Sources and spatial distribution of PM2.5-bound polycyclic aromatic hydrocarbons in Zhengzhou in 2016

Abstract

Atmospheric polycyclic aromatic hydrocarbons (PAHs) in PM2.5 were analyzed in 2016 at five representative sites in Zhengzhou, China to determine their seasonal and spatial characteristics. The annual PM2.5 concentration of all sites (114 ± 85 μg/m3) was 2.3 times higher than the Chinese National Ambient Air Quality Standard (NAAQS) (annual standard:35 μg/m3). The total PAH level was highest at traffic site (46.2 ± 21.4 ng/m3), followed by urban center site (40.1 ± 18.7 ng/m3), industrial site (38.8 ± 17.2 ng/m3), urban site (37.8 ± 10.3 ng/m3) and background site (34.0 ± 19.4 ng/m3) with an annual concentration of 39.1 ± 17.6 ng/m3 for all sites. The seasonal variation was in the order of winter > autumn > spring > summer. Among 16 PAHs, BbF, Ind, BkF, Chry, and BghiP were more abundant species with an integral trend of 5–6 rings > 4 rings > 2–3 rings. The annual BaP concentration (2.1 ng/m3) exceeded the limit of the annual average BaP (1.0 ng/m3) given by the NAAQS, and the BaPeq concentration was at a high level, which indicated a severe health risk of PAHs. The incremental lifetime cancer risk results showed that the risk level was acceptable level in the study area. Diagnostic ratios analysis demonstrated that PAHs in the study area were produced by the common outcome of the fossil fuel, petroleum, biomass, and coal combustions. Four sources determined by positive matrix factorization were coal combustion, motor vehicles, biomass burning, and industry, which respectively accounted for 37.9%, 26.9%, 19.7% and 15.4% of the annual total PAHs in Zhengzhou. The contribution of motor vehicles/aircraft fuel source was the highest at the traffic site (29.7%) and the contribution of industry was higher at industrial site (21.4%). The contribution of biomass burning in autumn was greater than that in other seasons because open burning of straws increased during harvest season while the contribution of coal combustion increased in winter due to concentrated heating.