Per- and polyfluoroalkyl substances (PFAS) in the Three-North Shelter Forest in northern China: First survey on the effects of forests on the behavior of PFAS

Per- and polyfluoroalkyl substances (PFAS) are a family of anthropogenic chemicals, that have attracted increasing attention since the early 2000 s. Although forests have been shown to act as a filter and important sink for nonpolar persistent organic pollutants (POPs), relevant reports on PFAS are lacking. Air, soil, and leaf samples were collected inside and outside the forest from two regions of the Three-North Shelter Forest in northern China between 2017 and 2018. Twenty-seven PFAS were analyzed to study the effect of forest on the transport and fate of PFAS. The average ratios of PFAS in the air outside to inside the forest (Q_air) ranged from 2.83 ± 0.78–10.6 ± 3.1. A significant positive correlation was found between Q_air and the n-octanol−air partition coefficient of individual PFAS (p = 0.041). Higher Q_air values for most ionic PFAS were found in broad-leaved forests than in coniferous forests. Soil samples outside the forests showed higher PFAS levels than those inside. The measured concentrations of 8:2 fluorotelomer alcohol, a volatile neutral PFAS, in leaf samples were two orders of magnitude higher than those estimated using the equilibrium leaf−air partition of nonpolar POPs, indicating that it may not fit the case of PFAS with surface activity.