GRUPO EXPERIMENTAL COLEGIO MANUEL J CALLE

Abrahim, (2005) and Abrahim and Parker, (2008) presented a modified and generalized form of the Hakanson, (1980) equation for the calculation of the overall degree of contamination as expressed in equation 3.6. Investigation for Contamination degree is very important because it shows at a glance the degree of contamination of the sample areas for all the metals analysed (Casper et al., 2004). It can be used to generally classify the soil with respect to the

184 level of contamination. Table 4.20 shows the categories of classification of contamination degree, while appendixes 19a and 19b shows the contamination degree for the samples analysed in dry and rainy seasons respectively. Quality of soils and sediments are shown in tables 4.21 and 4.22 for dry and rainy seasons respectively.

Table 4.20: Categories of Contamination Degree based on Abrahim and Parker, (2008)

mCd Index Remark

mCd < 1.5 Nil – very Low degree

1.5 ≤ mCd < 2 Low degree of contamination

2 ≤ mCd < 4 Moderate degree of contamination

4 ≤ mCd < 8 High degree of contamination

8 ≤ mCd < 16 Very high degree of contamination

16 ≤ mCd < 32 Exremely high degree of contamination

mCd ≥ 32 Ultra high degree of contamination

Table 4.21: Quality of sediments/ soils based on Degree of Contamination for dry season samples analysed.

%very low % Low %Moderate % High % Very high %ExtremelyHigh % Ultra High

82.75 1.72 6.89 8.62 - - -

Table 4.22: Quality of sediments/ soils based on Degree of Contamination for rainy season samples analysed

%very low % Low % Moderate % High % Very high % Extremely High % Ultra High 70.69 5.17 13.79 8.62 1.72 - -

185 The analysis of contamination degree show nill to high degree of contamination (< 1.5 to above 8), this implies low to high degree of contamination for the samples. High degrees of contamination were observed around the mining fields of Alibaruhu, Amorie, Amanchara, Mkpuma Akpatakpa, Enyigba and Ameka (Fig 4.83). This analysis corresponds with the various contoured plot and analysis on the overall level of contamination in the area, and shows the same trend for both dry and rainy seasons. The analysis of contamination degree also shows that there are no cases of extremely high and ultra high contamination in the mining fields of the study area.

Fig 4.83: Distribution of Contamination Degree in soils/ stream sediments analysed.

186 CHAPTER FIVE

SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 5.1 Summary

Hydrogeological and geochemical assessment of the lead – zinc mining areas of Abakaliki, Ebonyi State, Southeastern Nigeria was carried out covering a total area of about 794.2km². These areas include Enyigba, Mkpuma Akpatakpa, Ameka, Amorie, Amanchara and Alibaruhu communities where active and abandoned mines are located.

One hundred and sixteen water samples, comprising forty – seven from groundwater sources and sixty- nine from surface water sources were analysed using Atomic Absorption Spectrophotometric and Ultra Violet / Visible Spectroscopy. One hundred and sixteen soil / stream sediments were collected and subjected to geochemical analysis using Atomic Absorbtion Spectrophotometric method, and pedologic safety analytical tools including Effect Range Low (ERL), Effect Range Median (ERM), Pollution Index (€), Geoaccumulation Index (Igeo), Contamination Factor (Cf), Pollution Load Index (PLI), and contamination degree were used to assess the impact level of mining activities in arable soils.

One hundred and ten hand dug wells were sampled for geohydrological studies while surface geological mapping (including the studies of rock types and fracture pattern) was done. This study has led to the following findings:

Geologically, the area is underlain by shales, limestone, siltstone, sandstone and mudstone. The rocks has been affected by tilting and fracturing genetically linked to the Santonian Orogeny, which has induced secondary porosity on the shales, resulting to the formation of semi confined aquifer in the area.

The analysis of fracture in the area shows a major NW – SE and minor NE – SW fracture system. These fracture system controls groundwater movement. Groundwater

187 flowstudies reveals predominance of recharge area in the axis of Abakaliki metropolis while the Enyigba, Ameka, Amorie, Alibaruhu axis are the discharge areas.

Results of hydrochemical analysis revealed that Ca²⁺, Mg²⁺, Fe²⁺, K⁺ ,Na⁺ (cations) and Cl^-, SO₄^2-, NO₃^-, HCO₃^- (anions) are the major hydrochemical constituents while Al³⁺, Mo²⁺, Pb ²⁺,Cu ²⁺,Hg²⁺, Cr²⁺, Ni²⁺, Cd²⁺, As³⁺, Ag⁺, Mn²⁺ and Se^2- are the trace constituents.

Concentrations of Cl^-, SO4

2-,CO3

-,Fe²⁺, Mn²⁺, Pb²⁺, Cr³⁺, Ni²⁺, Cd²⁺, As, Ag⁺, and Se^2- are above the WHO, 2011 permissible guidelines for drinking water, espacially for surface water and areas close to the active mines. However, the Ameka and Mkpuma Akpatakpa mining areas recorded higher concentrations of the geochemical constituents. Physical parameters indicate acidic to slightly basic waters for the areas. The abandoned mines showed considerably lower concentrations than the active mines.

Geochemical investigation of stream sediments and soils show Intermediate Contamination (IC) to Poor Contamination (PC ) for Ag, Cd and Hg using the Effect Range Low (ERL) and Effect Range Median (ERM); Cd, Hg and Ag show Significant Contamination (SC) using the Pollution Index (€); Cd show Heavy Contamination (HC) while As show Moderate Contamination (MC) using the Geoaccumulation Index (Igeo); Cd show Considerable Contamination factor (CC), while As show Moderate Contamination factor (MC) using the Contamination Factor (Cf). Pollution Load Index (PLI), show Moderate Pollution (MP) for As and High Pollution (HP) for Cd, while assessment of contamination degree show very high degree of contamination in the Mkpuma Akpatakpa and Ameka areas. The area is prone to chronic health and environmental hazards.

188 5.2 CONCLUSIONS

The following conclusions have been drawn from this study. The area is underlain by shales, limestone, mudstone and lenses of sandstone. These shales have been deeply fractured, with major trend in the NW – SE direction. This fracture pattern controls the groundwater movement and hydrothermal enrichment of minerals. These fractured shales are of great hydrogeologic and hydrologic significance since they form semi - confined aquifers which are the major aquifer units in the area, and controls groundwater flow. Groundwater flow direction indicates predominance of recharge area in the axis of Abakaliki metropolis while the Enyigba, Ameka, Amorie, Alibaruhu constitute the discharge areas. Hydrochemical analysis shows that concentrations of Cl^- , SO₄^2-,CO₃^-,Fe²⁺, Mn²⁺, Pb²⁺, Cr³⁺, Ni²⁺, Cd²⁺, As, Ag⁺, and Se^2- are above the WHO, 2011 permissible guidelines for drinking water, especially for surface water and areas close to the active mines. Safest water sources for various domestic uses are located around Nkwegu, Idembia, Amezekwe, Ndiechi and Umuigwe.

Water sources from area about 7 km radius from active mines are heavily polluted and hence considered unfit for many domestic uses, especially for drinking. Alternative sources of of water supply would be provided for the inhabitants of such areas.

Geochemical assessment of soils and stream sediments using six different pollution indices showed high degree of contamination for Ag, As, Pb, Hg and Cd (in the order of increasing pollution indices). This implies that arable soils around the mining areas (about 5 km radius) are not suitable for food crop production as biomagnification can occur in the food chain. Hence agricultural activities should be concentrated in safe areas to minimize the risk of potential health hazards. Assessment of contamination degree show higher contamination degree for the Mkpuma Akpatakpa and Ameka areas than the Enyigba and Amanchara areas. The adverse socio – environmental implications of mining in the area

189 includes destruction of vegetation, badland development, pollution, ecological disturbance system, destruction of buildings and health hazards.