CHAPTER ONE

INTRODUCTION

1.0 GENERAL INTRODUCTION

Minerals, metals and metalloids, toxic or essential, are present in soils or sediments in various forms with varying bioavailability, toxicities and mobilities. Heavy metals are natural components of the earth’s crust and the ecosystem with variations in concentration. They cannot be degraded or destroyed and they enter our bodies via food, drinking water and air [1].

Unlike organic contaminants, most metals do not undergo microbial or chemical degradation and the total concentration of these metals in soils persist for a long time after their introduction [2].

These metals are a cause of environmental pollution (heavy-metal pollution) from a number of sources. For example lead in petrol, industrial effluents and leaching of metal ions from the soil into lakes and   rivers by acid rain [3].

Living organisms require varying amounts of “heavy metals”. Iron, cobalt, copper, manganese, molybdenum and zinc are required by humans. Excessive levels can be damaging to the organisms. Other heavy metals such as mercury, plutonium and lead are toxic metals that have no beneficial effect on organisms and can cause serious illnesses (3).

1. 1. This material content is developed to serve as a GUIDE for students to conduct academic research work
2. 2. As a source for additional understanding of the subject.
3. 3. As a source for ideas for your own research work (if properly referenced).
4. 4. For PROPER paraphrasing (see your university definition of plagiarism and acceptable paraphrase)
5. 5. Direct citing (if referenced properly)
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