Phosphogypsum (PG) stacks are traditionally assessed as sources of legacy inorganic contaminants, but the behavior of emerging contaminants in these chemically complex systems remains poorly understood. This opinion article proposes that PFAS, if present in PG stacks, may not be adequately described by partitioning concepts derived from dilute groundwater or ordinary soil porewater systems. Instead, the low-pH, high-ionic-strength, and calcium–sulfate-rich conditions of PG leachate may promote hydrochemistry-mediated repartitioning of PFAS. Under such conditions, PFAS may exhibit reduced apparent aqueous stability, enhanced association with PG particles or colloids, retention on particle surfaces, and enrichment at air–water interfaces, forming potential hidden reservoirs with the potential for delayed release and episodic remobilization. Consequently, dissolved concentrations alone may underestimate total PFAS storage and long-term groundwater risk in and around PG stack systems. Overall, this study highlights the need to shift from conventional dilute-system assumptions toward a hydrochemically mediated multiphase framework for PFAS occurrence assessment, monitoring design, and risk evaluation in phosphogypsum environments and other chemically complex industrial waste systems.
Du et al. (Wed,) studied this question.