Plant Uptake of Per- and Polyfluoroalkyl Substances at a Contaminated Fire Training Facility to Evaluate the Phytoremediation Potential of Various Plant Species

Fire training facilities and other areas suffer from serious per- and polyfluoroalkyl substance (PFAS) contamination in soil, surface water, and groundwater due to regular practices with PFAS-containing aqueous firefighting foams (AFFFs). Therefore, the uptake of 26 PFASs in plants and the contamination of soil and groundwater has been investigated at a fire training site at Stockholm Arlanda airport, Stockholm (Sweden) in 2016. Elevated ∑₂₆PFAS levels were detected in soil and groundwater ranging from 16 to 160 ng g^-1 dry weight (dw) and 1200-34 000 ng L^-1, respectively. Samples from different plant species and tissues (i.e., roots, trunk/cores, twigs, leaves/needles) of the local plant community were taken, namely silver birch (Betula pendula), Norway spruce (Picea abies), bird cherry (Prunus padus), mountain ash (Sorbus aucuparia), ground elder (Aegopodium podagraria), long beechfern (Phegopteris connectilis), and wild strawberry (Fragaria vesca). The plants showed a high variability of concentrations with highest ∑₂₆PFAS concentrations in vegetative compartments with up to 97 ng g^-1 wet weight (ww) and 94 ng g^-1 ww in birch leaves and spruce needles, respectively. Annual ground cover plants such as long beechfern and ground elder, and bushes like bird cherry showed concentrations up to 6.9, 23, and 21 ng g^-1 ww, respectively. The bioconcentration factors (BCFs; plant/soil ratios) were highest in foliage, while the total tree burden of ∑₂₆PFASs per tree was up to 11 mg for birch and 1.8 mg for spruce. Considering a shelterwood system with mixed stands of silver birch and spruce in combination with regular harvest of leaves and birch sap and an understory of ground elder, it is potentially feasible to remove 1.4 g of ∑₂₆PFASs per year and hectare from (heavily) contaminated sites. An alternative approach is the coppicing of birch trees in combination with an understory of ground elder, potentially removing 0.65 g yr^-1 ha^-1 of ∑₂₆PFASs, while a simple meadow with ground elder can remove 0.55 g yr^-1 ha^-1 ∑₂₆PFASs.