ABSTRACT
An integrated geological, geo-chemical and geophysical studies were carried out to investigate the concentrations of potentially toxic elements in groundwater within Bariki and environs, North Central Nigeria, in order to ascertain the effect of mining on the water quality. The investigation involves surface geological mapping of Bariki and environs on a scale of 1:12,500, groundwater level mapping, Determination of toxic elements concentration using Atomic Absorption Spectroscopy (AAS) and geo- electrical sounding. The lithology at every outcrop was identified on the basis of textural and visual inspections of mineral composition using hand lens and further refined by petrographic examination which reveals that the area studied is dominantly schist, granite and amphiboles schist, other rock bodies includes gneiss, quartzites and localized muscovite schist. The groundwater level mapping (Surface water level, depth of the well and elevation above sea level) were recorded. Hydraulic head of each well was calculated and the groundwater flow map was also generated indicating NW, SE and SS flow directions. The physical parameters measured in-situ were Temperature (T), pH, Electrical Conductivity (EC) and Total Dissolved Solid (TDS) using a multifunctional TDS/EC/pH/TEMP water quality meter tester, pH shows slightly low values of 6.22, 6.24 and 6.31 at BKW L2, BKW L3 and BKW L5 when compare to WHO and NSDWQ standards. Out of the ten toxic elements analysed, Cadmium (Cd), Chromium (Cr), Cobalt (Co), Copper (Cu), Iron (Fe), Lead (Pb), Manganese (Mn), Nickel (Ni), Zinc (Zn) and Arsenic (As), only Cadmium 0.075 ppm, Manganese 0.73 ppm, Lead 0.037 ppm and Iron 22.71 ppm were found to be above WHO and NSDWQ standard. Computed Metal Pollution Index (MPI) of 135.5002 indicates the groundwater is highly polluted from multi-metal effect. The subsurface apparent resistivity decreases in both NW and SE direction of groundwater flow. An active mine site upsets the NW, SE and the resultant SS decrease in heavy metal concentration. This implies that groundwater pollution in Bariki and environs is attributed to mining activities.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the Study
Groundwater is subsurface water beneath water table in saturated soils and geologic formations (Unuevho et al., 2016). It is one of the natural resources that support human existence and other lives on earth (Ajusa, 2003). Groundwater is exploited from boreholes and hand dug wells in urban and semi urban areas for domestic, agricultural and industrial usage. The chemistry of groundwater is influenced majorly by aquifer mineralogy, the residence time and dominant anthropogenic activities Amadi and Nwankwala, (2013). Groundwater pollution is a gradual degradation in water quality through the addition of chemicals and pathogens to a level that constitutes health hazards, and adversely affects domestic and agricultural products, as well as industrial utilization (Akhilesh et al., 2009). In recent years there is growing concern on the impact of anthropogenic activities on groundwater quality Amadi and Nwankwala, (2013). Water polluted by toxic element increases the risk of hypertension, skin cancer, Kidney failure, liver dysfunction and neurological diseases (Unuevho et al., 2016). Virtually any activity that releases chemicals or industrial wastes to the environment has the potential to pollute groundwater. Among such chemicals and wastes is heavy metal. These are metallic elements that have a relatively high density and become toxic or poisonous at high concentration. They include Cadmium (Cd), Chromium (Cr), Cobalt (Co), Copper (Cu), Iron (Fe), Lead (Pb), Manganese (Mn), Nickel (Ni), Zinc (Zn) and Mercury (Hg) (Adekoye, 2003).
Informal artisanal mining activities have been going on for some time now in Bariki. This constitutes a very high potential for polluting the groundwater in this vicinity via the release of toxic elements.
Heavy metal or toxic elements are natural component of the earth’s crust and are undegradable or indestructible. However, to a small extent, they enter our body through food, water and air. Some heavy metal such as Copper (Cu), Zinc (Zn), Iron (Fe) and Magnesium (Mn) are essential to life. But they become harmful and can be fatal at high concentration. Their occurrence in the environment results from the anthropogenic activities and natural processes such as rock weathering and volcanic activities (Amadi, 2011).
World Health Organization WHO (2010) opined that the accessibility to potable water is a fundamental objective in the fight against developmental challenges such as poverty, hunger, child mortality and maternal health. Rapid population growth and urbanization leads to an increase in demand and exploration for potable water (Lacerda, 1997).
The high level of toxic elements in natural water bodies can be attributed to some anthropogenic activities such as mining, oil spillage, farming and improper municipal waste disposal (Yusuf et al., 2017). According to the European Environmental Bureau (EEB, 2000) the major environmental problem associated with mining is the uncontrolled discharge of contaminated water (effluent) from the mines. Effluent discharge from gold mine is characterized by raised levels of toxic elements especially sodium of cyanide silver, mercury, arsenic and lead in soil and groundwater bodies (Adler and Rustler, 2007).
1.2 Statement of the Research Problem
Gold mining is accompanied by environmental degradation that bears adverse health effects in developing countries. Weaning gold from host rock in Bariki and environs involves mining, transportation, crushing, milling and washing. These activities do release toxic elements which infiltrate the groundwater in Bariki and environs, and thereafter get ingested by humans. The health implications of ingesting toxic elements necessitated the investigation of toxic element concentrations in groundwater within the vicinity of the Bariki mines. Such investigation is yet to be conducted in Bariki and environs.
1.3 Justification of the Research
Toxic elements are commonly found in concentrations that are harmful to human health in mining districts. Hypertension, Skin cancer, Kidney failure, Liver dysfunction, Neurological diseases are among health challenges that have been associated with ingesting heavy metal. Determination of toxic element or heavy metal concentrations in groundwater within Bariki is necessary to ascertain the potability of the water, with respect to past and present mining activities in the area.
1.4 Study Area
The study area is Bariki and environs. It is located in the southwestern part of Paiko Sheet 185NW on the scale of 1:50,000, North Central Nigeria. It lies between Latitudes N09° 29′ 00″ to N09° 30′ 00″ and Longitudes E006° 31′ 00″ to E006° 33′ 00″, within the Basement Complex of Northern Nigeria. Major Villages within the study area includes Bariki, Gado and Laitapi as indicated in figure 1.1 below.
1.5.0 Relief and Drainage
The study area is well drained by numerous seasonal streams and also dissected almost at the middle by the SW flowing river Maidna which empties her water in to river Chanchaga, which also empties it water in to river Gbako down-stream.
1.5.1 Climate and Vegetation
The study area is located within the tropical climate which is characterize by two season in a year (wet and dry seasons), the annual rainfall received within the region is less than 1000mm in The wet season last between April and September with a maximum downpour between months of July and August (Nigerian Metrological Agency, 2010). The dry season lasts between the month of October and March. Temperature varies within the region annually with the season. During the dry season temperatures are law because the sun is in the southern hemisphere. Minimum temperatures below 30⁰C are recorded during the harmatan period, which is late December and January in the following year. Maximum temperature is above 26⁰C. During the raining or wet season, the sun moves northwards from equator to the tropics of cancer. This result to high temperature because the sun overheads at noon. According to the Nigerian metrological agency (Nigerian Metrological Agency, 2010), the minimum temperature average above 26⁰C and maximum temperatures average of about 30⁰C particularly at mid-day between May and July. The vegetation is purely that of the Guinea savanna characterized by sparse vegetation and tall trees with patchiest of forest (Nigerian Metrological Agency, 2010).
1.5.2 Settlement and Land Use
Nucleated settlements characterize the study area. Pipe born water is unavailable and residence obtain water from hand dug wells and boreholes for drinking and domestic purposes. The borehole taps groundwater from regolith lithology or layer.
Plate I to V shows the various mine sites in Bariki.
1.7.0 Aim and Objectives of the Research
This project is aimed at ascertaining the quality status of groundwater in Bariki and environs, with respect to toxic element concentration.
The objectives are to:
1. Conduct the geological mapping of Bariki and environs on a scale of 1:12,500 in order to ascertain the water bearing units in the area.
2. Map groundwater levels to establish principal flow directions, using hand-dug well data.
3. Determine toxic element concentrations and its spatial distributions.
4. Obtain Isoresistivity map for top soil and weathered basement for pollution plume and aquifer evaluations.
1.6.2 Scope of Work The research work is limited to surface geological mapping, water level mapping, pH, Electrical conductivity and Total dissolve solid mapping, determination of concentration of toxic elements and geo-electrical sounding.
This material content is developed to serve as a GUIDE for students to conduct academic research
INVESTIGATION OF THE CONCENTRATIONS OF POTENTIALLY TOXIC ELEMENTS IN GROUNDWATER WITHIN BARIKI AND ENVIRONS, NORTH CENTRAL NIGERIA
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