Size-segregated nitrated aromatic compounds in PM₁₀ and potential health risks in Guangzhou, South China

Nitrated aromatic compounds (NACs) are toxic, light-absorbing components of particulate matter, impacting both human health and climate. This study conducted a 14-day field campaign at an urban site in Guangzhou, southern China, collecting size-segregated aerosol samples at cutting points of 0.49, 0.95, 1.5, 3.0, 7.2, and 10 μm, to analyze NAC size distribution, light absorption, and toxicity. Nearly 90% of NACs were concentrated in particulate matters with aerodynamic diameter smaller than 1.5 μm (PM_1.5). Their concentrations on polluted days strongly correlated with molecular markers from primary emissions, especially from coal combustion. Backward trajectory analysis indicated that northern coal-fired sources significantly contributed to pollution levels. Filter-based light absorption measurements showed that over 90% of brown carbon (BrC) were concentrated in PM_0.95. Despite lower mass concentrations of the 9 toxic NACs compared to the 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs), their Benzo[a]pyrene toxic equivalency quotients (TEQ_BaP) were substantially higher, with 1,6-dinitropyrene, 1,8-dinitropyrene, and 6-nitroperylene accounting for 95% of the TEQ_BaP. 1,6-dinitropyrene was the dominant contributor to NACs’ TEQ_BaP on both clean and polluted days. The TEQ_BaP of NACs exceeded 1.0 ng m⁻³, indicating substantial health risks associated with exposure. These findings highlight the urgent need for emission control to mitigate the health impact of NACs.