Dynamic variations of phthalate esters in PM_2.5 during a pollution episode

Phthalate esters (PAEs) as hazardous air pollutants can be easily released during the life cycle of plastic products. In this study, a thermal desorption aerosol comprehensive two-dimensional gas chromatography mass spectrometer coupled with a dual-trap was developed and used to measure the hourly-resolved PAEs characteristics in atmospheric PM_2.5 at an urban site. Dimethyl phthalate (DMP), diethyl (DEP), dibutyl (DnBP), benzyl butyl (BBP), di(2-ethylhexyl) (DEHP), and di-n-octyl phthalate (DnOP) in PM_2.5 were analyzed. The most abundant compounds were DEHP and DMP, followed by DnBP and DEP. The mass concentrations of the detected PAEs are comparable to those at other urban sites measured using offline methods with a lower time resolution. The concentrations of PAEs showed intense change with the variation of PM_2.5 mass concentration. The proportion of DEHP increased while that of DMP decreased with the increase in PM_2.5 pollution. Positive correlations between PAEs and PM_2.5, organic carbon, and elemental carbon were observed, while PAEs had negative correlation with the ambient temperature. Our observation provides evidences on understanding the volatile and semi-volatile PAEs in the ambient aerosols.