By Abdelbagi Nasir Ahmed Elrashid

208 Pages·2016·3.97 MB·English

A Survey of Naturally Occurring Radioactive Nuclides
in Food Samples Collected From Nuba Mountains
West-Central Sudan (South Kordofan State)

A Thesis Submitted to University of Khartoum in Fulfillment of the
Requirements for the PhD Degree in Science (Radiochemistry)

By
Abdelbagi Nasir Ahmed Elrashid
B. Sc. in Education and Science (chemistry) University of Khartoum 1991
M. Sc. in Chemistry University of Khartoum 1999

Supervisor: Professor Mohamed Ahmed Hassan Eltayeb
Undersecretary of Sudanese Nuclear and Radiological Regulatory Authority

Co-Supervisor: Dr. Ibrahim Mukhtar Ahmed
Department of Chemistry Faculty of Education

October 2015
DEDICATION

I dedicate this thesis to the memory of my
father and my grandfather. To my mother,
sisters, brothers, and to all my relatives.

i
ACKNOWLEDGEMENTS

I am indebted most of all to my Supervisor Professor Mohammed Ahmed Hassan
Eltyab, and co-supervisor Dr. Ibrahim Mukhtar Ahmed for their support and
encouragement throughout this study.
I am extremely grateful to Professor Ibrahim Osman Director General of Atomic
Energy Commission of Syria (AECS) and Professor Mohammed Saaed Elmasri
Head of radiation protection and safety section (AECS) for accepting to act as
external supervisors and for their encouragement, fruitful suggestions, generous
support throughout the course of this work, hospitality and to give me the chance
to do most of my work in radiochemistry laboratory at the department of radiation
physics, (AECS).
I wish to thank the staff in AECS, radiation protection and safety section for their
cooperation and creating a lovely work environment.
I wish to express my sincere gratitude and sincere thanks to Dr. Ali Hamoud Ali
for his constant guidance, support, motivation and untiring help during the course
of my project. His in-depth knowledge, valuable information and broad scientific
understanding as an expert in all disciplines of chemistry have been extremely
beneficial for me. He has given enough freedom during my research, and always
been nice.
I am under substantial intellectual debt to Professor Mustafa Mohammed Osman
Ahmed Sudan Atomic Energy Commission (SAEC), whose sustained interest,
assistance, stimulating discussions, constructive criticisms and scholastic
philosophy, I acknowledged him with special appreciation.
I am sincerely grateful to Dr. Khamal Khalifa Taha, for reading and commenting
upon the earlier versions of the thesis. His fruitful suggestions greatly improved
the quality of the final version.
ii
I am under substantial intellectual debt to the Professor Fathy Abdelraoof El
Khangi International Atomic Energy Commission (IAEA), who sustained interest,
assistance, stimulating discussions, constructive criticisms and scholastic
philosophy, I acknowledged him with special appreciation.
There are many persons who scarified much to make, even in the most difficult
circumstances that the institutional co-operation work. I so much respect those
efforts from Professor Omer Ibrahim El-Amin (SAEC), professor Ibrahim
Abdelrahim Shaddad (IAEA). and professor Adam Khatir Sam (IAEA),
Department of Nuclear Sciences and Applications, Monaco, France.
Many thanks to my friends and colleagues in SAEC, and especially Dr.
Mohammed Abdassalam Eltahir Director General, SAEC, who assisted me during
sample collection and preparation.
Not the least, I extend many thanks to all those who positively contributed to my
learning and to this research. For their names, I symbolically leave this space …,
and my sincere gratefulness.
Finally I would like to thank the faculty of education, Omdurman Islamic
University for giving me the chance to do my Ph.D. studies, especially Mr.
Mohammed Abdelrahman Eltyab.

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TABLE OF CONTENTS

Dedication i
ACKNOWLEDGMENTS ii
TABLE OF CONTENTS iv
LIST OF TABLES xi
LIST OF FIGURES xiv
ABSTRACT (English) xvi
ABSTRACT (Arabic) xviii
1. INTRODUCTION 1
1.1 Food analysis 1
1.2 Trace elements 1
1.2.1 Classification of elements 3
1.2.1.1 Macro nutrients 3
1.2.1.2 Micro nutrients 3
1.2.2 Sources of trace elements 3
1.2.2.1 Plants 4
1.2.2.2 Water 4
1.2.2.3 Soil 6
1.2.3 Trace elements requirements 8
1.2.4 Physiology of mineral elements 8
1.2.4.1 Calcium 8
1.2.4.1.1 Absorption and excretion 9
1.2.4.1.2 Toxicity 9
1.2.4.1.3 Deficiency 9
1.2.4.2 Potassium 9
1.2.4.2.1 Deficiency 10
1.2.4.3 Magnesium 10
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1.2.4.3.1 Absorption 10
1.2.4.3.2 Deficiency 10
1.2.4.4 Sodium 11
1.2.4.4.1 Absorption and excretion 11
1.2.4.4.2 Deficiency 11
1.2.4.5 Phosphorous 11
1.2.4.5.1 Absorption 12
1.2.4.5.2 Deficiency 12
1.2.4.6 Bromine 12
1.2.4.7 Cobalt 12
1.2.4.7.1 Absorption 13
1.2.4.7.2 Deficiency 13
1.2.4.8 Copper 13
1.2.4.8.1 Deficiency 13
1.2.4.9 Iron 13
1.2.4.9.1 Absorption 14
1.2.4.9.2 Iron deficiency 14
1.2.4.9.3 Toxicity 14
1.2.4.10 Manganese 14
1.2.4.10.1 Absorption and excretion 15
1.2.4.10.2 Deficiency 15
1.2.4.11 Lead 15
1.2.4.11.1 Absorption 15
1.2.4.12 Rubidium 15
1.2.4.13 Strontium 16
1.2.4.14 Zinc 16
1.2.4.14.1 Deficiency 16
1.2.4.15 Aluminum 16
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1.2.4.16 Titanium 17
1.2.4.17 Vanadium 17
1.2.4.18 Chromium 18
1.2.4.19 Arsenic 19
1.2.4.20 Selenium 20
1.2.4.21 Cadmium 21
1.2.4.22 Mercury 22
1.2.5 Factor effecting the trace element contents in food 23
1.2.5.1 Inherent factors 24
1.2.5.2 Environmental conditions 24
1.2.5.2.1 Geographical location 24
1.2.5.2.2 Fertilizers and fungicides 25
1.2.5.3 Effect of processing 25
1.2.6 Trace elements content in food 25
1.3 Environmental radioactivity 29
1.3.1 Introduction 29
1.3.2 Geochemistry of 238U, 232Th and their decay products 31
1.3.2.1 Geochemical associations 32
1.3.2.2 Influence of weathering 33
1.3.2.3 Geochemical cycles 36
1.3.2.4 Fractionation of uranium, thorium and their daughters 37
1.4 Analytical methods 39
1.4.1 Atomic absorption spectrometry 39
1.4.1.1 Principles 39
1.4.1.2 Instrumentation 41
1.4.2 X-ray fluorescence 42
1.4.2.1 Instrumentation 44
1.4.3 Neutron activation analysis (NAA) 44
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1.4.3.1 The basic principle of NAA 45
1.4.3.2 Cross sections 47
1.4.3.3 Radioactive decay 48
1.4.3.4 Half – life 49
1.4.3.5 Kinetics of activation 50
1.4.3.6 Experimental procedure 51
1.4.3.7 Irradiation facilities 51
1.4.3.8 Irradiation with neutrons 52
1.4.3.9 Measurement and evaluation 52
1.4.3.10 Analysis of the gamma spectra 54
1.4.3.11 Counting statistics 55
1.4.3.12 Methods of standardization 55
1.4.3.13 Absolute method 55
1.4.3.14 Classic relative method 56
1.4.3.15 Detection limits for NAA 57
1.4.3.16 Advantages and limitations of NAA 57
1.5 Environmental radioactivity measurements 58
1.5.1 Introduction 58
1.5.2 Interaction of nuclear radiation with matter 58
1.5 .3Instrumentation 59
1.5.4 Alpha-particle spectrometry 62
1.5.4.1 Optimization of source-detector separation 63
1.5.4.2 Data processing and analysis 64
1.5.5 Radiochemical separations 65
1.5.5.1 Basis of radiochemical separation procedure 66
1.5.5.1.1 Sample preparation 66
1.5.5.1.2 Preconcentration 66
1.5.5.1.3 Separation 67
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1.5.5.1.4 Source preparation 67
1.5.5.1.5 Counting stage 68
1.5.5.2 Special features of radiochemical analysis 68
1.5.5.2.1 Handling extremely small quantities of material 68
1.5.5.2.2 The use of carriers 69
1.5.5.2.3 Holding oxidants and reductants 69
1.5.5.2.4 The use of yield tracers 70
1.5.5.2.5 Adsorption of radioelements 71
1.5.5.2.6 Isotopic exchange 72
1.5.5.3 Separation methods 73
1.5.5.3.1 Precipitation and co-precipitation 73
1.5.5.3.2 Solvent extraction 75
1.5.5.3.3 Ion exchange 80
1.5.5.3.4 Electrode position 86
1.5.5.4 Review of separation chemistry of U, Th and Po 86
1.5.5.4.1 Uranium 86
1.5.5.4.2 Thorium 89
1.5.5.4.3 Polonium 90
1.6.5. Determination of uranium in environmental samples 91
1.6.5.1 Definitions 91
1.6.5.4.3 Applications 92
1.6.5.4.3 General principle 92
1.7 Objectives of the study 92
CHAPTER TWO: MATERIALS AND METHODS
2.1 Samples collection 93
2.2 Preparation of samples for analysis 93
2.2.1 Samples washing 93
2.2.2 Samples drying 93
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2.2.3 Destruction of the organic matter 93
2.2.3.1 Dry ashing 95
2.2.3.2 Wet digestion 95
2.3 Atomic absorption spectroscopy 96
2.3.1 Preparation of standard solutions 96
2.3.2 Calibration 96
2.3.3 Calculations 97
2.4 Uranium determination in environmental samples by fluorometer 97
2.4.1 Materials and apparatus 97
2.4.2 Reagents 98
2.4.3 Operating procedure 98
2.4.3.1 Soil and plant samples 98
2.4.3.2 Interference 100
2.4.3.3 Quality control 100
2.5 XRF measurements 101
2.6 NAA measurements 102
CHAPTER THREE: RESULTS AND DISCUSSION
3.1 Introduction 108
3.1.1 Study area 108
3.2 Measurements 110
3.2.1 AAS Measurements 110
3.2.2 NAA Measurements 114
3.2.2.1 Comparison between AAS and NAA 115
3.2.3 Polarography measurement 140
3.2.4 Fluorometery determination of uranium 141
3.3 Radioactivity measurements 142
3.3.1 Quality control procedures 142
3.3.2 Comparison between NAA and other techniques 142
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