Heavy Metal Distribution in Sediment of Akpabuyo Stream, Cross River Basin Southeastern Nigeria

CHAPTER ONE

1.1 INTRODUCTION

Heavy metals pollution of aquatic ecosystem is becoming a potential global problem, pollution typically refers to chemicals or other substance in concentration greater than it would occur under natural conditions. Water pollution is the introduction by man of substances into the aquatic environment resulting from deleterious effect as harm to human health (FAO 1990).The presence of increased level of heavy metals in the aquatic environment has been of much concern for the past decades due to adverse effect of some metals on living organisms in food chains leading to man. Pollutants are the cause of major water quality degradation around the world. Several toxic metals which are important to the environment and human health have been detected in aquatic media. These toxic metals include the non-essential meals and are no importance to humans (Borgman and Norwood 2002).

Trace amount of heavy metals are always present in fresh water from terrigenous sources such as weathering of rocks resulting into geo-chemical recycling of heavy metal elements in these ecosystem. Trace elements may be immobilised within the stream sediments and could be involved in absorption, co-precipitation and complex formation. Sometimes they are co-adsorbed with other elements as oxides, hydroxides of Fe, Mn, or may occur in particulate form.

Heavy metal may enter into aquatic ecosystem from anthropogenic sources, such as industrial wastewater discharge, sewage wastewater, fossil fuel combustion, and atmospheric deposition. Trace element in stream sediment compartment can be used to reveal the history and intensity of local and regional pollution. In this work, the of stream sediment contamination was assess using geo-accumulation index.

1.2 AIMS AND OBJECTIVES

The main objectives of the current study area are:

To assess the extent and degree of metals, and the origin of these metals, using the geo-accumulation index of the metals.

To determine the total content of heavy metals in surface sediments of Akpabuyo.

To estimate the anthropogenic input and to assess the pollution status on the area.

1.3 STUDY AREA

The study area which is located in Akpabuyo, Cross River State lies between longitudes 80 22I 30II E – 80 30I 0II E and latitude 40 52I 30II N – 40 57I 30II N (fig 2). With an area of 126,4032 Square Km. Although many stream samples where collected but few was selscted for the heavy metal analysis. The various Locations in Akpabuyo which sediment samples were collected and used to carry out the analysis are Esuk Mbat stream(L1), Esuk Ekpo Eyo Stream(L2), Ikot Akwa Stream(L3), Dan Archibong Stream(L4), Itu Stream(L5), Ikot Ndarake Stream(L6), Asioha Stream(L7), Ikot Ekpo Ene Stream(L8), Ekpene Ikot Imo Stream(L9), Ikot Nakanda(L10), and their following coordinate shown respectively (table 1.3) . It originate from a hilly region and flows through several villages and farmland.