Comprehensive Study of the Uptake, Transport, and Transformation Mechanisms of 6:2 Fluorotelomer Sulfonamidoalkyl Betaine (6:2 FTAB), a Novel PFOS Alternative, in Lettuce ( <i>Lactuca sativa</i> L.)

The environmental fate and underlying mechanisms of 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) in crops remain unclear. Herein, we revealed that 6:2 FTAB uptake in lettuce roots followed the Michaelis-Menten model and mainly occurred via an energy-dependent process involving anion channels and aquaporins through hydroponic experiments. 6:2 FTAB was primarily retained in root cell walls (72.1%) and trophoplasts (13.7%), with limited root-to-shoot transport driven by transpiration. 6:2 FTAB increased CYP450, ADH, ALDH, and GST activities by 1.1-3.6-fold, promoting its biotransformation in lettuce. Seven metabolites were identified, with 6:2 FTSA as the major product (75.4-88.4% of total metabolites). Density functional theory calculations assisted in elucidating the metabolic pathway of 6:2 FTAB, and transcriptomic analysis provided molecular evidence for the physiological and metabolic processes. These findings offer mechanistic insights into the environmental behavior of emerging PFASs in crops and valuable information for risk assessments related to food safety.