Insight into the diurnal variations and potential sources of ambient PM2.5-bound polycyclic aromatic hydrocarbons during spring in Northern Taiwan

In recent decades, polycyclic aromatic hydrocarbons (PAHs), the primary organic pollutants associated with particulate matter (PM), have attracted significant attention due to their carcinogenic and mutagenic potential. However, past studies have lacked exploration into the diurnal variation characteristics of PAHs, primarily due to limited analytical technical capabilities. This study utilized a thermal-desorption device coupled with gas chromatography/mass spectrometry (TD-GC/MS) to identify the levels of PAHs in PM2.5 during short periods (3-hr) and aimed to investigate the diurnal variations, possible sources, and potential health risks associated with PM2.5-bound PAHs in northern Taiwan. The mean concentration of total PAHs in PM2.5 was 1.22 ± 0.69 ng m−3 during the sampling period, with high molecular weight PAHs dominating. Source apportionment by the positive matrix factorization (PMF) model indicated that industrial emissions and traffic emissions (57.7 %) were the predominant sources of PAHs, with petroleum volatilization and coal/biomass combustion (42.3 %) making a lesser contribution. Diurnal variations of industrial and traffic emissions showed higher concentrations during traffic rush hours, while petroleum volatilization and coal/biomass combustion displayed higher concentrations at noon. Results from the potential source contribution function (PSCF) and the concentration weighted trajectory (CWT) model suggested that industrial emissions and traffic emissions mostly originated from local sources and were concentrated in the vicinity of the sampling site and the coastal area of western Taiwan. Source-attributed excess cancer risk (ECR) showed that industrial and traffic emissions had the highest cancer risks during morning traffic peak hours (1.69 ×10−5), while petroleum volatilization and coal/biomass combustion reached the maximum at noon (4.75 ×10−6). As a result, efforts to reduce PAH emissions from industrial and vehicle exhaust sources, especially during morning traffic hours, can help mitigate their adverse impact on human health.