CHAPTER ONE
1.1 Introduction
Heavy metals are those metallic elements with high atomic or specific gravity that is at least five times greater than that of water. Several elements have been listed in this group. The presence of heavy metals in the aquatic environment in trace concentrations is important for normal development of the organism (Kori-Siakpere and Ubogu, 2008).
They could be detected in the aqueous medium and in the bottom; some however, are completely deleterious and need to be monitored continuously in the bodies of organisms as they are capable of bioaccumulation, resulting to morbidity and often mortality of organisms (Ayotunde et. al, 2011, 2012., and Ada, et. al., 2012). Heavy metal human health concern has stimulated a lot of research in this area, some of which include the works of Muchuweti
et. al., (2006), Satarug et. al. (2000) and Adefemi et. al. (2012).
When metals enter aquatic environment, a great portion settles and is absorbed by the bottom mud (Ayotunde, 2012). They could be recycled by chemical, physical and biological processes such that some quantity remains dissolved in the water column and some part is being absorbed by the inhabitants (Rayms- Keller et. al., 1998 and Kori- Siakpere and Ubogu, 2008). Fishes are at the apex of the food chain and can bio accumulate some of these substances into their tissues (Olaifa et. al., 2004).