Watershed scale PFAS fate and transport model for source identification and management implications

Area of Science:

• Environmental Science
• Hydrogeology
• Environmental Chemistry

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent environmental contaminants requiring regional-scale fate and transport understanding for effective remediation.
• Perfluorooctane sulfonic acid (PFOS) is a prevalent long-chain PFAS of concern in soil, groundwater, and surface water.

Purpose of the Study:

• To develop and apply a distributed hydrogeochemical model for simulating PFOS fate and transport across a large watershed.
• To quantify PFOS movement from the unsaturated zone to groundwater and surface water through various pathways.
• To identify key factors influencing PFOS release from diverse sources, including urban, agricultural, and industrial areas.

Main Methods:

• Development of a distributed hydrogeochemical model.
• Application of the model to a large-scale watershed with multiple PFOS sources.
• Analysis of spatiotemporal PFOS concentrations and transport pathways (leaching, surface runoff, lateral flow, sediment transport).

Main Results:

• The model successfully reproduced the spatiotemporal PFOS concentrations in the watershed.
• Surface runoff emerged as a significant PFOS transport pathway, particularly from urban and industrial sites.
• Sediment transport, especially from sites with biosolids application, was identified as a notable release pathway.
• Topography, soil water retention, and water-solid adsorption were critical factors influencing PFOS transport dynamics.

Conclusions:

• The developed model provides a valuable tool for understanding and predicting PFOS fate and transport at the watershed scale.
• Identifying key transport pathways and influencing factors enables better source identification and targeted management strategies for PFOS contamination.
• This research supports the development of strategic plans for PFAS remediation and mitigation.