Assessment of Contamination of Underground Water Sources in Enyigba Pb-Zn District, South Eastern Nigeria using Metal Enrichment and Pollution Indices

Paulinus N Nnabo

doi:10.18483/ijsci.825

Abstract

Samples were collected from four (4) underground water sources in Enyigba Pb-Zn mining district, near Abakaliki in southeastern Nigeria. The samples were acidified to stabilize the metals for periods more than four days without the use of refrigeration. The acidified water samples were analysed by a commercial laboratory at Projects Development Institute (PRODA), Enugu using Atomic Absorption Spectroscopy (AAS). The elements determined by this method are lead (Pb), zinc (Zn), copper (Cu), arsenic (As), cadmium (Cd), nickel (Ni), manganese (Mn) and cobalt (Co). The result and analysis showed that metal enrichment index (MPI) of As, Cd, Pb and Ni are very high in the groundwater samples, indicating high degree of contamination compared to WHO permissible limits. All these metals contributed to high degree of contamination based on metal pollution index (MPI). The calculated metal enrichment and pollution indices show values that indicate that under the prevailing conditions and environmental regulations in Nigeria, the Enyigba mining district would face major and hazardous discharges of these metals to other water sources in the area.

Highlights

The study area (Figure 1), 14 km southeast of Abakaliki, covered the Pb-Zn mining district of Enyigba and its surrounding villages of Ameka, Ameri and Ohankwu all in Ebonyi State, southeastern Nigeria
The acidified water samples were analysed by a commercial laboratory at Projects Development Institute (PRODA), Enugu using Atomic Absorption Spectroscopy (AAS)
High content of Cd was only obtained from Enyigba Primary School borehole with concentration of 0.5 mg/l, and 167 times above the WHO (2011) maximum permissible limit of 0.003 mg/l for water quality (Table 4, Figure 6)

Summary

Introduction

The study area (Figure 1), 14 km southeast of Abakaliki, covered the Pb-Zn mining district of Enyigba and its surrounding villages of Ameka, Ameri and Ohankwu all in Ebonyi State, southeastern Nigeria. The deposit of Pb-Zn sulphides (galena and sphalerite) in Nigeria have been known for a long time but have only been exploited in the past on a very small scale. The deposits are localized in the Cretaceous sediments along 600 km long belt within the Benue Trough, a sediment filled intracratonic basin extending from Ishiagu (South of Abakaliki) north-eastwards to Gombe (Farrington 1952, Orazulike 1994). Mining of the ore has been carried out for a long time by both the natives, for local uses as cosmetics, and foreign companies, for export. Since the discovery of and mining of Pb-Zn deposits in Abakaliki and its environs in the early 1900s, data existing on the impact of their mining on the environment are very rare

Methods

Discussion

Conclusion