Spatiotemporal distribution of PAHs and levoglucosan in fine and ultrafine PM across Southern Thailand: Insights from a novel GC-MS approach

A sensitive GC-MS method was developed for the simultaneous quantification of polycyclic aromatic hydrocarbons (PAHs) and levoglucosan (L) in ambient particulate matter (PM) without the need for derivatization. This method enhanced the analytical response of L by 73.6% compared to previous techniques. Extraction conditions were optimized, improving recovery and reducing detection limits. The method was applied to PM samples collected from Phuket, Songkhla, and Surat Thani in Southern Thailand between June 2023 and May 2024. Size-segregated PM analysis revealed the highest mass concentrations in the fine fraction (2.5–10 µm), with Surat Thani exhibiting the highest overall levels. L concentrations peaked in the 0.5–1.0 µm fraction, while PAHs were most abundant in the 1.0–2.5 µm range. Elevated levels of PM and PAHs were observed during the northeast monsoon in Phuket and Surat Thani, whereas Songkhla experienced higher concentrations during the southwest monsoon and transboundary haze period (September–October 2023), likely linked to biomass burning in Indonesian. L concentrations in Songkhla were significantly elevated during this period, indicating long-range transport, as supported by backward trajectory analysis. Source apportionment suggested that PAHs were mainly from high-temperature combustion sources. Toxicity assessment showed TEQ values below the EU limit, with the highest in Surat Thani (0.438 ng m⁻³). Incremental cancer risk (ICR) values ranged from 1.25 × 10⁻⁵ to 2.34 × 10⁻⁵ m³ ng⁻¹. Overall, this study presents an efficient method for PAH and L quantification and provides critical insights into the spatiotemporal distribution and health risks associated with PM pollution in Southern Thailand. • A GC-MS method was developed for simultaneous PAH and levoglucosan analysis without derivatization. • Levoglucosan sensitivity improved by 73.6% with lower detection limits. • Levoglucosan in PM₀.₁ was identified for the first time, peaking in the 0.5–1.0 µm fraction. • PAHs were most concentrated in the 1.0–2.5 µm particulate size range. • Biomass burning during the monsoon season elevated PM and PAH levels in Southern Thailand.