CHAPTER ONE

INTRODUCTION

Trace metals are chemical elements found in all kinds of soils and arePredominant in soils with density greater than 5g/dm3 (Freedman, 1996). The very low general level of their content in soils and plants as well as the biological role of most of them makes them microelements. (Lacatusu, 1998). Assessment of trace metal levels in soils around various industries have been a major concern over the years, due to increased industrial activities as well as poor waste management. The levels of lead, copper, cadmium, nickel, and so on have been chosen as representative metals for which their concentration in the environment may be used as a reliable index of environmental pollution.

              Among the various toxic substances released through industrial activities, trace metals have been seen as a key marker because they can be analysed effectively and consistently in most environmental matrices. These inorganic pollutants are not degradable by natural processes unlike their organic counterpart, which degrade to less harmful components as a result of biological or chemical processes. Hence the efforts of trace metal pollution on local environments in close proximity to these industrial areas may therefore be substantial and long lasting inspite of extensive remediation efforts. (Amiard, Meyer 1995).

In addition, increased automobile repair activities in Nigeria as a result of excessive inflow of used tokunbo vehicles into the country has contribute significantly to the problem of soil contamination in most cities. The waste oil used for cleaning machine parts during servicing, the grease used for lubrication, metal scraps as well as used batteries are indiscriminately discarded on soils by automobile Engineers. The metals from these sources gets into the soil matrix and are taken up by plants in amounts that has detrimental effects on people or animals that consumes these plants. The problem of trace metal pollution is not restricted to Nigeria alone, in most parts of the world, large amount of trace metal have been directly discharged to nearby lands as well as surface water where food crops are grown and animals are reared, and human beings feed on these things. This activity adversely affects the quality of air, soil and ground water, in such a way that it becomes a subject of serious concern worldwide.