HYDROGEOCHEMICAL ANALYSIS AND MODELLING OF GROUND WATER IN MBEERE SOUTH SUB-COUNTY, EMBU COUNTY, KENYA STELLA KAREGI PETER I56/32257/2015 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF MASTER OF SCIENCE IN THE SCHOOL OF PURE AND APPLIED SCIENCES, KENYATTA UNIVERSITY FEBRUARY, 2020 ii DECLARATION This thesis is my original work and has not been presented for a degree or other awards in any other university. Signature Date Stella Karegi Peter Department of Chemistry Kenyatta University This thesis has been submitted with our approval as University supervisors Signature Date Dr. G. Kibe Macharia Department of Chemistry Kenyatta University Signature Date Dr. Wachira Muthengia Department of Physical Sciences University of Embu iii DEDICATION I dedicate this work to my loving husband, John Kariuki, my sons; Muriithi, Mutugi and Muthomi and finally to my parents, late Peter and Dionisia. iv ACKNOWLEDGEMENTS First and foremost, I sincerely thank my supervisors, Dr Kibe Macharia from Kenyatta University and Dr Wachira Muthengia from University of Embu for their guidance, assistance and encouragement during my research. Their positive comments and personal involvement in the preparation of this thesis is immensely appreciated. My colleagues and friends; James Ringa Kapis Otieno, Peter Karoki, Josphine Mwihaki and Davice Abuna are also highly appreciated for their encouragement, warm academic company and consultations during this work. I acknowledge the Department of Chemistry, Kenyatta University, Water Resource Authority (WRA) Embu and Department of Physical Sciences, University of Embu for allowing me use their research laboratories and instruments during this study. Many thanks go to Kenyatta University administration for according me admission into this Masters’ program. The Ministry of Education Science and Technology through African Development Bank is also highly appreciated for the M.Sc. scholarship. I am very grateful to technical staff, Simon Mukono, Catherine Njeru and David Kariuki for their guidance during laboratory analysis. I sincerely give the Almighty God all glory for granting me sound health, strength, and determination to undertake this study. v TABLE OF CONTENTS DECLARATION .......................................................................................................... ii DEDICATION ............................................................................................................. iii ACKNOWLEDGEMENTS ......................................................................................... iv TABLE OF CONTENTS ...............................................................................................v LIST OF TABLES ....................................................................................................... ix LIST OF FIGURES ..................................................................................................... ix ABBREVIATIONS AND ACRONYMS .................................................................... xi ABSTRACT ................................................................................................................ xii CHAPTER ONE ............................................................................................................ i INTRODUCTION .........................................................................................................1 1.1 Background ......................................................................................................... 1 1.2 Problem Statement .............................................................................................. 3 1.3 Justification ......................................................................................................... 4 1.4 Research Questions ............................................................................................. 5 1.5 Hypothesis ........................................................................................................... 6 1.6 Objectives ............................................................................................................ 6 1.6.1 General Objective ........................................................................................ 6 1.6.2 Specific Objectives ...................................................................................... 6 1.7 Significance of the Study .................................................................................... 6 1.8 Scope and Limitation of the Study ...................................................................... 7 CHAPTER TWO ...........................................................................................................8 LITERATURE REVIEW ..............................................................................................8 2.1 Hydrogeochemistry of Groundwater ................................................................... 8 2.2 Factors Affecting Hydrogeochemistry of Groundwater .................................... 10 2.3 Water Type Systems .......................................................................................... 12 2.4 Physicochemical Characteristics of Groundwater ............................................. 13 2.5 Diseases Caused by Polluted Water .................................................................. 14 vi 2.6 Irrigation Water Quality .................................................................................... 14 2.7 Modeling of Groundwater ................................................................................. 18 2.7.1 PHREEQC Program .................................................................................. 19 2.7.2 Forward Geochemical Modelling .............................................................. 21 2.7.3 Inverse Geochemical Modelling ................................................................ 22 2.7.4 Transport Geochemical Modelling ............................................................ 23 2.8 Analytical Techniques ....................................................................................... 24 2.8.1 Electrochemical Methods .......................................................................... 24 2.8.2 Spectrometric Methods .............................................................................. 24 2.8.3 Atomic Absorption Spectroscopy (AAS) .................................................. 24 2.8.4 UV-VIS Spectroscopy ............................................................................... 25 CHAPTER THREE .....................................................................................................27 MATERIALS AND METHODS .................................................................................27 3.1 Research Design ................................................................................................ 27 3.2 Study Area ......................................................................................................... 28 3.2.1 Topography ................................................................................................ 30 3.2.2 Geology ..................................................................................................... 30 3.2.3 Soils ........................................................................................................... 30 3.2.4 Social Economic Activities ....................................................................... 31 3.2.5 Water Resources ........................................................................................ 32 3.2.6 Rainfall ...................................................................................................... 32 3.3 Water Sampling Locations ................................................................................ 33 3.4 Sampling and Field Analysis ............................................................................. 33 3.4.1 Sample Pre-treatment ................................................................................ 34 3.5 Sample Laboratory Analysis ............................................................................. 34 3.5.1 Determination of Potassium and Sodium .................................................. 35 3.5.2 Determination of Iron ................................................................................ 35 3.5.3 Determination of Chloride ......................................................................... 36 3.5.3.1 Potassium Chromate Indicator ............................................................... 36 3.5.3.2 Silver Nitrate Solution ........................................................................... 36 3.5.3.3 Sodium Chloride Solution...................................................................... 36 3.5.4 Determination of Fluoride ......................................................................... 37 3.5.5 Determination of Calcium and Magnesium ............................................... 38 3.5.6 Determination of nitrate ............................................................................. 38 vii 3.5.7 Determination of Carbonates and Bicarbonates ........................................ 39 3.5.8 Determination of Sulphate Ions ................................................................. 40 3.6 Modelling .......................................................................................................... 41 3.7 Data Analysis ...................................................................................................