Assessing on toxic potency of PM2.5-bound polycyclic aromatic hydrocarbons at a national atmospheric background site in North China

•Collected PM2.5 samples at Tuoji Island were analyzed for PAHs.•High PAH concentrations were mainly in cold month.•Wheat straw burning was a major source of PAHs in June.•High toxic potency of PAHs in air were determined in middle Liaoning and south Shandong Peninsula.

A total of 76 PM2.5 samples collected at Tuoji Island from November 2011 to January 2013 were used to analyze 15 congeners of polycyclic aromatic hydrocarbons (∑15PAHs) and assess their toxic potency. The average ∑15PAHs was 15.34 ± 8.87 ng m− 3, ranging from 4.24 to 40.62 ng m− 3 over the sampling period. BkF, BbF, Phe and BaP were dominant PAH congeners, contributing together 60.64% of the ∑15PAH concentration. The highest monthly ∑15PAHs concentration was in January 2012, followed by the next January, which was closely four times greater than the lowest level occurred in July 2012. Wheat straw burning was responsible for the high PAH concentrations in June 2012. The averaged BaP toxicity equivalent (TEQ-BaP) concentration was 2.70 ± 1.88 ng m− 3 over the sampling period. BaP and DaA were the largest contributors, which contributed 58.5% and 14.7% of totals, respectively. The high TEQ-BaP and TEQ-BaP value per unit of ∑15PAHs concentration (TEQ-BaP(U)) values occurred in the cold season and the low levels presented in the warm period. The heaviest monthly TEQ-BaP was 5.28 ± 2.84 ng m− 3, which appeared in January 2012; the lowest value was 0.86 ± 0.33 ng m− 3, which occurred in July 2012. The potential source contribution function (PSCF) showed the occurrence of the high health risk associated with PAHs in the middle of Liaoning and the south of Shandong Peninsula.

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