2.4. Quality assurance and quality control (QA/QC)QA/QC was conducted by performing method blanks, standard reference material recoveries and standard spiked recovers. A method blank, blank glass fiber filters and duplicate were processed in the same way as the samples and analyzed in parallel with each batch of 10 samples, the variation coefficient of PAHs concentrations between duplicate samples was b10%. Standard spiked recovers were processed with adding known standard substance to blank fibers to get the recoveries and the standard reference material were operated with introducing known standard substance to sample fibers to obtain the reference data. Only a few lower molecular weight (LMW, 2 and 3 ring PAHs) PAHs were discovered in the blank glass fiber filters. The mean recoveries for standards in field samples were ranged from 61% (Py) to 126% (Nap) and all the PAHs concentrations reported in this paper were corrected for the recovery efficiency and blanks. The method detection limit of each PAHs species was shown in Table S2.