kinetics of trace metals sorption on and desorption from soils developing predictive models

KINETICS OF TRACE METALS SORPTION ON AND DESORPTION FROM SOILS: DEVELOPING PREDICTIVE MODELS by Zhenqing Shi A dissertation submitted to the Faculty of the University of Delaware in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering Winter 2006 Copyright 2006 Zhenqing Shi All Rights Reserved UMI Number: 3205426 3205426 2006 UMI Microform Copyright All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, MI 48106-1346 by ProQuest Information and Learning Company. KINETICS OF TRACE METALS SORPTION ON AND DESORPTION FROM SOILS: DEVELOPING PREDICTIVE MODELS by Zhenqing Shi Approved: __________________________________________________________ Michael J. Chajes, Ph.D. Chair of the Department of Civil and Environmental Engineering Approved: __________________________________________________________ Eric W. Kaler, Ph.D. Dean of the College of Engineering Approved: __________________________________________________________ Conrado M. Gempesaw II, Ph.D. Vice Provost for Academic and International Programs I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Herbert E. Allen, Ph.D. Professor in charge of dissertation I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Dominic M. Di Toro, Ph.D. Member of dissertation committee I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Chin Pao Huang, Ph.D. Member of dissertation committee I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Donald L. Sparks, Ph.D. Member of dissertation committee ACKNOWLEDGMENTS I express my greatest gratitude to many individuals who have helped and encouraged me to complete this dissertation. First and foremost, I wish to express my thanks to my advisor, Dr. Herbert E. Allen, for his guidance and encouragement not only in this study but also my professional career. I would have not been able to accomplish this research without his insightful advice and extraordinary support. The knowledge and experience I have learned is much more than what I had expected. I am very grateful to Dr. Dominic Di Toro who has guided me with most of the modeling work in the past three years. This research benefits a lot from his insight, broad vision and patient instructions. He leads me into the amazing world of computational environmental science. My appreciation is extended to other committee members, Dr. Chin Pao Huang, and Dr. Donald L. Sparks, and also to Dr. Alexander A. Ponizovsky for their assistance and invaluable advice during this study. Special thanks go to Dana Crumety for her continuous support throughout the past years. I also want to thank Doug Baker, Mike Davison and Eric Eckman for their technical assistance. I appreciate the US Environmental Protection Agency and International Copper Association for the financial support of the research. Additionally, many thanks are given to my friends and colleagues, Tao Cheng, Sagar Thakali, Dave Metzler, Vaishnavi Sarathy, Kevin Rader, Yuefeng Lu, iv and Yujun Yin, for their help. I also thank Dr. Steve Lofts, Centre for Ecology and Hydrology, Lancaster, United Kingdom, for his help on the WHAM VI program. Finally, my thanks and love are expressed to my dear parents, Qishuang Hou and Fuchu Shi, and my elder brother, Zhenshan Shi, who always encourage me and offer understanding in my journey of pursuing the doctoral degree. Wherever I go, they are always there to give me love and support. v v TABLE OF CONTENTS LIST OF TABLES ix LIST OF FIGURES x ABSTRACT xvii Chapter 1 INTRODUCTION 1 1.1 Background and Significance of the Study 1 1.2 Objective 6 References 9 2 LITERATURE REVIEW 12 2.1 Trace Metal Content in Soils and Reactivity 12 2.1.1 Copper 12 2.1.2 Zinc 13 2.1.3 Other Metals 14 2.2 Soil Properties Affecting Trace Metals Sorption and Desorption 16 2.2.1 Metal Concentration in Soils 16 2.2.2 Soil Organic Matter 18 2.2.3 Clay Minerals and Metal Oxides 20 2.2.4 Assessment of the Role of Different Soil Components 22 2.3 Solution Chemistry Affecting Trace Metals Sorption and Desorption 30 2.3.1 pH 30 2.3.2 DOM 32 2.3.3 Dissolved Calcium 34 2.3.4 Other Factors 35 2.4 Kinetic Behavior of Trace Metals Sorption and Desorption on Soils 36 2.5 Methods Used to Study Kinetics of Metal Sorption and Desorption on Soils 39 2.6 Modeling Kinetics of Metals Sorption and Desorption on Soil Particles 40 2.6.1 Kinetics Models Used for Metal Reactions with Soils 40 2.6.2 First-order Kinetic Equation 43 2.6.3 Two-site Model 45 2.6.4 Multi-site Model 48 2.6.5 Equilibrium Constraint for Kinetics Model 51 2.6.6 Theory and Modeling of Stirred-flow System 52 2.7 Conclusions on the Literature Review 54 References 56 3 MODELING METHODS 67 vi vi 3.1 Model Formulation 67 3.1.1 Reaction Chemistry 67 3.1.2 Basic Kinetics Model Formulations 70 3.1.3 Instantaneous Equilibrium (IE) Model 73 3.1.4 pH Dependency 75 3.1.5 Numerical Solutions for the Kinetics Model 77 3.2 Evaluation of the Kinetics Model 79 3.3 Obtaining Model Parameters 84 3.4 Relationship between Kinetics Model and Equilibrium Model 85 References 87 4 MODELING KINETICS OF CU AND ZN RELEASE FROM SOILS 88 4.1 Introduction 88 4.2 Materials and Methods 89 4.2.1 Chemicals and Samples 89 4.2.2 Soil Spiking 93 4.2.3 Stirred-flow Experiment 93 4.2.4 Experimental Matrix 97 4.3 Modeling Methods 98 4.4 Results and Discussion 99 4.4.1 Leaching Experiment 99 4.4.2 Modeling Zn Release Kinetics 115 4.4.3 Modeling Cu Release Kinetics 133 4.5 Model Tests and Assessments 145 4.6 Implications 151 References 158 5 AN ORGANIC CARBON NORMALIZED KINETICS MODEL TO PREDICT ZN SORPTION AND DESORPTION ON DIFFERENT SOILS 162 5.1 Introduction 162 5.2 Materials and Methods 164 5.2.1 Samples and Chemicals 164 5.2.2 Sorption and Desorption Kinetics Experiments 167 5.3 Model Description 168 5.4 Results and Discussion 170 5.4.1 Effect of Soil Properties 170 5.4.2 Effect of pH and Zn Loadings 183 5.5 Model Assessment and Implications 190 5.5.1 Evaluation of the Rate Coefficients 190 5.5.2 The Roles of Two Sites for Zn Sorption and Desorption Kinetics 191 5.5.3 Assessment of Model Simplifications and Limitations 198 References 205 vii vii 6 DEVELOPMENT OF THE PREDICTIVE MODEL FOR KINETICS OF CU SORPTION/DESORPTION ON SOILS 208 6.1 Introduction 208 6.2 Materials and Methods 210 6.2.1 Samples and Chemicals 210 6.2.2 Sorption and Desorption Kinetics Experiments 210 6.3 Model Description 211 6.3.1 Basic Model Formulation 211 6.3.2 Incorporation of Freundlich Equation 212 6.3.3 Incorporation of WHAM VI 217 6.4 Results and Discussion 220 6.4.1 IE Model 220 6.4.2 Freundlich Equation Based Kinetics Model 225 6.4.3 WHAM VI Based Kinetics Model 232 6.5 Model Assessment 251 6.5.1 The Role of Fe(III) and Al(III) 252 6.5.2 The Role of Active Organic Matter 257 6.5.3 The Effect of Ca 259 6.6 Other Metals 262 References 264 7 CONCLUSIONS AND RECOMMENDATIONS 266 Conclusions 266 Recommendations 269 Appendix A KINETICS MODEL FOR CU AND ZN RELEASE FROM TWO SOILS 272 A1 Zn Kinetics Model 272 A2 Cu Kinetics Model 275 B THE ORGANIC CARBON NORMALIZED ZN KINETICS MODEL 279 C WHAM VI BASED CU KINETICS MODEL 283 C1 General Information 283 C2 Instruction on Using the Computer Program 284 C3 Comments on the VB Code 285 C4 Definitions of Parameters in the EXCEL File 288 C5 Running the Model 290 viii viii LIST OF TABLES Table 2.1 Linear forms of kinetics equations (adapted from Sparks, 2003; detailed description of the symbols can be found in related literature) 41 Table 4.1 Soil characteristics 91 Table 4.2 Percent of Cu and Zn release at different pH and DOM concentrations in the 5-hour leaching experiment* 115 Table 4.3 Model fitting parameters for Zn release kinetics using kinetics model 127 Table 4.4 WHAM VI calculated K p at different pH 136 Table 4.5 Model fitting parameters for Cu release kinetics using kinetics model 138 Table 5.1 Soil properties 166 Table 5.2 Model parameters for different soils at pH 5.5 171 Table 5.3 Model parameters 178 Table 6.1 Model parameters for the Freundlich equation based kinetics model 232 Table 6.2 WHAM input parameters at pH 5.5 235 Table 6.3 Model fitting parameters for WHAM VI based kinetics model 235 Table A1 Definitions of Columns in EXCEL File Zn_Matapeake.xls 273 Table A2 Definitions of Columns in EXCEL File Cu_Matapeake.xls 276 Table B Definitions of Columns in EXCEL File Zn_OC.xls 280 Table C Definitions of Columns in EXCEL File Cu_WHAM.xls 288 ix ix [...]... Understanding the kinetics of trace metals sorption and desorption on soils is important for better prediction of metal behavior in the environment In this dissertation, the effect of solution chemistry and soil composition on trace metal sorption and desorption kinetics was investigated Based on the experimental results, predictive kinetics models were formulated and successfully used to describe the kinetics. .. based on equilibrium assumptions 1.2 Objective The objective of this study is to develop kinetics models to predict trace metals (mainly Cu and Zn) sorption and desorption on soil particles The effects of soil properties and solution chemistry on kinetics of trace metals sorption and desorption were studied Key soil and solution properties were selected The models are based on the minimal number of input... importance of soil sorbents for the binding of trace metals in soils 2.2.1 Metal Concentration in Soils The metal concentration in soils may directly affect both the amount and the rate of metals sorption and desorption The latter may be expected since the rate of any chemical reaction increases with the increase in the concentrations of reactants Moreover, the effect of metal concentration on the sorption and. .. re-adsorption on soils Among all soil components, soil organic matter (SOM) is the dominant phase controlling Cu and Zn sorption and desorption kinetics The effect of residence time was also tested xvii The kinetics models were formulated and successfully used to describe the Cu and Zn sorption and desorption kinetics under different solution chemistry and soil compositions The models are based on the... solutions (pore water) can become available to plants and animals in soils Both sorption and desorption processes are important for controlling the metal behavior in the soil and solution systems The sorption process directly affects the metal distribution among different soils components and thus the future desorption from soils The equilibrium of trace metals partition between soils and solutions has... anthropogenic sources of trace metals are mining and smelting, agricultural application of fertilizers, pesticides, and ameliorants containing trace metals, transportation, and municipal and industrial wastes Contamination of the environment with trace metals is a serious problem in many regions of the USA and all over the world Soils can sorb trace metals and provide an important source of trace metals to waters,... partition coefficient at every Cu loading The WHAM VI based kinetics model, which considered the nonlinear metal binding and heterogeneity of soils, successfully described Cu sorption and desorption kinetics for a variety of experimental conditions I expect that the models developed in this study can be used to predict trace metals xviii sorption and desorption kinetics under different solution chemistry... extensively and several equilibrium models have been developed to predict the partitioning of trace metals between solid and solution phases However, the sorption and desorption of trace metals on the soil particles appear to be a slow process and the equilibrium between solid and solution may not be attained in soils (Sparks, 1989 and 2001) There have been extensive equilibrium studies of metal sorption on soils. .. Affecting Trace Metals Sorption and Desorption Soils consist of different components including SOM, metal (hydro)oxides and clay minerals which are responsible for metal binding The extent of metal binding by these components is important for understanding the kinetics of metal reactions in soil systems Different components in soils may contribute to metal sorption and desorption to different extent... results of modeling the Cu and Zn 7 release from two soils, in which the effect of solution pH, DOM and flow rates are tested Chapter 5 develops a more general kinetics model for Zn sorption and desorption on different soils with the organic carbon normalization of sorption rate coefficients Chapter 6 focuses on incorporating the nonlinear Cu binding behavior and heterogeneity of SOM into the kinetics . Study Kinetics of Metal Sorption and Desorption on Soils 39 2.6 Modeling Kinetics of Metals Sorption and Desorption on Soil Particles 40 2.6.1 Kinetics Models Used for Metal Reactions with Soils. 48106-1346 by ProQuest Information and Learning Company. KINETICS OF TRACE METALS SORPTION ON AND DESORPTION FROM SOILS: DEVELOPING PREDICTIVE MODELS by Zhenqing Shi . KINETICS OF TRACE METALS SORPTION ON AND DESORPTION FROM SOILS: DEVELOPING PREDICTIVE MODELS by Zhenqing Shi A dissertation submitted to the Faculty of the