Fig. 4: PFAS partitioning in environmental media (log Kd).
The environmental sorption complex varies grossly with setting, with NOM concentrated in shallow soil horizons, and ferric (oxy)hydroxides commonly dominating in subsurface media (Properties). Log Kd varies as a function of fluoroalkyl number and terminal moiety (A (95); pH=5.2 values depicted). Because of this partitioning behavior, when not complicated by precursor degradation, i) relative mobility amongst PFAS commonly varies with fluoroalkyl carbon number (B (97),D (105),E (106)), ii) terrestrial vegetation accumulation diminishes with increasing fluoroalkyl number, but accumulation in terrestrial detrital feeders increases with fluoroalkyl number (C (101)), and iii) in aquatic settings, vegetative and detrital-feeder accumulation both increase with fluoroalkyl number (F (107)). CEC/AEC (cation-/anion-exchange capacity).