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(Algae and Chironomids) from Kenyan Saline Lakes (Bogoria and Nakuru): Evaluation and Verification of Two Compartment Toxicokinetic Models

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(Algae and Chironomids) from Kenyan Saline Lakes (Bogoria and Nakuru): Evaluation and Verification of Two Compartment Toxicokinetic Models BIOACCUMULATION OF TRACE METALS IN BIOTA (ALGAE AND CHIRONOMIDS) FROM KENYAN SALINE LAKES (BOGORIA AND NAKURU): EVALUATION AND VERIFICATION OF TWO COMPARTMENT TOXICOKINETIC MODELS. Von der Fakultät für Mathematik und Naturwissenschaften der Carl von Ossietzky Universität Oldenburg zur Erlangung des Grades und Titels eines Doktors der Naturwissenschaften (Dr. rer. nat.) angenommene Dissertation Von Frau Muohi, Ann Wairimu Geboren am 20th 10 1975 in Thika. ii Gutachterin/Gutachter: Dr. Gerd-Peter Zauke Zweitgutachterin/-gutachter: Prof. Dr. Hans-J Brumsack Tag der Disputation: 11/12/2007 iii BIOACCUMULATION OF TRACE METALS IN BIOTA (ALGAE AND CHIRONOMIDS) FROM KENYAN SALINE LAKES (BOGORIA AND NAKURU): EVALUATION AND VERIFICATION OF TWO COMPARTMENT TOXICOKINETIC MODELS. By ANN WAIRIMU MUOHI B.Ed. hons. Kenyatta University, Kenya. M.Sc. University of Nairobi, Kenya. Supervisors First: Dr. Gerd-Peter Zauke…………………………………… Second: Prof. Dr. Hans-J. Brumsack….....……………….……… Local: Prof. Kenneth M. Mavuti …….………………………… A THESIS SUBMITTED TO THE FACULTY OF MATHEMATICS AND NATURAL SCIENCES, AT THE CARL VON OSSIETZKY UNIVERSITÄT, OLDENBURG, GERMANY, IN FULFILMENT OF THE DEGREE OF DOCTOR OF rer.nat. (NATURAL SCIENCES) ii Acknowledgments This study was first developed with the initiative and under the supervision of the late Prof. Dr. Ekkehard Vareschi. Much tribute is thus paid, in his memory and that of his wife Angelika, who together encountered an accident during a scientific field trip in Momella National Park, Arusha, Tanzania. I am very grateful to The Deutscher Akademischer Austausch Dienst (DAAD) for the full sponsorship of this study. I express my gratitude to The Carl von Ossietzky Universität, Oldenburg (UoO), for granting me the academic registration towards the fulfilment of this study. I am also highly grateful to the University of Nairobi (UoN), for granting me study leave to enable me pursue this study. I am exceptionally thankful to all my supervisors, Dr. Gerd-Peter Zauke and Prof. Dr. Hans J. Brumsack of The Carl von Ossietzky Universität, Oldenburg, Germany, and, Prof. Kenneth M. Mavuti of The University of Nairobi, Kenya, for their constant academic guidance and advice, which were invaluable towards the realisation of this work. Dr. G-P Zauke did also diligently oversee all other relevant matters pertinent to my stay in Germany. Prof. K. M. Mavuti’s facilitation of an effective running of my field works in Kenya, was in deed invaluable. I am highly indebted to other members of the Aquatic Ecology working group at the UoO, particularly Kristine Jung and Edith Kieselhorst, for their patience and tireless academic and technical support, especially during the AAS analysis, among other nerve stretching occasions. I also do express much gratitude, to especially Dr. Bernhard Schnetger for his assistance with the XRF analysis and for his engagement in academic discussions. I am as well, much indebted to other members of the Microbiogeochemistry working group at the UoO, especially Ms. Carola Lehners and Ms. Martina Wagner among others, for their technical support during XRF analysis preparations. I am grateful to The School of Biological Sciences, UoN, for assistance with laboratory and relevant fieldwork facilities. I thank Messers Francis Nyaga, Daniel Kamau, Kagori Kuria and Benson Chalo among others, for their assistance with necessary laboratory logistics at the School of Biological Sciences, UoN. I also thank Dr. Joseph Githaiga, for availing me some relevant literature materials and for his engagement in academic discussions. iii I am highly grateful to The Kenya Wildlife Society (KWS), for granting me unlimited admission into the Lake Nakuru National Park and Lake Bogoria National Reserve, to enable me access the relevant study sites. KWS also provided rangers for the crucial security measures while at the park. I also thank the KWS for allowing me access to The Nakuru Municipal/Lake Nakuru Laboratory facility. I am as well indebted to Messers Andrew Kulechu, Ngatia Waweru, Gilbert Mutai, Cyrus Nyakundi, Johana Mbugua and Biwott among others, for their indispensable assistance with necessary logistics at the Lake Nakuru National Park and in the laboratory. I do also thank Messers, James Kimaru, Reuben Ndolo, Mbogo kamau and James Njoroge of the Earthwatch Team, for their assistance with vital field logistics especially at The Lake Bogoria Reserve. I appreciate all my friends at large, for their academic, logistical and moral support, at variant times during the course of this study. I am in particular highly glad for the assistance of Messers, David K. Mugo and Thomas Muiruri among others, for their logistical assistance especially during sediment samples preparations. I do also appreciate the moral support and friendship, of the entire members of The Cameroon Students Association, University of Oldenburg (CAMSAO), during my stay in Oldenburg. I am grateful to Roul Keminsi and Mark Chofor for their assistance in computer and other logistics during my thesis write-up. Lastly, but not in any way the least, I do thank especially my parents, extended family at large and well wishers, for their ever eminent moral support, affirmative prayers and favourable wishes. iv Dedication To My Family v Abstract This study was carried out to assess the suitability of various aquatic biota particularly those associated with some Kenyan Saline lakes, as biomonitors of trace metals. The study also aimed at evaluating the use of two-compartment and logistic regression models as predictive tools in assessment of environmental quality in the specific ecosystems. Experimental organisms namely, algae (Arthrospira fusiformis) and chironomids (Lepotochironomous deribae) among others, were obtained particularly from, Lakes Bogoria and Nakuru. Environmental sediment samples were also collected from the lakes, for a survey of the pertinent elemental background levels. Using the obtained organisms, exposure and depuration experiments were set up at The Nakuru Municipal/L. Nakuru National Park laboratory and at The School of Biological Sciences in the University of Nairobi, Kenya. Experimental samples were stored in a freezer at -20 °C and were later dried at 80 °C, before transportation to the Aquatic Ecology Laboratory in The University of Oldenburg, Germany, for chemical and data analysis. In the chemical analysis, aliquots of 10 mg samples were digested in 2 ml safe-lock Eppendorf reaction tubes for 3 hours at 80°C with 100 µl HNO3 (65% suprapure). Cadmium, Cu and Pb elements were analysed using a Varian SpectrAA 880 Zeeman instrument and a GTA 110 graphite tube atomiser. Zinc was analysed using an air-acetylene flame (Varian SpectrAA-30, deuterium background correction) and a manual micro-injection method (100 µl sample volume). All metal concentrations in biological tissues are reported in µg g-1 dry weight (dw). For validation of the method, Certified Reference Materials (CRMs) namely BCR-CRM No.279 Sea Lettuce (Ulva lactuca) and Standard reference Material 1572 Citrus leaves, from the Commission of The European Communities (Community Bureau of Reference), and TORT-2 Lobster hepatopancreas and CRM 278R Mussel tissue (Mytilus Edulis) from the National Research Council of Canada were analysed using the same methods. Results obtained were in agreement with the certified values at 95% confidence level. Statistical analysis and modelling were done using SYSTAT version 10 and EXCEL programmes. In the results, the bioaccumulation phenomena in the investigated organisms were basically overt. The relevant bioconcentration factors (BCFs), which were higher than zero, were a confirmation to this. The elemental uptake and elimination trends though, were organism dependent and element specific. In the time dependent exposures, elemental uptake in algae took place fast, that is within hours other than within days. In comparison to other assessed elements (Cd, Pb and Zn), Cu in algae, seemed to have a more rapid uptake rate. Nevertheless, Cd and Cu elements demonstrated more reliable models as compared to Pb and Zn, in algae. Relevant model verifications showed that, model reproducibility was element specific and probably ecosystem dependent. In the concentration dependent exposures, elemental concentrations in organisms did tend to increase with increasing exposure. Nonetheless, the elemental increment trends vi differed between elements, between replicate exposures, between the extent of exposure ranges, and even between ecosystems. Nakuru algae Cu concentration dependent uptake trends were however, exceptionally consistent. Upon verification of time dependent exposure models through prediction of concentration dependent outcomes, a higher predictability chance was demonstrated when using model parameters and data from organisms of the identical ecosystem. The elemental uptake predictability chance though, and hence the model authenticity, depended on the exposure concentrations pertinent to the predicting parameters and the predicted data. For the chironomids, just like in the case of algae, elemental uptake and elimination courses viz a vis model authenticity, were basically, element specific. In the chironomids however, reliable models were not only obtained for Cd and Cu elements, but also for Pb and Zn in some instances. Additionally, the chironomids concentration dependent elemental uptake trends, were notably more distinct and consistent, as opposed to those of algae. Besides, the most predictable concentration dependent elemental uptake trends,
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