March 2020 REVIEW OF MODELS FOR EVALUATING PER- AND POLYFLUOROALKYL SUBSTANCES IN LAND APPLIED RESIDUALS AND BIOSOLIDS An Assessment of Fate and Transport Models for Groundwater Leaching, Surface Water Runoff, and Plant Uptake REVIEW OF MODELS FOR EVALUATING PER- AND POLYFLUOROALKYL SUBSTANCES IN LAND APPLIED RESIDUALS AND BIOSOLIDS REVIEW OF MODELS FOR EVALUATING PER- AND POLYFLUOROALKYL SUBSTANCES IN RESIDUAL AND BIOSOLIDS An Assessment of Fate and Transport Models for Groundwater Leaching, Surface Water Runoff, and Plant Uptake Prepared by: Arcadis U.S., Inc. 410 N. 44th Street Suite 1000 Phoenix, AZ 85008 National Council for Air and Stream Improvement, Inc. 1512 Walnut Street, Suite 200 Cary, NC 27511 March 2020 arcadis.com REVIEW OF MODELS FOR EVALUATING PER- AND POLYFLUOROALKYL SUBSTANCES IN LAND APPLIED RESIDUALS AND BIOSOLIDS CONTENTS Acronyms and Abbreviations ........................................................................................................................ iv Executive Summary ................................................................................................................................. ES-1 Leaching Model Review .................................................................................................................... ES-2 Surface Water Runoff Model Review ................................................................................................ ES-3 Plant Uptake Model Review .............................................................................................................. ES-3 Summary ........................................................................................................................................... ES-4 1 Introduction ............................................................................................................................................. 1 1.1 Overview of PFAS in Residuals ...................................................................................................... 2 1.2 PFAS Fate and Transport ............................................................................................................... 3 1.2.1 Transport ............................................................................................................................. 4 1.2.2 Fate ..................................................................................................................................... 5 1.2.3 Key Fate and Transport Parameters for Modeling PFAS ................................................... 6 1.3 Model Screening and Review ......................................................................................................... 8 2 Leaching Model Review .......................................................................................................................... 9 2.1 Leaching Mechanisms .................................................................................................................... 9 2.1.1 Recharge and Advection ..................................................................................................... 9 2.1.2 Dispersion and Diffusion ..................................................................................................... 9 2.1.3 Hydrophobic Sorption (Koc) .................................................................................................. 9 2.1.4 Air-water interface partitioning (Kia) ................................................................................... 10 2.1.5 Electrostatic Adsorption ..................................................................................................... 10 2.1.6 Surfactant-induced Flow .................................................................................................... 10 2.1.7 Volatilization ...................................................................................................................... 11 2.1.8 Degradation ....................................................................................................................... 11 2.1.9 Summary and Considerations ........................................................................................... 11 2.2 Review of Selected Leaching Models ........................................................................................... 11 2.2.1 HYDRUS 1D, 2D, and 3D ................................................................................................. 12 2.2.2 HYDROGEOCHEM 4.0/5.0 ............................................................................................... 13 2.2.3 SVENVIRO™ (formerly SVCHEM and SVFLUX) ............................................................. 13 2.3 Leaching Model Summary and Recommendations ...................................................................... 14 arcadis.com i REVIEW OF MODELS FOR EVALUATING PER- AND POLYFLUOROALKYL SUBSTANCES IN LAND APPLIED RESIDUALS AND BIOSOLIDS 3 Surface Water Runoff Model Review .................................................................................................... 17 3.1 Runoff Mechanisms ...................................................................................................................... 17 3.1.1 Hydrophobic Sorption (Koc) ................................................................................................ 18 3.1.2 Air-Water Interface Partitioning (Kia) .................................................................................. 18 3.1.3 Electrostatic Adsorption (Kd) .............................................................................................. 18 3.1.4 Transformation Rates ........................................................................................................ 18 3.2 Review of Selected Runoff Models ............................................................................................... 19 3.2.1 Pesticide in Water Calculator – PRZM5 ............................................................................ 19 3.2.2 Pesticide in Water Calculator – Variable Volume Water Model ........................................ 20 3.2.3 Pesticide in Water Calculator Inputs ................................................................................. 20 3.3 Runoff Model Summary ................................................................................................................ 21 4 Plant Uptake Model Review .................................................................................................................. 23 4.1 Plant Uptake and Loss Mechanisms ............................................................................................ 23 4.1.1 Root Uptake ....................................................................................................................... 23 4.1.2 Transport from Roots to Other Plant Tissues .................................................................... 24 4.1.3 Vapor or Gas Uptake from Atmosphere ............................................................................ 25 4.1.4 Particle Deposition on Plant Surface ................................................................................. 25 4.1.5 Loss Mechanisms .............................................................................................................. 25 4.2 Review of Selected Plant Uptake Models ..................................................................................... 26 4.3 Soil-to-Plant Transfer Factors for PFAS ....................................................................................... 26 4.4 Plant Uptake Summary ................................................................................................................. 27 5 Summary and Conclusions ................................................................................................................... 29 5.1 Leaching ....................................................................................................................................... 30 5.2 Surface Water ............................................................................................................................... 30 5.3 Plant Uptake ................................................................................................................................. 31 5.4 Research Needs ........................................................................................................................... 31 6 References ............................................................................................................................................ 33 arcadis.com ii REVIEW OF MODELS FOR EVALUATING PER- AND POLYFLUOROALKYL SUBSTANCES IN LAND APPLIED RESIDUALS AND BIOSOLIDS TABLES Table 1 - Relative Importance of Parameters in Modeling PFAS Fate and Transport Table 2 - Review of Leaching Models for PFAS Table 3– Review of Surface Water Models for PFAS Table 4 - Review of Plant Uptake Models for PFAS FIGURES Exhibit 1. Primary Migration Pathways for PFAS in Land-Applied Residuals ............................................... 3 Exhibit 2. PFAS Families and Groups ........................................................................................................... 4 Exhibit 3. Relative Importance of Parameters in Modeling PFAS Fate and Transport ................................ 6 Exhibit 4. Key Input and Output Parameters for Leaching Pathway Models .............................................. 15 Exhibit 5. Key Input and Output Parameters for Surface Water Runoff Model