Application of thermal desorption for measuring PAHs on PM_2.5

PM_2.5 and polycyclic aromatic hydrocarbons (PAHs) emitted from various sources may cause respiratory disease and lung cancer. Additionally, PAHs deposited on PM_2.5 would aggravate the hazard to human health once inhaled. Therefore, it is essential to investigate the PAHs adsorbed on PM_2.5 in ambient air. However, analysis of PAHs on PM_2.5 is limited so far due to high detection limit of the analytical method and complex pretreatment procedures of the sample. In this study, thermal desorption (TD) is combined with GC-HRMS for direct analysis of PAHs on PM_2.5 collected by the filter without pretreatment. The results indicate that distribution of PAHs on the filter is uniform and each filter section is representative for direct analysis of PAHs on PM_2.5. The optimal thermal desorption temperature and purge time of analysis are found at 320°C and 60 s, respectively. Furthermore, the PAHs on PM_2.5 of ambient air in Taiwan including traffic area, industrial area, suburban area, and background site are investigated. The results indicate that the concentrations of PAHs on PM_2.5 in ambient air of Northern, Central, and Eastern Taiwan are in the range of 0.13-6.63 ng/m³, with an average concentration of 2.23 ng/m³. The PAH concentration measured in winter is significantly higher than that in summer, and the concentration of PAHs on PM_2.5 ranges from 0.071 to 0.280 ng/μg while the average concentration is 0.133 ng/μg. The technology optimized in this study can be applied for rapid and accurate measurement of PAHs present on fine particles.