Abstract
Ten representative soil samples were collected along major gutters within Nkpor
metropolis. The soil samples were digested using mixtures of HF and aqua regia
in ratio1:1. The heavy metals contents of the digested soil samples were
determined via Flame Atomic Absorption Spectrophotometer FAAS. Sample A
had the highest concentration of heavy metal and the trend was Ni > Cr > Hg >
Zn > As ~ Cd, it was followed by sample B with Ni > Cr > Zn > Zn > Cd >g >
As, sample C had Ni>Cr >Zn>Hg>Cd>As, sample E had Ni > Zn > Cd > Cr >
Hg > As. While sample D had Cr > Ni > Zn > Cd > Hg > As. Also the results of
the sequential extraction of each soil sample indicated that Ni had the highest
percentage bioavailability (49.61%), Hg (47. 72%), Cr (42. 19%), Zn (39.66%),
Cd (35.10%), As (0.00%). The high concentration of Hg, Cr and Cd in most areas
of the metropolis indicated gross contamination, which could have resulted from
human activities, hence the need to adequately monitor the release
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).
Therefore, with greater public awareness of the implications of contaminated soils on
humans and animal health, there has been increasing interest among scientific
communities in the development of technologies to determine the total concentrations
of these elements of interest in the soil as well as their chemical forms.
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The use of sequential extraction techniques to fractionate metals in soils and evaluate
their potential effects has become very useful and well recognized (4)
1.1 SCOPE OF STUDY
This research covers the analysis of six heavy metals in each of the five selected
drainage pathways or gutters in Nkpor. The heavy metals are mercury (Hg)
Nickel; (Ni), Zinc (Zn), Arsenic (As), Cadmium (Cd), Mercury (Hg)
Soil samples were collected from each of the drainage systems as follows:
Five soil samples each along Nkpor/Enugu Old Road, Nkpor/Obosi Road (site for
Geolis Cables Industry), Limca Road Nkpor, New Market Road Nkpor and
Nkpor/Enugu Express Road.
The samples will be collected at a distance of 10 meters each to avoid bias. A total of
25 soil samples will be analysed to determine the total concentration of each metal in
each sample.
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1.2 AIMS AND OBJECTIVES OF STUDY
Heavy metal content of soil sample in some selected drainage systems in Nkpor
will be investigated. As earlier on stated, heavy metals are dangerous because
they tend to bioaccumulate i.e increase in their concentration over time. Also
heavy metals can enter water supply by industrial and consumer waste or even
from acidic rain and release heavy metal into streams, lakes, rivers and ground
water.
Hence, the study will help in assessing the potential environmental impacts of
these metals by determination of their concentrations in soils as well as the
chemical form of these metals in the soil.
OBJECTIVES OF THIS STUDY
The objectives of this study are:
(a) To determine the total concentration of some selected heavy metals in gutter.
(b) To use sequential extraction technique to fractionate metals in soil samples