Pollution characteristics and risk assessment of ambient PM2.5-bound PAHs and NPAHs in typical Japanese and New Zealand cities and rural sites

Abstract Nine polycyclic aromatic hydrocarbons (PAHs) and six nitro-PAHs (NPAHs) were measured in PM 2.5 samples collected over one year (2016–2017) in two cities: Kanazawa (Japan) and Auckland (New Zealand) and their respective rural background sites: Wajima in Noto Peninsula (Japan) and Tapora in Okahukura Peninsula (New Zealand). The mean concentrations of ΣPAHs and ΣNPAHs followed similar distribution profiles in both countries, with higher concentrations in the urban than rural sites. The mean of ΣPAHs in Kanazawa City was 0.53 ng/m 3 and represented the highest total concentration compared to the other three sites. Conversely, the highest ΣNPAHs concentrations were measured in Auckland City (48.2 pg/m 3 ). Diagnostic ratios and principal component analysis revealed that automobiles were the main sources of PAHs and NPAHs in both cities, whereas coal combustion and domestic wood burning were the dominant sources of PAHs and NPAHs in rural sites in Japan and New Zealand. Back trajectory analyses showed that high levels of PAHs detected at Wajima were the result of long-range transport from China and Mongolia in winter, which was not observed at the other sites. Considering the adverse health effects of PM 2.5 , further studies and continuous monitoring of atmospheric PAHs and NPAHs are necessary to evaluate mitigation strategies in both hemispheres.