Translocation and Tissue Distribution of Bisphenol AF and Its Transformation Products in Pumpkin Seedlings

Bisphenol AF (BPAF), a major alternative to bisphenol A, is frequently detected in the environment. However, the behavior of BPAF and its transformation products (TPs) in plants remains unclear. This study investigated the translocation and tissue distribution of BPAF and its TPs through a 168-h hydroponic exposure of BPAF. Over 95% of BPAF was transformed, yielding 40 identified TPs through complex transformation pathways. Desorption electrospray ionization mass spectrometry imaging and quantification data provided direct evidence that BPAF transformation primarily occurs in the root cortex and/or epidermis. TPs undergo both processes─being released into the hydroponic solution and translocated upward to stems and leaves. Distribution factors (DFs, concentration ratios of solution-root, stem-root, and leaf-stem) were calculated to elucidate their translocation patterns. A strong positive correlation between log K_ow and log DF_{solution-root} (Pearson's r = 0.944) suggested that passive diffusion mechanism dominates root release. In contrast, a negative correlation between log K_ow and log DF_{solution-root} (Pearson's r = -0.586) and a near-zero-equilibrium log DF_leaf-stem indicated that the acropetal translocation is mainly driven by xylem sap, with hydrophilic TPs exhibiting stronger potential to accumulate in leaves (even edible parts). These findings improve the understanding of the environmental behavior, fate, and associated risks of BPAF and its TPs.