Risk evaluation of particle-bound polycyclic aromatic hydrocarbons (pPAHs) at roadside air environment in Bangkok by time-series analysis and its application to urban traffic management

经泰国污染控制部门(PCD)许可，在今年4月(旱季)，在三个路边监测站和两个一般监测站使用PAS(光电子气溶胶传感器)连续监测PPAHS(颗粒结合多环芳烃)一个月。与去年9月(雨季)的结果相比，浓度水平出人意料地低。这不是由于交通量的变化，而主要是由于风向的季节模式的差异。此外，用粒度收集器分别采集了颗粒物，并用GC/MS分析了12种分别给出致癌风险的多环芳烃，如苯并(A)芘，从聚类分析的结果可以看出，在粒度为1μm时，颗粒状多环芳烃的组成发生了明显的变化。1μm以上颗粒物的多环芳烃组成在旱季和雨季有所不同。这可能是由于雨季周期性阵雨减少了颗粒物在空气环境中的停留时间，从而增加了低分子尺寸的多环芳烃。此外，泰国在PCD实验室测量了不同类型车辆(16辆重型车辆和12辆轻型车辆)在标准驾驶模式下的多环芳烃单位排放量。这是与朱拉隆科恩大学的Tassanee博士合作完成的。利用我们的现场调查结果和现有的数据，从降低PAHs暴露风险的角度对不同的模式转换、车辆类型调整等情况进行了评估，为交通管理提供了思路。这些结果在最终报告中进行了总结。

Continuous monitoring of pPAHs (particle-bound polycyche aromatic hydrocarbons) by using PAS (photoelectron aerosol sensor) at three roadside monitoring stations and two general stations with a permission by Pollution Control Department (PCD), Thailand for one month in April (dry seasons) this year. Comparing the results obtained in last September (rainy season), the concentration level was unexpectedly low. This was not due to the traffic amount change but mainly due to the difference in seasonal pattern of wind direction. Furthermore, particles were separately collected by a size-wise particle collector and twelve PAHs to which the unit cancer risk is respectively given, such as benzo(a)pyrene, were analyzed by a GC/MS. The particle-wise PAH composition was clearly changed at the particle size of 1μm, judging from the result of cluster analysis. The composition of PAHs of particles at above 1μm was different between the dry season and the rainy season. This is probably due to an increase in lower molecule-size PAHs by a decrease in particle residence time in air environment by a periodical shower in the rainy season. In addition, the unit emission of PAHs from different type of vehicles (16 heavy duty vehicles and 12 light duty vehicles) at a standard driving mode in Thailand, was measured at a PCD laboratory. This was done in collaboration with Dr.Tassanee, Chulalonkorn University. By using our field survey results and presently available data, different scenarios of modal shift, regulation of vehicle type, and so on, was evaluated in the light of risk reduction of PAHs exposure, giving an idea of the way for traffic management. These results was summarized in the final report.