DISSERTATION Groundwater Contaminant Source Zone Identification at an Industrial and Abandoned Mining Site – A Forensic Backward-In-Time Modelling Approach Submitted to the faculty of Natural Sciences III of the Martin Luther University Halle-Wittenberg In partial fulfilment of the requirements for the award of the degree of Doctor of Natural Sciences By Dipl.-Geol. Reiner Stollberg Born on: 05-12-1981 in Wolfen, Germany Committee: 1. Prof. Dr. rer. nat. Peter Wycisk 2. Prof. Dr. rer. nat. Holger Weiß 3. Prof. Dr. rer. nat. Rudolf Liedl Submitted: Halle (Saale), 25-04-2012 Date of Defence: Halle (Saale), 28-01-2013 “All models are wrong but some are useful” George E. P. Box Declaration of Authorship I, Reiner Stollberg hereby declare that this thesis and the work presented in it are entirely my own and have been generated by me as the result of my research. All the sources I have used or quoted are signed clearly by means of complete references. Sign: Date: 25-04-2012 Acknowledgment It is a pleasure to thank the many people who contributed to make this thesis possible. First of all, I would like to thank my supervisors Prof. Dr. Peter Wycisk, Martin Luther University Halle-Wittenberg, and Prof. Dr. Holger Weiß, Helmholtz Centre for Environmental Research – UFZ, for their assistance and guidance during my research as well as for their trust and confidence to bring this thesis to a successful conclusion. This bilateral supervision has been carried out in the frame of a HIGRADE sholarship granted by the Helmholtz Centre for Environmental Research – UFZ of the Helmholtz Association. I would like to show gratitude to my advisor Dr. habil. Wolfgang Gossel of the Martin Luther University Halle-Wittenberg for his experiences on modelling he shared with me, the numerous discussions, comments, and his professional support throughout my whole Ph.D. time. With his inspiration and enthusiasm he kept me motivated from the beginning to the concluding level of the thesis, even in tough times. He is a brilliant tutor for students as well as for young scientists, and I am thankful for the excellent teaching content and working material he offered me. I am indebted to my many student colleagues for providing a pleasant and creative working atmosphere as well as a fun environment. Therefore, I am especially grateful to Thomas Müller, Ronny Lähne, and Christian Wolfig who never grew tired concerning discussions and sudden inspirations even late at night. A special thanks goes to Ralf Trabitzsch who helped me at all times with his organisation talent on formal urgent matters, on those I was too wearied to clarify or arrange myself. I owe my deepest gratitude to my parents, grandmothers, and my sister who supported and encouraged me in pursuing my career. Without them, this would have been impossible. Not to forget my close friends, who I really would like to thank for their support as well as the needed distraction during the hard times. They have always believed in me. Lastly, I offer my regards and blessings to all of those I did not mention here, who supported me in any respect during the completion of the project. Table of Contents ABSTRACT ............................................................................................................................................ I KURZFASSUNG ................................................................................................................................... II LIST OF FIGURES ............................................................................................................................. III LIST OF TABLES................................................................................................................................ IX LIST OF SYMBOLS AND ABBREVIATIONS .................................................................................. X 1 INTRODUCTION ......................................................................................................................... 1 1.1 Introduction to forensic modelling ......................................................................................................... 1 1.2 Purpose and aim of the study ................................................................................................................ 2 1.3 Previous work ....................................................................................................................................... 3 2 CASE STUDY AREA: BITTERFELD‐WOLFEN ...................................................................... 5 2.1 Regional Classification ........................................................................................................................... 5 2.1.1 Climate ................................................................................................................................................... 5 2.1.2 Surface Waters ....................................................................................................................................... 6 2.1.3 Geomorphology ................................................................................................................................... 10 2.1.4 Geological Settings .............................................................................................................................. 12 2.1.5 Hydrogeological Settings ..................................................................................................................... 20 2.2 History of lignite mining ...................................................................................................................... 24 2.3 Industrial history and production ......................................................................................................... 28 2.4 Environmental impacts from mining and industry ................................................................................ 31 2.5 Chapter summary ................................................................................................................................ 36 3 FORENSIC MODELLING – NUMERICAL APPROACHES ................................................ 37 3.1 Groundwater flow modelling ............................................................................................................... 37 3.1.1 Fundamentals on groundwater modelling .......................................................................................... 38 3.1.2 3‐D groundwater flow model .............................................................................................................. 39 3.2 Transport modelling (forward‐in‐time) ................................................................................................. 42 3.2.1 Solute transport mechanisms .............................................................................................................. 42 3.2.2 3‐D transport model ............................................................................................................................ 48 3.3 Forensic transport modelling (backward‐in‐time) ................................................................................. 51 3.3.1 Reverse particle tracking ..................................................................................................................... 52 3.3.2 Backward‐in‐time transport modelling ................................................................................................ 57 3.4 Chapter summary ................................................................................................................................ 60 4 NUMERICAL APPLICATION AND SIMULATION ............................................................. 62 4.1 Finite element method (FEM) .............................................................................................................. 62 4.2 Generic simulations in 2‐D transient flow fields ................................................................................... 65 4.2.1 Problem definition ............................................................................................................................... 65 4.2.2 Transient flow simulation (forward‐in‐time) ........................................................................................ 66 4.2.3 Transient transport simulation (forward‐in‐time)................................................................................ 69 4.2.4 Reverse particle tracking (backward‐in‐time) ...................................................................................... 74 4.2.5 Backward‐in‐time transport modelling ................................................................................................ 79 4.2.6 Model accuracy and numerical stability .............................................................................................. 89 4.2.7 Chapter summary ................................................................................................................................ 92 4.3 The Bitterfeld‐Wolfen megasite: a 3‐D case study scenario under real‐world conditions ....................... 93 4.3.1 Problem definition ............................................................................................................................... 93 4.3.2 Spatial and temporal model discretisation .......................................................................................... 93 4.3.3 The structural model ..........................................................................................................................