Six-year trends of concentration, chemical composition, sources and health risks of halogenated, nitro and oxygenated PAHs in winter PM2.5 at a rural area in northern China (2019–2024)

Polycyclic aromatic hydrocarbon (PAH) derivatives have attracted increasing attention due to their stronger persistence and toxicity compared to parent PAHs. Atmospheric PM_2.5 concentration in rural areas of northern China significantly exceeds urban levels, primarily due to widespread coal combustion and inefficient emission control measures. We conducted a six-year winter PM_2.5 sample collection (2019–2024) in rural coastal areas of North China, and analyzed 40 PAH derivatives (14 BrPAHs, 7 ClPAHs, 14 NPAHs, and 5 OPAHs) concentrations. ∑BrPAHs, ∑ClPAHs, ∑OPAHs exhibited significantly lower concentrations during 2020–2021 and followed by an increase in 2022. The results indicated that COVID-19 control measures were effective in reducing pollution levels of these pollutants. The dominant species of BrPAHs, ClPAHs, NPAHs, and OPAHs were 7-BrDahA (21.52 %–26.86 %), 9-ClANT (25.25 %–27.59 %), 2+3N-FLT (30.72 %–39.24 %) and 9,10-ATQ (62.42 %–82.96 %), respectively. The lockdown measures effectively reduced contributions from coal/biomass combustion, traffic, and industrial sources. Coal/biomass combustion and traffic emissions rebounded rapidly after epidemic lockdown, while industrial emissions exhibited delayed recovery. The incremental lifetime cancer risks of PAH derivatives reached lowest level in 2021, then gradually increased after restrictions were lifted, and all were less than 10⁻⁶. Coal/waste combustion was the dominant health risk source for Cl/BrPAHs, while traffic emissions and secondary formation contributed most to NPAHs-associated risks.