Investigation of PAHs, nitrated PAHs and oxygenated PAHs in PM10 urban aerosols. A comprehensive data analysis

Polycyclic aromatic compounds (PACs) in particulate matter contribute considerably to the health risk of air pollution. As such, we have optimized a method to determine the levels of polycyclic aromatic hydrocarbons, especially nitrated and oxygenated polycyclic aromatic hydrocarbons, in samples of PM₁₀ particulate matter using microwave-assisted extraction (MAE) and gas chromatography coupled to a triple quadrupole mass spectrometer (GC-MS/MS). The proposed method was applied to the analysis of real samples collected in the urban area of Ciudad Real (Spain) during one year. The median total concentrations of eighteen PAHs (∑PAHs) and seven OPAHs (∑OPAHs) were 0.54 and 0.23 ng m⁻³, respectively, with the corresponding value for NPAH (∑NPAHs) being 0.03 ng m⁻³ (only detected in 40% of samples). A clear seasonal trend was observed, with higher levels in the cold season and lower in the warm season for ∑PAHs. The same effect was observed for ∑OPAHs, which exhibited a median concentration of 0.72 ng m⁻³ in the cold season and 0.10 ng m⁻³ in the warm season, and for ∑NPAH, which exhibited a median of 0.04 ng m⁻³ in the cold season but were not detected in the warm season. Molecular diagnostic ratios and PCA (principal component analysis) showed a predominantly traffic origin for PACs. The sources of PAHs also depend on meteorological conditions and/or atmospheric reactions, as confirmed by means of statistical analysis. The ∑OPAH/∑PAH and ∑NPAH/∑PAH ratios were higher in the cold season than the warm season, thus suggesting that PAH derivatives originated from primary combustion emission sources together with their parent PAHs. The concentration range found for benzo(a)pyrene was 0.006–0.542 ng m⁻³, which is below the threshold value of 1 ng m⁻³ established in European legislation as the annual average value. The lifetime lung risk from inhalation of PM₁₀-bound PACs was estimated to be six cancer cases per million people using the World Health Organization method.