the bus stops were equal to （323 ＋ 155） μg/m3, （42.5 ＋ 12.5） μg/m3and （12.8 ＋ 7.00） μg/m3, respectively. The daily average concentration rate of PM10 exceeds class 2 of the Ambient Air Quality Standard, whereas the concentrations of PM10, EC and OC at the bus stops were found about 90%, 20% and 50% higher than those at other mi- eroenvironments in the space away from the traffic points, respective- ly. Therefore, it is necessary to study the concentrations of PM10 and carbon emission in the microenvironment of the bus stops. Moreover, we have also noticed a good correlation （ r = 0. 805） between OC and EC, indicating that they have had their own same common main sources of gas and petro combustion. Emission sources apportionment of the total carbon in PMl0 has been given by using principal compo- nent analysis （qualitative） and the chemical mass equilibrium model （quantitative） with eight kinds of thernlos-derived carbon fractions. The results of PCA analysis thus reveal that the vehicle exhaust emis- sion, coal burning, cooking and biomass burning are the main sources of such air pollution. And, similarly, the results of CMB model prove that 52 % of TC pollution should be attributed to the road dust, whereas 25% of them--to food cooking, and 14%-to the ve- hicle exhaust, plus the rest 9 % to coal burning. Both the two meth- ods demonstrate that the road dust, cooking and vehicle exhaust emis- sion are of the primary sources of particulate pollution so far as we have discovered in the microenvironment of the bus stops in the au- tumn season in Tianjin.