Airborne particulate polycyclic aromatic hydrocarbon (PAH) pollution in a background site in the North China Plain: Concentration, size distribution, toxicity and sources

The size-fractionated characteristics of particulate polycyclic aromatic hydrocarbons (PAHs) were studied from January 2011 to October 2011 using a Micro-orifice Uniform Deposit Impactor (MOUDI) at the Yellow River Delta National Nature Reserve (YRDNNR), a background site located in the North China Plain. The average annual concentration of total PAHs in the YRDNNR (18.95 +/- 16.51 ng/m(3)) was lower than that in the urban areas of China; however, it was much higher than that in other rural or remote sites in developed countries. The dominant PAHs, which were found in each season, were fluorene (5.93%-26.80%), phenanthrene (8.17%-26.52%), fluoranthene (15.23%-27.12%) and pyrene (923%-16.31%). A bimodal distribution was found for 3-ring PAHs with peaks at approximately 1.0-1.8 mu m and 3.2-5.6 mu m; however, 4-6 ring PAHs followed a nearly unimodal distribution, with the highest peak in the 1.0-1.8 mu m range. The mass median diameter (MMD) values for the total PAHs averaged 1.404, 1.467, 1.218 and 0.931 mu m in spring, summer, autumn and winter, respectively. The toxicity analysis indicated that the carcinogenic potency of particulate PAHs existed primarily in the <1.8 mu m size range. Diagnostic ratios and PCA analysis indicated that the PAHs in aerosol particles were mainly derived from coal combustion. In addition, back-trajectory calculations demonstrated that atmospheric PAHs were produced primarily by local anthropogenic sources. (C) 2013 Elsevier B.V. All rights reserved.