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«AN ASSESSMENT OF HEAVY METAL CONTAMINATION OF SEDIMENTS AND TISSUES OF THE CLAM GALATEA PARADOXA (BORN 1778) IN THE VOLTA ESTUARY, GHANA A THESIS ...»

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AN ASSESSMENT OF HEAVY METAL CONTAMINATION OF

SEDIMENTS AND TISSUES OF THE CLAM GALATEA PARADOXA

(BORN 1778) IN THE VOLTA ESTUARY, GHANA

A THESIS SUBMITTED TO THE DEPARTMENT OF FISHERIES AND

WATERSHED MANAGEMENT IN PARTIAL FULFILMENT OF THE

REQUIREMENTS FOR THE AWARD OF THE DEGREE OF

MASTER OF PHILOSOPHY (MPHIL) IN

FISHERIES SCIENCE AND WATERSHED MANAGEMENT

BY

OBIRIKORANG KWASI ADU

(BSc. HONS)

KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY

FACULTY OF RENEWABLE NATURAL RESOURCES

KUMASI MAY, 2010 i

KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY

FACULTY OF RENEWABLE NATURAL RESOURCES

DEPARTMENT OF FISHERIES AND WATERSHED MANAGEMENT

KUMASI, GHANA

AN ASSESSMENT OF HEAVY METAL CONTAMINATION OF

SEDIMENTS AND TISSUES OF THE CLAM GALATEA PARADOXA

(BORN 1778) IN THE VOLTA ESTUARY, GHANA

A THESIS SUBMITTED TO THE DEPARTMENT OF FISHERIES AND

WATERSHED MANAGEMENT IN PARTIAL FULFILMENT OF THE

REQUIREMENTS FOR THE AWARD OF THE DEGREE OF MASTER OF

PHILOSOPHY (MPHIL) IN

FISHERIES SCIENCE AND WATERSHED MANAGEMENT

BY

OBIRIKORANG KWASI ADU

(BSc. HONS)

SUPERVISED BY:

DR. S. AMISAH

DEPARTMENT OF FISHERIES AND WATERSHED MANAGEMENT,

KNUST, KUMASI, GHANA PROF. H.A. MADKOUR

NATIONAL INSTITUTE OF OCEANOGRAPHY AND FISHERIES,

RED SEA BRANCH, HURGHADA – EGYPT

DR. F.A OTCHERE

ENVIRONMENTAL/TOXICOLOGICAL CONSULTANT

BINPAL ENGINEERING LTD.

SURREY, BC. CANADA MAY, 2010 ii

STATEMENT OF ORIGINALITY

“I hereby declare that this submission is my own work and that, to the best of my knowledge and belief, it contains no material previously published or written by another person nor material which to a substantial extent has been accepted for the qualification of any other degree or diploma of a university or other institution of higher learning, except where due acknowledgement is made” ………………………….. ……………………………..

Kwasi Adu Obirikorang Date (Student) Certified by …………………………… …………………………….

Dr. Steve Amisah Date (Internal Supervisor) Certified by ……………………………. ……………………………..

Dr. Steve Amisah Date (Head of Department)

–  –  –

__________________________________________________

Dear Prof. Dr. | Head of Department of Fisheries and Watershed Management, Faculty of Renewable Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana I am delighted to confirm that I have seen and read the thesis entitled

" AN ASSESSMENT OF HEAVY METAL CONTAMINATION OF SEDIMENTS

AND TISSUES OF THE CLAM GALATEA PARADOXA (BORN, 1778) IN THE VOLTA ESTUARY, GHANA" produced by Mr.\ OBIRIKORANG KWASI ADU from Department of Fisheries and Watershed Management, Faculty of Renewable Natural Resources, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.

I can confirm that the thesis is a substantial and scholarly piece of work, that is has been the result of a large amount of practical study and data analysis and that is has been written scientifically after consulting the available literature.

I can further confirm that I am willing and happy for the thesis to be submitted to the examiners (External Examination).

–  –  –

µg/g dw: Microgram per gram dry weight µg/g: Microgram per gram µg/ml: Microgram per millilitre AAS: Atomic Absorption Spectrophotometer AF: Accumulation Factors Al: Aluminium ANOVA: Analysis of variance ANZECC: Australian and New Zealand Environment and Conservation Council As: Arsenic AVFs: Acid-Volatile sulfides BCF: Biological Concentration Factors BSAF: Biosediment Accumulation Factors Cd: Cadmium CIFA: Committee for Inland Fisheries of Africa Co: Cobalt Cr: Chromium Cu: Copper DO: Dissolved Oxygen DWAF: Department of Water Affairs and Forestry EAF: East Africa Marine Pollution and Research Praogramme FAO: Food and Agriculture Organisation Fe: Iron g: gram g/cm³: gram per centimetre cubed GESAMP: The Group of Experts on Scientific Aspects of Marine Environmental Protection H2SO4 : Sulphuric Acid HCl: Hydrochloric Acid HClO4: Perchloric Acid Hg: Mercury HNO3: Nitric Acid IAEA: International Atomic Energy Agency IOC: Intergovernmental Oceanic Commission IQ: Intelligence Quotient KMnO4: Potassium Permanganate LDPE: Low-density polyethylene m2 /day: Meter squared per day MEDPOL: Mediterranean Pollution Monitoring and Research Programme ml: Millilitre Mg/kg: Milligram per kilogram mg/km: Milligram per kilometer mg/kg: Milligram per kilogram Mg: Magnesium Mn: Manganese Mo: Molybdenum NAS/NRC: National Academy of Science of the National Research Council Nb: Niobium v ND: None Detected ng/g: Nanogram per gram Ni: Nickel ºC: Degrees Celsius Pb: Lead ppm: Part per million PTEs: Potential Toxic Elements Rb: Rubidium RNA: Ribonucleic acid Sb: Antimony Se: Selenium SnCl2·2H2O: Stannous Chloride SPM: Suspended Particulate Matter Sr: Strontium TDS: Total Dissolved Solid UNECE: United Nations Economic Commission for Europe UNEP: United Nations Environment Programme UNESCO USEPA: United States Environmental Protection Agency V: Vanadium VRA: Volta River Authority WACAF: West and Central Africa Marine Pollution and Research Programme WHO: World Health Organisation Y: Yttrium Zn: Zinc Zr: Zirconium





vi ABSTRACT

The concentrations of four heavy metals, Mn, Zn, Fe (essential heavy metals) and Hg (non-essential heavy metal) were determined in sediments and in whole soft tissue of the clam Galatea paradoxa (Born 1778) from two clam fishing locations, Ada and Aveglo at the Volta Estuary in Ghana over an 18-month period. Thirty (30) clams were obtained from each sampling location monthly and grouped into three size classes of 10 individuals each based on shell lengths as follows: small (25 mm), medium (41-55mm), and large (above 55mm). The groupings were chosen based on the three dominant size groups in the natural population to give a broad and representative range of metal concentrations in the clams. All the results were expressed as total concentrations (µg/g dry weight (dw). Mean concentrations of analyzed metals in the tissue of the clams from the Ada sampling station were: Mn: 152.9 µg/g; Fe: 174.9 µg/g, Zn: 34.6 µg/g and Hg: 0.043 µg/g. The mean metal concentrations in the Aveglo clams were: Mn: 130.0 µg/g, Fe: 187.0 µg/g, Zn: 37.1 µg/g and Hg: 0.046 µg/g. Mean metal concentrations in the sediments were Mn: 186.0 µg/g, Fe: 1770.4 µg/g, Zn: 3.2 µg/g and Hg: 0.0086 µg/g for the Ada sampling station. The Aveglo sediments had

mean metal concentrations as follows: Mn: 171.9 µg/g, Fe: 1758.5 µg/g, Zn: 3.7 µg/g and Hg:

0.0115 µg/g.

Metal concentrations in the tissues of the different clam size-classes (small vs. small, medium vs.

medium and large vs. large) from the two sampling stations were almost identical and did not vary significantly (p0.05). A comparative evaluation of the metal concentrations in the clams and sediments from the two stations, however revealed significant variations in concentrations for Zn Fe and, Hg. Concentration of Fe in the Ada sediment samples for June was as much as 18 times higher than the concentration in the clams and Hg concentrations were approximately five (5) times higher in the clam tissues than in the sediments during the study period. On the basis of calculated BSAFs the metal enrichment in the tissues of the clams rank in the following order ZnHgMnFe. The BSAFs indicated a significant accumulation of Zn and Hg in the clam tissues relative to the concentrations of these metals in the sediments although no clear relationships were established between the concentrations of the studied heavy metals in the clam tissues and sediments.

There were no significant differences (p 0.05) in Mn, Fe and Zn concentrations among the different size classes except for Hg concentration in clams from Ada, indicating a similar bioavailability of Mn, Fe, Zn at both locations and, possibly, an efficient metabolism to keep the concentrations of Mn, Fe and Zn relatively similar in the tissues of the different clam sizes. Spatial variations in metal concentrations in the clams (i.e., Ada small vs. Aveglo small, Ada medium vs.

Aveglo medium, and Ada large vs. Aveglo large) were not significant for all four studied metals in the compared size classes. Results of the statistical test for spatial variations in the sediment samples from the two stations also revealed no significant differences (p0.05) in the concentrations of Mn, Zn, Fe and THg during the study period.

To understand the relationships between metal concentration in the sediments and accumulation in the tissues of the three clam size classes as far as Mn, Zn, Fe and Hg were concerned, the monthly concentrations of the studied metals were graphed to observe distinct metal accumulation patterns The graphs revealed no simple linear relationships between the concentrations of heavy metals in the clam tissues and the sediments at the two sampling stations although some distinct accumulation trends were observed as far as Mn was concerned.

vii Analysis of risks levels associated with the consumption of clams by humans revealed that the concentration of the Mn, Zn, Fe and Hg found in the clam tissues were within permissible limits using reference guides such as the WHO Safety Reference Standards for Bivalves and various indicators as the Tolerable daily Intake (TDI), rate of shellfish consumption (RSC), Risk Quotients (RQs) and levels of concerns (LOCs) Based on geoaccumulation calculations, the sediments from the two sampling stations are unpolluted as far as the heavy metals, Manganese, Zinc, Iron and Mercury are concerned and the samples are similar to those observed in areas under low pollution impact.

–  –  –

I would like to express my appreciation for the assistance and advice I have received from my supervisors Dr. Steve Amisah, Prof Hashem Abass Madkour and Dr. Fred Ato Otchere. I am incredibly grateful for their help and consistent confidence in me and their constructive criticisms during the past two years.

I also appreciate the immense contribution of Mr. Daniel Adjei-Boateng towards the field sampling and laboratory work and also providing me with the relevant literature and baseline data for this thesis.

My gratitude also goes to Nana Akwasi Osei, Bernard Owusu-Appiah and Michael Kojo Essel for their assistance on the field and in the laboratory during the project period.

I would also like to thank Mr. David Azanu of the Department of Chemistry of KNUST for his assistance in Mercury analysis and for spending his precious time helping me run my samples. I also appreciate his efforts in helping me with instrumental difficulties and for providing analytical advice.

Last, but not least, I express my heartfelt appreciation to my family for their financial support and their encouragement.

–  –  –

1.1 Background Heavy metals may occur in aquatic environments from natural processes and from discharges or leachates from several anthropogenic activities (Connell et al., 1999; Franca et al., 2005). The contamination of natural waters by heavy metals negatively affects aquatic biota and poses considerable environmental risks and concerns (Cajaraville et al., 2000; Ravera, 2001). Monitoring programmes and research on heavy metals in aquatic environments samples have become widely important due to concerns over accumulation and toxic effects in aquatic organisms and to humans through the food chain (Otchere, 2003). Contaminants can persist for many years in sediments in both freshwater and marine systems where they hold the potential to affect human health and the environment (Mackevičiene et al., 2002).

Sediments are an important sink of a variety of pollutants, particularly heavy metals and may serve as an enriched source for benthic organisms (Wang et al., 2002) especially in estuarine ecosystems.

Metals may be present in the estuarine system as dissolved species, as free ions or forming organic complexes with humic and fulvic acids. Additionally, many metals e.g. Pb associate readily with particulates and become adsorbed or co-precipitated with carbonates, oxyhydroxides, sulphides and clay minerals. Consequently, sediments accumulate contaminants and may act as long-term stores for metals in the environment (Spencer and MacLeod, 2002). Exposure of sediment-dwelling organisms to metals may then occur via uptake of interstitial waters, ingestion of sediment particles and via the food chain (Luoma, 1989). The occurrence of elevated concentrations of trace metals in sediments found at the bottom of the water column can be a good indicator of man-induced pollution rather than natural enrichment of the sediment by geological weathering (Davies et al.

1991, Chang et al. 1998).

The analyses of water or sediment samples, however, are subject to a variety of shortcomings, in that the methods do not allow for the estimation of the quantity of the metal which is biologically available (Etim et al., 1991). It is against this background that bio-indicators are preferred in environmental monitoring. Bivalves are effective biomonitors and have been widely used for heavy metal monitoring purposes worldwide (Phillips and Yim, 1981, Etim et al., 1991, Ferreira et al., 2004, Otchere, 2003, Tay et. al., 2004).



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