ABSTRACT
This study was carried out to investigate the effect of
illegal small-scale gold mining ("Galamsey") operations on the water
quality of the Akantansu and Sintim rivers in the Asutifi North District of the
Brong-Ahafo Region of Ghana. Water samples were collected from the two rivers
for physico-chemical and heavy metal analyses. Levels of physico-chemical
parameters were determined by standard methods while heavy metals were by
Atomic Absorption Spectrophotometry (AAS). Results show that, generally, higher
values were recorded at downstream locations for most of the phyisco-chemical
parameters studied. Mean values for temperature, pH, conductivity, TDS and TSS
were within the WHO recommended guideline values for drinking water. However,
samples from the rivers were found to be very turbid (> 5 NTU) and
consequently coloured (> 20 TCU). Dissolved oxygen decreased at the
downstream sampling locations and the mean values were generally slightly below
the 5 mg/l recommended by the WHO. Mean levels of copper, arsenic, lead,
cadmium and mercury were generally higher downstream of the rivers, but were
lower than the WHO acceptable limits. However, levels of iron were above the
WHO acceptable limits, with very high values being recorded downstream of the
rivers. The general trend in the levels of the parameters studied suggests
influence from the small-scale gold mining activities along the banks of the
two rivers.
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND OF THE STUDY
Water is one of the most essential
constituents of the human environment. The water resources generate development
in socio-economic issues crucial to the society in general and more
specifically for industries, agricultural activities and for the public use.
The Hungarian Nobel prize winner
Albert Szert-Gyargyi once said, “Water is life’s mater and matrix, mother and
medium. There is no life without water.” if the water resources are
contaminated, so is life. Providing clean drinking water for the growing
population of the world is one of the most pressing issues we stand against in
the 21st century. Both anthropogenic and natural processes can affect the water
quality. Except from the metals man has created through nuclear reactions, the
rest has been on Earth since the planet was formed. There are few examples of
local metal pollutions through natural weathering but in most cases metals
become an environmental health issue because of anthropogenic activity. Mainly,
mining and smelting plant release metals from the bedrock (Walker and Sibly,
2001).
Integrated water resources
management (IWRM) is an essential approach to water resources within the
catchment. There are different activities (such as mining) that occur within a
catchment that use and affect water resources. The impacts of mining activities
for instance, can create problems for ecosystems functioning.
Comprising of about 70% of the
surface of the Earth, water is the most valuable natural resource existing on
our planet. Without this invaluable compound, life on the earth would not exist. Although this fact is
widely recognized, pollution of water resources is a common problem being faced
today. Heavy metal pollution occurs directly by effluent outfalls from
industries, refineries and waste treatment plants and indirectly by the
contaminants that enter the water supply from soils/groundwater systems and
from the atmosphere via rain water (Vijayaraghavan and Yun, 2008). Modern
industry is, to a large degree, responsible for contamination of the
environment. Lakes, rivers and oceans are being overwhelmed with many toxic
contaminants. Among toxic substances reaching hazardous levels are heavy metals
(Vieira and Volesky, 2000). Heavy metals are the group of contaminants of
concern, which come under the inorganic division. Some metal ions such as
mercury are very toxic even in concentrations as low as 0.001 mg/l. Under
certain environmental conditions, metals may accumulate to toxic levels and cause
ecological damage (Jefferies and Firestone, 1984). Of the important metals,
mercury, lead, cadmium, arsenic and chromium (iv) are regarded as toxic,
whereas, others such as copper, nickel, cobalt and zinc are not as toxic, but
their extensive usage and increasing levels in the environment are of serious
concern (Brown and Absanullah, 1971; Moore, 1990; Volesky; 1990). Various
techniques have been employed for the treatment of metal bearing industrial
effluents, which usually include precipitation, adsorption, ion exchange,
membrane and electrochemical technologies but these techniques are expensive,
not environment friendly and usually independent on the concentration of the
waste which are ineffective in very diluted solution.
Physical parameters such as pH,
temperature and conductivity influence the concentration of many pollutants by
altering their availability and toxicity. The temperatures at which
environmental samples are collected and of which physicochemical measurements
are made are important for data
correlation and interpretation (Tay et al., 2009). Also, at high temperatures
the toxicity of many substances may be increased. In addition to microbial
activities, within an aquatic medium, temperatures and pH are two important
parameters that govern the methylation of elements such as Lead and mercury
(Von Loon, 1982). The electrical conductivity (EC) is also useful indicator of
mineralization in a water body which has a correlation with the Total Dissolved
Solids (TDS) in the water body.
In several mining communities in
Ghana, groundwater has become the drinking water source of choice due to
extensive contamination of surface water by mining activities particularly
small scale illegal mining (Armah et al., 2011; Armah et al., 2010).
With the discovery and the eventual
extraction of gold in the area by Newmont Ghana Gold Limited, the activities of
galamsey operators have increased in the area. It is their activities on the
quality of surface water including the Akantansu and Sintim Rivers in the
Asutifi district that serves as the basis of this research.
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