Investigation of input and distribution of polluting elements in Tinishu Akaki River, Ethiopia, based

221 Pages·2005·5.42 MB·English

Laboratory of Analytical Chemistry
Institute for Nuclear Sciences

Investigation of input and distribution of polluting elements
in Tinishu Akaki River, Ethiopia, based on the
determination by ICP-MS

Samuel Melaku Abegaz

Thesis submitted in fulfillment of the requirements for the degree of
Doctor of Philosophy (Ph.D.) in Science: Chemistry

Promoter: Prof. Dr. Luc Moens
Co-promoter: Prof. Em. Dr. Richard Dams

April 2005
This work is dedicated to my parents, sisters and brothers, for their
love, and endless support
Acknowledgements

I am very grateful to my promoter professor Dr. Luc Moens, the Dean of the Faculty of
Sciences, Gent University and my co-promoter professor Em. Dr. Richard Dams,
former Director of Laboratory of Analytical Chemistry, Gent University, for allowing
me to undertake my studies in the Institute for Nuclear Sciences, their support,
encouragement and invaluable guidance throughout the four years of my Ph.D. work.

Next, I am deeply grateful to my parents, Koyu Mekonnen and Melaku Abegaz, who
did not hesitate to sell their roof to support me financially. Without my parents;
sisters; Sahlemariam, Betemariam, Desta and Tsedi and brothers, Mulugeta, Fisseha
and Fikremariam, endless love, support and encouragement, I could not have
completed my Ph.D. study. My younger brother, Mulugeta, was also a great help with
the sampling.

I am very grateful for the financial support from Belgian Technical Co-operation,
BTC, and Laboratory of Analytical Chemistry, Gent University. I should also express
my appreciation to Mr. Thierry Coppin and Muriel Van Nuffel of BTC for their
efficient handling of my dossier over the years.

I would like to thank Dr. Taddese Wondimu for the handling of all administration
ups and downs related to my shipments, sharing his office and laboratory and his
friendship. I also would like to thank Christophe Collard for his nice work in
processing and preparing the figure of the study area from the various topographic
maps.

Special thanks are due to Rishan and Caroline for their sincere interest for helping me
in the administration formalities. My gratitude also goes to Prof. Dr. Karel
Strijckmans, the Director of Laboratory of Analytical Chemistry, Prof. Dr. Frank
Vanhaecke and Dr. Rita Cornelis for their willingness to discuss ideas related to my
topics and valuable suggestions.

The technical assistance and good friendship of R. Van Tittelboom, L. Mees, G.
Stevens, J. De Donder, R. Dolieslager J. Dewaele , M. Leys, and L. Mortier are
gratefully acknowledged.

Moreover, I would like to thank Mr. Teferi Zeleke, the head of Addis Ababa Water and
Sewerage Authority Laboratory, and his group for their help in major ions and
nutrients analysis. I owe a major debt of gratitude to Dr. Wondimagegn Mammo, Dr.
Tigistu Haile, Dr Kebede Oli, Dr. Gizachewu Alemayehu, Dr. Yonas Chebude, Dr.
Feleke Zewuge, Dr. Fasil Assefa, Dr. Dereje Ayalewu, Dr. Bekele Abebe, Dr. Tamiru
Alemayehu and Dr. Tarekegn G/Eyesus for their encouragement and assistance in so
many ways.

My sincere thanks also go to Chantal Hufkens and Ann Peters for their help in the
tedious administration issues and their good friendship. I take this opportunity to
thank all my fabulous friends Solomon Eshetu, Dr. Fre, Wondu, Abel, Jemi and Sele,
Tiru and Gedion, Mirt, Lulu, Bas, Eleni and Fisseha, Yegile, Bert, Dries, Jordy, Veerle,
Lieve, Evelien, Mura and Marlix, Almaz Beshiwork, Tigist Mola, Feti, Isabel, Rita
Ocskay, Jenny, Mire and the OBSG staffs for whatever other assistance was
requested and friendship, has been of great value to me.

Big thanks also go to all staffs of the Chemistry and Geology Department, Addis
Ababa University, Laboratory of Analytical Chemistry, Gent University and my
Ethiopian friends in Belgium.

Last but not least I wish to thank Els Cornelissen and her family, particularly Ria
and Jo for their friendship and help whenever needed.
Table of contents

Chapter 1. Introduction................................................................................................1
1.1. Purpose and goals............................................................................................2
1.2. Thesis overview...............................................................................................3
1.3. Description of study area..................................................................................4
1.4. References.......................................................................................................9
Chapter 2. Parameters of aquatic environmental pollution......................................10
2.1. Physico-chemical parameters, major ions and nutrients in aquatic environment..10
2.1.1. Temperature, dissolved oxygen, chemical and biological oxygen demand....10
2.1.1.1. Temperature..........................................................................................10
2.1.1.2. Dissolved oxygen (DO).........................................................................10
2.1.1.3. Chemical oxygen demand (COD)..........................................................11
2.1.1.4. Biological oxygen demand (BOD).........................................................11
2.1.2. pH................................................................................................................12
2.1.3. Electrical conductivity and total dissolved solids..........................................12
2.1.3.1. Electrical conductivity...........................................................................12
2.1.3.2. Total dissolved solids (TDS).................................................................13
2.1.4. Calcium and Magnesium..............................................................................13
2.1.4.1. Calcium.................................................................................................13
2.1.4.2. Magnesium...........................................................................................14
2.1.4.3. Hardness...............................................................................................14
2.1.5. Anions and ammonia ...................................................................................14
2.1.5.1. Bicarbonate...........................................................................................14
2.1.5.2. Sulphate................................................................................................15
2.1.5.3. Chloride................................................................................................15
2.1.5.4. Phosphate..............................................................................................16
2.1.5.5. Nitrate...................................................................................................16
2.1.5.6. Nitrite....................................................................................................17
2.1.5.7. Ammonia..............................................................................................17
2.2. Trace elements in the environment......................................................................19
2.2.1. Sources of pollution.....................................................................................19
2.2.1.1. Natural sources......................................................................................19
2.2.1.2. Anthropogenic sources..........................................................................21
2.2.2. Use..............................................................................................................21
2.2.3. Routes of trace elements in the environment ................................................23
2.2.3.1. Solubilisation........................................................................................23
2.2.3.2. Deposition in sediments ........................................................................24
2.2.3.3. Uptake by organisms.............................................................................24
2.2.4. Metals as essential and non-essential trace elements.....................................25
2.2.5. Interaction between different elements.........................................................26
2.2.6. Toxicology in humans and in aquatic ecosystems.........................................27
2.2.6.1. Toxicity in humans................................................................................27
2.2.6.2. Toxicology in aquatic ecosystem...........................................................29
2.3. Speciation of chromium......................................................................................30
2.3.1. Natural occurrence of chromium..................................................................32
2.3.2. Production, use and anthropogenic sources ..................................................32
2.3.2.1. Production.............................................................................................32
2.3.2.2. Use........................................................................................................33
2.3.2.3. Anthropogenic sources..........................................................................33
2.3.3. The redox chemistry of chromium................................................................34
2.3.4. Essentiality and toxicity...............................................................................34
2.3.4.1. Essentiality............................................................................................34
2.3.4.2. Toxicity.................................................................................................35
2.3.5. Separation of chromium species...................................................................39
2.4. References..........................................................................................................41
Chapter 3. Analytical techniques................................................................................49
3.1. Inductively Coupled Plasma Mass Spectrometry (ICP-MS)................................49
3.1.1. Principles of quadrupole ICP-MS.................................................................49
3.1.2. Liquid sample introduction in ICP-MS.........................................................50
3.1.3. The ICP as an ion source..............................................................................51
3.1.4. Quadrupole mass analyzer............................................................................53
3.1.5. Ion detection................................................................................................56
3.1.6. Interferences................................................................................................56
3.1.6.1. Spectroscopic interferences...................................................................57
3.1.6.2. Non-spectroscopic (matrix) interferences ..............................................58
3.1.7. Methods to overcome matrix effects.............................................................59
3.1.7.1. Dilution.................................................................................................59
3.1.7.2. Use of internal standards.......................................................................59
3.1.7.3. Standard addition..................................................................................60
3.1.7.4. Chemical separation..............................................................................60
3.1.7.5. Isotope dilution (ID)..............................................................................60
3.1.7.6. Matrix matching....................................................................................60
3.1.8. Analytical figures of merit for ICP-MS........................................................61
3.1.9. Environmental application of ICP-MS..........................................................62
3.1.10. Detection limits..........................................................................................62
3.2. Graphite Furnace Atomic Absorption Spectrometry (GFAAS)............................63
3.2.1. Principle and application..............................................................................64
3.2.2. Instrumentation............................................................................................65
3.2.3. Graphite Furnace multi-step temperature program........................................67
3.2.4. Background correction for absorption system...............................................68
3.2.5. Interferences and the graphite furnace..........................................................68
3.2.5.1. Physical interferences............................................................................69
3.2.5.2. Background absorption..........................................................................69
3.2.5.3. Memory effect.......................................................................................69
3.2.5.4. Chemical interferences..........................................................................69
3.2.5.4.1. Losses of analyte as a volatile salt...................................................69
3.2.5.4.2. Anion and cation interferences........................................................70
3.2.5.4.3. Carbide formation...........................................................................70
3.2.5.4.4. Condensation..................................................................................70
3.2.5.4.5. Refractory oxides ...........................................................................71
3.2.6. Methods of overcoming interferences...........................................................71
3.2.7. Advantages and limitations of GFAAS.........................................................71
3.3. References..........................................................................................................73
Chapter 4. Determination of physico-chemical parameters, major ions and nutrients
in Tinishu Akaki River, Ethiopia................................................................................77
4.1. Introduction........................................................................................................77
4.2. Study area...........................................................................................................78
4.2.1. Geography...................................................................................................78
4.2.2. Climate........................................................................................................79
4.3 Experimental.......................................................................................................79
4.3.1. Instrumentation............................................................................................79
4.3.2. Reagents:.....................................................................................................80
4.3.3. Sampling......................................................................................................80
4.3.4. Procedures...................................................................................................81
4.3.4.1. Physico-chemical parameters ................................................................81
4.3.4.1.1. Field measurements........................................................................81
4.3.4.1.2. In the laboratory.............................................................................81
4.3.4.1.2.1. COD........................................................................................81
4.3.4.1.2.2. BOD........................................................................................82
4.3.4.1.2.3. Major ions and nutrients ..........................................................83
4.4. Results and Discussion.......................................................................................83
4.4.1. Physico-chemical parameters:......................................................................83
4.4.1.1. Temperature..........................................................................................83
4.4.1.2. pH.........................................................................................................84
4.4.1.3. Electrical Conductivity..........................................................................84
4.4.1.4. Total dissolved solids (TDS).................................................................84
4.4.1.5. Dissolved oxygen (DO).........................................................................85
4.4.1.6. Chemical and Biological Oxygen Demand (COD and BOD).................88
4.4.2. Major ions and nutrients...............................................................................89
4.4.2.1. Calcium, Magnesium, hardness and bicarbonate....................................89
4.4.2.2. Nitrate, nitrite, ammonia and phosphate.................................................91
4.4.2.3. Chloride and Sulphate...........................................................................94
4.5. Conclusion..........................................................................................................95
4.6. References:.........................................................................................................96
Chapter 5. Simultaneous determination of trace elements in Tinishu Akaki River
water sample, Ethiopia, by ICP-MS...........................................................................98
5.1. Introduction........................................................................................................98
5.2. Study area...........................................................................................................99
5.2.1. Geography...................................................................................................99
5.2.2. Climate......................................................................................................100
5.3. Experimental....................................................................................................100
5.3.1. Instrumentation..........................................................................................100
5.3.1.1. ICP-MS...............................................................................................100
5.3.1.2. Microwave digestion system...............................................................101
5.3.2. Reagents and standard solution..................................................................101
5.3.3. Certified reference material........................................................................101
5.3.4. Sampling and pretreatment of samples.......................................................102
5.3.5. Physicochemical parameters, major ions and nutrients...............................102
5.3.6. Analytical procedure for trace element analysis by ICP-MS.......................103
5.3.7. Calibration.................................................................................................103
5.3.8. Microwave digestion..................................................................................103
5.4. Results and Discussion.....................................................................................104
5.4.1. Optimization of analytical procedure: internal standard and calibration method
............................................................................................................................104
5.4.1.1. Choice of Internal Standard.................................................................104
5.4.1.2. Calibration methods............................................................................105
5.4.2. Validation..................................................................................................105
5.4.3. Detection Limits ........................................................................................109
5.4.4. Analysis of Tinishu Akaki River (TAR) water samples..............................109
5.5. Conclusion........................................................................................................115
5.6. References........................................................................................................116
Chapter 6. Multi-element analysis of Tinishu Akaki River sediment, Ethiopia, by
ICP-MS after microwave assisted digestion.............................................................119
6.1. Introduction......................................................................................................119
6.2. Study area.........................................................................................................121
6.2.1. Geography.................................................................................................121
6.2.2. Climate......................................................................................................122
6.3. Experimental....................................................................................................122
6.3.1. Instrumentation..........................................................................................122
6.3.1.1. ICP-MS...............................................................................................122
6.3.1.2. Microwave digestion system...............................................................123
6.3.2. Reagents and standard solution..................................................................123
6.3.3. Sampling and pre-treatment of samples......................................................124
6.3.3.1. Sample digestion procedure.................................................................125
6.3.3.2. Analytical procedure for trace element analysis by ICP-MS................125
6.4. Results and Discussion.....................................................................................127
6.4.1. Analytical performance of digestion methods for certified reference materials
............................................................................................................................127
6.4.1.1. Precision.............................................................................................128
6.4.1.2. Accuracy.............................................................................................129
6.4.2. Detection Limits ........................................................................................132
6.4.3. Analysis of Tinishu Akaki River (TAR) sediment samples.........................132
6.5. Conclusion........................................................................................................137
6.6. References........................................................................................................139
Chapter 7. Method development for speciation of chromium in river and industrial
waste water using GFAAS........................................................................................143
7.1. Introduction......................................................................................................143
7.2. Area description and Sampling sites..................................................................145
7.3. Experimental....................................................................................................145
7.3.1. Instrumentation..........................................................................................145
7.3.2. Reagents....................................................................................................146
7.3.3. Samples, sampling and sample pretreatment...............................................147
7.3.4. Analytical Procedures................................................................................148
7.3.4.1. Cleaning of LAES...............................................................................148
7.3.4.2. Reconstitution of CRM 544 (lyophilized water sample).......................148
7.3.4.3. Separation...........................................................................................148
7.3.4.4. Calibration..........................................................................................149
7.3.4.5. UV-VIS spectrophotometry calibration curve and measurement..........149
7.3.4.6. Determination of Cr(III), Cr(VI) and Cr(tot) with GFAAS..................150
7.3.4.7. ICP-MS measurement.........................................................................150
7.4. Results and Discussion.....................................................................................151
7.4.1. Optimization of ashing and atomization temperature, GFAAS...................151
7.4.2. Validation..................................................................................................152
7.4.3. Limits of detection (LOD)..........................................................................154
7.4.4. Determination of Cr(III) and Cr(VI) in real-life samples ............................155
7.5. Conclusion........................................................................................................157
7.6. References........................................................................................................158
Chapter 8. Determination of trace elements in agricultural soil samples by ICP-MS:
microwave acid digestion versus aqua regia extraction...........................................161
8.1. Introduction......................................................................................................161
8.2. Study area.........................................................................................................163
8.2.1. Geography.................................................................................................163
8.2.2. Climate......................................................................................................164
8.3. Experimental....................................................................................................166
8.3.1. Instrumentation..........................................................................................166
8.3.1.1. ICP-MS...............................................................................................166
8.3.1.2. Microwave digestion system...............................................................166
8.3.2. Reagents and standard solution..................................................................167
8.3.3. Sampling and pre-treatment of samples......................................................167
8.3.4. Microwave acid digestion procedure..........................................................168
8.3.5. Aqua regia extraction procedure.................................................................168
8.3.6. Analytical procedure for trace element analysis by ICP-MS.......................169
8.4. Results and Discussion.....................................................................................170
8.4.1. Validation..................................................................................................170
8.4.2. Detection Limits ........................................................................................175
8.4.3. Analysis of real-life sample........................................................................175
8.5. Conclusion........................................................................................................177
8.6. References........................................................................................................178
Chapter 9. General discussion, conclusion and suggestions for future work..........181
9.1. General discussion............................................................................................181
9.2. Conclusion........................................................................................................186
9.3. Recommendation..............................................................................................187
9.4. Future work......................................................................................................187
Summary ...................................................................................................................189
Samenvatting.............................................................................................................192
Appendix A: Trends of physico-chemical parameters, major ions and nutrients..195
Appendix B: Trends of trace elements in TAR water and sediment.......................203
List of abbrevations

ACGIH American Conference of Governmental Industrial Hyienists
BCR Community Bureau of Reference
BOD Biological oxygen demand
CCME Canadian Council of Ministers for Environment
CEM Channel Electron Multiplier
C. I. Confidence Interval
COD Chemical oxygen demand
CRM Certified Reference Material
DF Dilution Factor
DL Detection Limit
DNA Deoxyribonucleic Acid
DO Dissolved oxygen
EC European Community
EPA Environmental Protection Agency
ETAAS Electrothermal Atomic Absorption Spectrometry
FAAS Flame Atomic Absorption Spectrometry
GFAAS Graphite Furnace Atomic Absorption Spectrometry
GL Guidelines
GTF Glucose Tolerance Factor
ICMR Indian Council of Medical Research
ICP-AES Inductively Coupled Plasma Atomic Emission Spectrometry
ICP-MS Inductively Coupled Plasma Mass Spectrometry
ICP-OES Inductively Coupled Plasma Optical Emission Spectrometry
ID Isotope Dilution
IRMM Institute for Reference Materials and Measurements
ISO International Organization for Standardization
IUPAC International Union of Pure and Applied Chemistry
LAES Liquid Amberlite Anion Exchange Solution