Greenhouse-Scale Comparison of 10 Native Pacific Northwest Plants for the Removal of Per- and Polyfluoroalkyl Substances from Stormwater

Phytoremediation has the potential to remove per- andpolyfluoroalkylsubstances (PFAS) from stormwater. However, there is currently limitedknowledge as to how plant type affects PFAS removal from stormwater,particularly in plants commonly used in stormwater bioswales. Thisgreenhouse study evaluated the abilities of ten different PacificNorthwest native plants to remove PFAS from stormwater. The PFAS includedC4-C10 perfluoroalkyl carboxylates; C4, C6, and C8 perfluoroalkylsulfonates; and C6 and C8 perfluoroalkyl sulfonamides (FASAs). Plantswere irrigated with the contaminated stormwater once a week for 10weeks. The presence of plants enhanced PFAS removal over the uncultivatedcontrols, with rushes and dicots having the highest total PFAS removalefficiencies ranging from 75 to 80%. The fate of the PFAS compoundswas ultimately controlled by their Log organic carbon/water partitioncoefficient (K (oc)) and molar volume. ThePFAS molar volume and Log K (oc) were stronglycorrelated with soil affinity (Pearson's r = 0.82 to 0.85), resulting in greater removal efficiencies of largerPFAS compounds. Conversely, molar volume and Log K (oc) values were strongly negatively correlated with bioconcentrationfactors (BCFs)(Pearson's r = -0.72to -0.82), resulting in the preferential bioaccumulation ofsmaller PFAS compounds. PFAS molar volume was also strongly negativelycorrelated with plant translocation factors (TFs)(Pearson's r = -0.88), resulting in a preferential accumulationof the smaller PFAS compounds in the above-ground biomass. Conversely,root BCFs were positively correlated with the PFAS molar volume andLog K (oc) for C4-C7 compounds (Pearson's r = 0.91 to 0.96) but became negatively correlated for C8-C10compounds (Pearson's r = -0.89 to -0.99)as competition for sorption with the surrounding soil increased. Theresulting chevron pattern indicated that the plant roots preferentiallyaccumulated those PFAS compounds that were too large and hydrophobicto easily translocate to the above-ground biomass but were also toosmall and hydrophilic to have a strong affinity for the surroundingsoil. Mass recovered for C6 and C8 FASAs was & LE;35% in all plantsand uncultivated control, indicating microbial transformation. Enrichmentof linear perfluorooctane sulfonate (L-PFOS) was observed in all plantcomponents (leaves, stems, and roots) relative to the stormwater influent.Finally, the removal of PFAS compounds from the stormwater could beaccurately modeled with a multivariate linear regression containingthe PFAS Log K (oc). Additional multivariatemodeling revealed that plants with higher evapotranspiration rateshad higher PFAS accumulations. However, evapotranspiration rates alonecould not accurately model plant PFAS accumulation, indicating thatother factors are also responsible for the differences observed. Inparticular, evapotranspiration rates were not successful in predictingplant PFBA accumulation. Rather, PFBA accumulation increased withincrease in root mass, TFs, and leaf BCFs. This suggested that carrier-mediatedtransport mechanisms were responsible for PFBA accumulation in plants.