This paper reviews international research trends on per- and polyfluoroalkyl substances (PFAS) transport mechanisms and numerical modeling in subsurface environments. PFAS transport is governed by complex retardation mechanisms including non-equilibrium sorption, air-water interface (AWI) adsorption, and competitive sorption, with dynamic behavior associated with varying moisture conditions particularly in the vadose zone. Numerical models for simulating these processes have evolved from simple equilibrium-sorption-based approaches to multi-process rate-limited mass-transfer (MPMT) models. Representatively, HYDRUS effectively captures complex transport phenomena in the vadose zone by coupling a proven numerical platform with a PFAS-specific AWI module, MPMT-based models provide the most sophisticated interpretation of diverse retardation mechanisms through continuous model updates, and MODFLOW-based models are well-suited for comprehensive groundwater flow system analysis at site and watershed scales. Analysis of scale-dependent modeling studies reveals that the dominant factors controlling PFAS transport vary distinctly with scale: mass transfer limitations within thin water films at the pore scale, non-equilibrium sorption-desorption kinetics and competitive adsorption at the laboratory scale, and partition coefficients and hydrogeological characteristics at the field scale. Domestic PFAS research has focused primarily on treatment technologies, toxicity assessment, and contamination surveys, leaving subsurface transport modeling research at an early stage. Future research efforts should address the development of transport parameter databases suitable for domestic soil conditions, site-scale modeling studies reflecting source-specific characteristics, and methodologies for upscaling laboratory-scale parameters to field scales. This paper aims to contribute to the advancement of domestic research through a systematic review of PFAS transport mechanisms and numerical modeling.

Keywords: PFAS Transport, Numerical modeling, Retardation Mechanism, Air-water Interface Adsorption, Subsurface Environment