Phthalate esters in atmospheric PM2.5 at Mount Tai, north China plain: Concentrations and sources in the background and urban area

Atmospheric PM_2.5-bound Phthalate esters (PAEs) pose a major threat to human health. We investigated the concentrations and sources of PAEs in the background and urban area by sampling at the top and foot of Mount Tai (MT_top and MT_foot) from May 12 to June 24, 2017. Results demonstrated that the total concentrations of PAEs at the MT_top (120.17 ± 224.37 ng m^-3) and MT_foot (130.38 ± 129.01 ng m^-3) were close to the domestic urban pollution levels. Di-n-butyl phthalate (DnBP) and bis (2-ethylhexyl) phthalate (DEHP) showed high abundances during the whole sampling period. Daytime PAEs concentrations were higher than that in nighttime both at the MT_top and MT_foot, which is associated with anthropogenic activities, planetary boundary layer (PBL), ambient temperature, and inversion layer. PAEs concentrations were affected by the amount of rainfall. Furthermore, we identified the sources of PAEs based on meteorological conditions and backward trajectories. Dimethyl phthalate (DMP) and DEHP were mainly from the long-range transport of the high-altitude air masses passed through Shanxi and Hebei provinces in the north direction, especially at the MT_top. Diethyl phthalate (DEP), DnBP and di-n-octyl phthalate (DnOP) were mostly transported from the urban area in the south direction to the MT_top. The sufficiently high PBL, small wind speeds and south-westerly winds were the necessary conditions in the local transport. These findings will help in understanding of PAEs pollution characteristics and provide a scientific basis for reducing PAEs pollution in North China Plain (NCP).