ABSTRACT

The presence and bioaccumulation pattern of some heavy metal concentrations in wild and

farmed African catfish, Clarias gariepinus (Burchell, 1822) muscles collected from selected

rivers and fish farms in Kaduna State, Nigeria, were assessed. Fish and water samples used for

the assessment were collected during the wet and dry seasons from River Kaduna, River

Galma in Zaria; and from two fish farms in Sabon Tasha, Kaduna and Dakace, Zaria. Physico-

chemical parameters, such as Puissance Hydrogen (pH), temperature, Turbidity etc., were also

analysed. The analyses of heavy metals, Iron (Fe), Lead (Pb), Nickel (Ni), Cadmium (Cd) and

Mercury (Hg), in all water and Clarias gariepinus muscle samples was carried out in the

Multi-User Science Research Laboratory, Department of Chemistry, Ahmadu Bello

University, Zaria, using Thermo-element Solar S4 Atomic Absorption Spectrophotometer

(AAS), while the Varian Generation Accessory (VGA 77) with closed end cell was used for

Hg determination. The results obtained were subjected to t-test analysis to determine the level

of significance (p < 0.05) between the means, while Pearson correlation coefficient was

employed to determine the relationships. pH was highest in River Kaduna during the wet

season, in the upstream (7.04), while there was a dip in the downstream (6.67) during the dry

season. Seasonal variations in temperature were evident, as the ranges obtained in the rivers

were from 27.03°C – 30.68°C and the farms ranged from 23.76°C – 27.42°C, which were

within World Health Organization (WHO) recommended threshold (30°C – 36°C). Dissolved

Oxygen (DO) varied widely in the rivers (5.11mg/l – 7.04mg/l) as well as in the farms

(9.29mg/l – 10.74mg/l). Total dissolved solids (TDS)obtained in this study were all very high

(Rivers 54.91mg/l – 82.09mg/l, Farms 28.43mg/l – 42.03mg/l), but were all lower than the

WHO standardindicativeofportability (1000 – 1600mg/l). Heavy metal concentrations in

water samples and heavy metal bio-accumulation in both wild and farmed C. gariepinus

muscles showed irregular distributions with descending order ofFe >Pb>Hg>Ni > Cd. Fe

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1.0       INTRODUCTION

1.1       Background of the Study

In recent years the concentrations of toxic metals in many ecosystems are reaching

unprecedented levels. The increasing use of metals in industry and mining activities have led

to serious environmental pollution through effluents and emanations (Güven et al., 1999).

Under certain environmental conditions, heavy metals may accumulate and cause serious

ecological damage. The aquatic ecosystem is often seen as the ultimate recipient of almost

everything including heavy metals (Ogoyi et al., 2011). Pollution of heavy metals in aquatic

environment is a growing problem worldwide and currently it has reached an alarming rate.

There are various sources of heavy metals; some originates from anthropogenic activities like

draining of sewage, dumping of hospital wastes and recreational activities. Conversely,

metals also occur in small amounts naturally and may enter into aquatic system through

leaching of rocks, airborne dust, forest fires and vegetation (Fernandez and Olalla, 2000). As

heavy metals cannot be degraded, they are continuously being deposited and incorporated in

water, sediment and aquatic organisms (Linnik and Zubenko, 2000), thus causing heavy

metal pollution in water bodies.

Heavy metal is any metallic chemical element that has a relatively high density and is toxic or

poisonous at low concentrations (Ngumbu, 2014). Examples of heavy metal include mercury,

cadmium, arsenic chromium, thallium and lead. As trace elements, some heavy metals (e.g.

copper, iron, zinc, manganese and selenium) are essential to maintain the metabolism of the

human body. However, at higher concentrations they can lead to poisoning (Lenntech, 2014).

Heavy metals can enter the human food through water, air, soil, plants and animals. The

pollution of the environment by heavy metals is viewed as an international problem because

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of its effects. In recent years, the pollution of aquatic environment with heavy metals has

become a worldwide problem because of their potential toxic effect and also most of them

accumulate in tissues and organs of aquatic organism (Goldstein and Hewitt,

1990andGledhill et al., 1997).