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  • INCORPORATION OF NON-EQUILIBRIUM PARTITIONING OF PCBs INTO A

    MULTI-DIMENSIONAL TRANSPORT AND FATE MODEL

    A Thesis

    Presented to

    The Graduate School of

    Clemson University

    In Partial Fulfillment

    of the Requirements for the Degree

    Master of Science

    Civil Engineering

    by

    Savannah L. Hayes

    May 2015

    Accepted by:

    Dr. Abdul Khan, Committee Chair

    Dr. Earl Hayter

    Dr. Cindy Lee

  • ii

    ABSTRACT

    Equilibrium partitioning of contaminants has been a widely implemented

    assumption in transport and fate models. Challenges of this assumption began with

    Karickhoff et al. (1895) and continued with the work of Professor Wilbert Lick at the

    University of California, Santa Barbara and many others. These researchers and others

    have continued to show, through laboratory experiments and subsequent numerical

    models, that this assumption is not always valid. This is especially so for hydrophobic

    organic chemicals (HOCs) such as polychlorinated biphenyls (PCBs). The research of

    Karickhoff, Lick and many others provides evidence that HOCs can take up to 300 days

    to completely desorb from suspended sediments (Borglin et al., 1996) and about 150 days

    to reach equilibrium (Lick et al., 1997). Equilibrium models assume that the

    contaminants reach equilibrium over one model time step, which is often on the order of

    10 seconds or less.

    This thesis takes the non-equilibrium sorption models presented by Lick and

    others and incorporates them into a multi-dimensional transport and fate model within the

    Environmental Fluid Dynamics Code (EFDC), which is a widely used and EPA-accepted

    model. The results of verification tests show that contaminants can take up to 300 days to

    reach equilibrium for large particle sizes (250 m) and about 3 days for small particle

    sizes (25 m). Good agreement was found when a specific laboratory experiment by Lick

    (1997) was modeled with the non-equilibrium EFDC model.

    The model was then used to simulate the transport and fate of PCBs at a

    Superfund site in New Bedford Harbor, Massachusetts. The non-equilibrium model still

  • iii

    assumed PCBs in the dissolved organic carbon phase as well as PCBs in the sediment bed

    were in chemical equilibrium. Results from a one year simulation show a significant

    difference in water column concentrations, especially in the solids concentrations. These

    results indicate that the equilibrium partitioning model is underestimating the PCB solids

    concentrations. Based on the differences between the equilibrium and the non-

    equilibrium models the long term consequences of the equilibrium assumption could be

    significant. These conditions could dramatically change the PCB concentration

    predictions in marine biota from the similar predictions made with the equilibrium model.

    The biota PCB concentrations are an important parameter at the NBH Superfund project

    as well as other sites.

  • iv

    DEDICATION

    I would like to dedicate this work to my parents Jim and Jeanette Hayes for their

    support, love, encouragement, and funding throughout all of my life and throughout my

    two degrees. I would never have been able to achieve the things that I have without the

    skills and confidence that you have given me. I would also like to thank my fianc Nolan

    Lacy for being my rock, a shoulder to cry on, a cheerleader, an adviser, and the love of

    my life. I couldnt have done this without you.

  • v

    ACKNOWLEDGMENTS

    I would like to thank my adviser and mentor Dr. Hayter for encouraging me and

    guiding me through this adventure. He went above and beyond to make sure that I

    succeeded. I would like to thank the United States Army Corps of Engineers, Research

    and Development Center for funding my research and providing me with top of the line

    equipment. I would also like to thank Dr. Khan for believing in me from the start and

    giving me the confidence to pursue this degree. Thank you to Dr. Lee as well for

    providing recommendations and leading courses that better prepared me for this project

    and for my career.

  • vi

    TABLE OF CONTENTS

    Page

    TITLE PAGE .................................................................................................................... i

    ABSTRACT ..................................................................................................................... ii

    DEDICATION ................................................................................................................ iv

    ACKNOWLEDGMENTS ............................................................................................... v

    LIST OF TABLES ........................................................................................................ viii

    LIST OF FIGURES ........................................................................................................ ix

    CHAPTER

    I. INTRODUCTION ......................................................................................... 1

    Problem Statement .................................................................................. 2

    Goals and Objectives .............................................................................. 3

    New Bedford Harbor .............................................................................. 4

    II. LITERATURE REVIEW .............................................................................. 7

    Hydrophobic Organic Chemicals ............................................................. 7

    Hydrophobic Organic Chemical Desorption ........................................... 9

    New Bedford Harbor Equilibrium Model .............................................. 17

    III. NON-EQUILIBRIUM MODEL .................................................................. 24

    Non-Equilibrium Theory ....................................................................... 24

    Incorporation of Non-Equilibrium in EFDC .......................................... 30

    EFDC Non-Equilibrium Subroutines ..................................................... 31

    User Specified Parameters ..................................................................... 36

  • vii

    TABLE OF CONTENTS (Continued)

    CHAPTER Page

    IV. RESULTS and DISCUSSION ..................................................................... 38

    Verification Tests ................................................................................... 38

    Laboratory Simulation ........................................................................... 57

    New Bedford Harbor Simulations ........................................................ 62

    V. CONCLUSION and RECOMMENDATIONS...90

    APPENDICES ............................................................................................................... 95

    REFERENCES .............................................................................................................. 96

  • viii

    LIST OF TABLES

    Chapter Page

    1 Variables for Equations (2.6), (2.7), and (2.8) ............................................. 20

    2 Verification Tests Initial Conditions ............................................................ 39

    3 Test 4 Final Concentrations of Desorption from DOC ................................ 47

    4 Test 7 Final Concentrations of Adsorption to DOC .................................... 51

    5 Borglin et al. (1996) Verification Test Initial Conditions ........................... 59

    6 Table 6: NBH Simulation Non-Equilibrium Initial Conditions ................... 64

    7 Percent Difference in Maximum Concentrations in the Water Column ...... 68

    8 Percent Differences in Maximum Bed Concentration ................................. 69

    A-1 NOAA 18 PCB Congeners .......................................................................... 96

  • ix

    LIST OF FIGURES

    Figure Page

    1 New Bedford Harbor, Massachusetts ............................................................ 5

    2 New Bedford Harbor Model Domain (Hayter et al., 2014) ........................ 22

    3 Schematic of transport processes represented in the non-equilibrium model 25

    4 Contaminant Transport Subroutine Flowchart............................................. 31

    5 Diffusion from Bed to Water Column using 5 Layers ................................. 42

    6 Diffusion from Bed to Water Column using 1 Layer .................................. 42

    7 Diffusion from Water Column to Bed using 5 Layers ................................. 43

    8 Diffusion from Water Column to Bed using 1 Layer .................................. 43

    9 Desorption from Contaminated Suspended Sediments (250 m) ............... 45

    10 Desorption from Contaminated Suspended Sediments (25 m) ................. 45

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