Pollution Characteristics Of Polycyclic Aromatic Hydrocarbon In Atmospheric Particulate Matters And Surface Soils Of Kunming City

With the expansion of city scale and rapid development of urbanization, air quality has become a significant societal problem over the world, and particulate matter has become the primary influence factors of ambient air quality. Polycyclic aromatic hydrocarbons (PAHs) are a typical class of persistent organic pollutants (POPs) due to their high toxicity, persistence and carcinogenic/mutagenic human health impacts. Coupled with ubiquitous distribution in the ambient environment, growing attention is being paid to PAHs. Additionly, PAHs are favorable to adsorb on inspirable particlelate matter, and both of them can penetrate into the deeper area of the lung, directly affect the respiratory surfaces and dissolve into blood which may cause systemic toxic effects. In this paper, the concentrations, distribution, possible sources and cancer risks of polycyclic aromatic hydrocarbons (PAHs) in particulate matters and surface soils collected from seven sampling spots (including six national ambient air monitoring sites of Kunming City) were analyzed in Kunming, China. Mainly to obtain the following conclusions:(1) In 2012, the daily average concentration of TSP was 331.23 μg/m3, and the daily average concentration of TSP and PM2.5 were 251.21 μg/m3 and 34.25 μg/m3 in 2014, respectively. The ratio of PM2.5/TSP concentrations was low, which might be because of higher contributor of re-suspension of particle to TSP concentrations in spring. The air quality of Kunming is good on a national scale, but the concentration of TSP was higher than national secondary standard. Atmospheric pollution problems have appeared in Kunming, and we need to strengthen comprehensive pollution control.(2) In 2012, the total PAH concentrations were 9.35-75.01 ng/m3 and 101.64-693.30 ng/g dry weight (d.w.), respectively, in TSP and surface soils. And in 2014, the total PAH concentrations in TSP, PM2.5 and surface soils were 18.50-47.18 ng/m3,7.67-26.49 ng/m3 and 72.16-442,40 ng/g d.w., Compared to other domestic cities, the levels of PAH in Kunming were lower than that in northern cities of China, and similar or higher than southern cities.(3) The spatial distribution of PAHs in TSP is closely related to the surrounding environment, which varied significantly as a result of variations in sources emission and changes in meteorology. However, the spatial distribution of PAHs in surface soils is supposed to correlate with a city’s urbanization history, and high levels of PAHs were always observed in industry district, central or old district of city.(4) Fluoranthene (FLA), pyrene (PYR), chrysene (CHR), phenanthrene (PHE) and benzo[b]fluoranthene (BbF) were the abundant compounds in TSP, PM2.5 and surface soil samples. And the proportion was higher than 60%, which indicating that PAHs might have similar patterns of source emissions.(5) The diagnostic ratios and principal component analysis (PCA) identified that the pyrogenic origins were the main sources of PAHs in particulate matters and surface soils, especially coal, liquid fossil fuel and wood combustion. And petroleum sources may exist in certain sample sites.(6) In 2012, the toxic equivalent concentrations of PAHs (BaPeq) were 1.16 ng/m3 and 49.77 ng/g d.w., respectively, in TSP and surface soils. And in 2014, the BaPeq concentrations in TSP, PM2.5 and surface soils were 1.93 ng/m3,1.25 ng/m3 and 17.64 ng/g d.w.. The BaPeq concentrations in PM2.5 accounted for 65% of those in TSP, which indicated that high carcinogen PAHs were predominantly sorbed onto fine particulates. In both the particulate and surface soil samples, DaA, BaP, BbF and BaA contributed more than 80% of the total carcinogenic potential of the PAHs, and more attention should be paid to these compounds to reduce the potential risk for human health. The incremental lifetime cancer risk (ILCR) exposed to PAHs in TSP ranged from 10"6 to 10-4 indicating potential of carcinogenic risk, and that in PM2.5 were 10-4 indicating high potential of carcinogenic risk. The ILCR exposed to soil PAHs was from 10-8 to 10-6 indicating virtual safety. These presented results showed that particle-bound PAHs had higher potential carcinogenic ability for human than soil PAHs. And the values of cancer risk for children were always higher than for adults, which demonstrated that children were sensitive to carcinogenic effects of PAHs. The dermal contact contributed a greatest proportion to the overall exposure, followed by ingestion and inhalation.