Major Ion Chemistry and Quality Assessment of Groundwater in Maiduguri and Jere

Abstract

Hydro-chemical conditions of groundwater in the upper aquifer system around Maiduguri and Jere local government area of Borno state were investigated. The geochemical processes controlling the concentrations and evolutions of the major ions in the aquifer indicates that water rock interaction is the major control. The concentrations of CA, Mg, SO4, and HCO3 are likely resulting from resolution of gypsum (CaSO4. 2H2), dolomite (CaMg(CO3)2), halite (NaCl) and magnesium sulphate (MgSO4) occurring in the aquifer matrix. However, other possible sources such as respiration or oxidation of organic matter and reduction of sulfate are attributed to higher concentration of HCO3 observed in some samples. The relatively higher concentration of Na, and Cl in the groundwater are most likely due to dissolution of halite (NaCl) which are probably occurring in the aquifer matrix. The plot of Na versus Cl was used to understand the overall Salinity in the groundwater, which is identified to be due primarily to the buildup of two major constituents (Na and Cl). Na excess relative to Cl in the samples is probably as a result of ion exchange of Ca or Mg for Na in the water and clay minerals which may probably be present in the aquifer materials. The relative high concentration of magnesium and calcium in the groundwater are most likely due to dissolution of dolomite (CaMg(CO3)2) which could be most likely source of these ions in the groundwater, since the mineral has ions as it\'s constituent. The relative concentration of calcium and sulphate in the groundwater are most likely due to dissolution of dolomite (CaMg(CO3)2) which could be most likely source of these ions in the groundwater, since the mineral has ions as it\'s constituent. The relative concentration of calcium and sulphate in the groundwater is most likely due to dissolution of gypsum (CaSO4.2H2) which could be most likely source of these ions in the groundwater. Various classifications of groundwater in the aquifer (Ca-Na-HCO3, Na-Ca-HCO3 and Na-HCO3 are important for regional hydrogeochemical studies. The assessment of water quality for domestic consumption shows that all the samples two or more of the ions above the WHO recommended limit. TDS values were used to understand the suitability of the groundwater for domestic consumption. The groundwater is considered good for consumption.

Introduction

1. Introduction

Water is essential for life and socio-economic development. In Maiduguri, groundwater is the main source of drinking water, but increasing pollution from urbanization, poor waste disposal, and agricultural activities has compromised its quality. Monitoring groundwater quality is essential as it directly impacts public health.

2. Aim and Objectives

The study aims to:

• Identify chemical elements in groundwater.

• Analyze hydrochemical evolution and geochemical processes.

• Assess the suitability of groundwater for domestic use.

3. Study Area: Maiduguri

• Located in North-Eastern Nigeria, within latitudes 11°48’N to 11°55’N and longitudes 13°04’E to 13°14’E.

• Region is semi-arid with sparse Sahel vegetation and dominated by fine sand, silt, and clay.

• The area is flat with River Ngadda serving as the main drainage channel flowing into Lake Chad.

4. Geology and Hydrogeology

• Maiduguri lies in the Chad Formation, part of the larger Borno Basin, which has undergone various geological transformations.

• Major geologic units include:

  • Bima Sandstone (fluviatile origin)

  • Gongila Formation (marine/continental transition)

  • Fika Shales (marine origin)

  • Gombe Sandstone

  • Kerri-Kerri and Chad Formations

• The Chad Formation (youngest) consists of various clay and sandstone layers, forming aquifers critical for groundwater storage.

• Aquifers are divided into:

  • Upper, Middle, and Lower sandstone members (S1, S2, S3).

  • Intervening clay layers (CL1, CL2).

  • Groundwater is stored in confined and unconfined aquifers.

5. Methodology

• 32 borehole samples were collected from Maiduguri and Jere.

• Water samples were tested for physico-chemical parameters including:

  • pH, Total Dissolved Solids (TDS), Electrical Conductivity (EC)

  • Major ions: Na, K, Ca, Mg, Mn, Cl, SO?²?, HCO??

• Equipment: UV/VIS spectrometer, AAS (Atomic Absorption Spectroscopy)

• Preserved using nitric acid and stored in clean containers.

6. Results and Discussion

A. Field Results

• Water sample locations spanned areas like Mairi, Kaleri, London Ciki, Custom, Gwange, and Bolori.

• All samples were drawn from shallow boreholes at elevations ~320m.

B. Laboratory Results

• pH ranged from 1.2 to 7.8 (note: pH 1.2 is extremely acidic and abnormal; likely an error or anomaly).

• TDS: 57 to 1453 mg/l — higher values indicate greater mineral content.

• EC: 180 to 2930 µS/cm.

• Major ions:

  • Na: 9–70 mg/l

  • Ca: 23–540 mg/l

  • K: 11–49 mg/l

  • Mg: 0.33–171 mg/l

  • Mn: 0–9.5 mg/l

  • Cl: 18–114 mg/l

  • SO?²?: 5–110 mg/l

  • HCO??: 109.84–511.43 mg/l

• Most values were within WHO acceptable limits, except for localized anomalies.

7. Hydrochemical Evolution and Interpretation

• Na vs Cl: Linear correlation suggests a common source—likely halite (NaCl) dissolution.

• Mg vs Ca: Progressive linear relationship indicates dolomite dissolution as the source (CaMg(CO?)?).

• The evolution of groundwater chemistry is influenced by rock-water interaction and infiltration processes.

8. Geological and Structural Insights

• The basin is affected by fault systems (NE-SW and NW-SE trends), influencing sediment deposition and groundwater flow.

• The structural complexity (horsts and grabens) plays a role in aquifer distribution and groundwater quality variability.

9. Previous Work

• Extensive past research has been conducted on the Chad Basin geology and hydrogeology, including works by Matheis (1976), Kogbe (1976), Reyment (1965), and various reports by Nigeria’s Federal Ministry of Mines and Power.

• Prior research confirms the presence of three major aquifers within the Chad formation that provide groundwater for the region.

Conclusion

ThestudyareaislocatedinnorthernpartofMaidugurimetropolis,andsomepartof Jere local government area of Borno state. The geology of the area is sedimentary, the study was conducted to determine the element present in the groundwater and theirimplicationonhumanenvironmentandalsoforthedeterminationofqualityof water consumed by people living within the city. The physical and chemical analyses carried out on the water samples where to determinethePH,totaldissolvedsolid(TDS), electricalconductivity(EC),calcium, magnesium, potassium, sodium, sulphate, bicarbonate, manganese, chloride. The result of the physical and chemical quality of the groundwater from the study area were obtained. The data obtained from the chemical analysis were presented in form of scatter (X, Y) or bubble chart to show relationship between two different parameters. Theanalysisoftheresultshowsthatthedissolutionofhalite,dolomite,gypsumandcalcitethatmayoccurwithintheaquifermatrixcouldberesponsiblefortherelease ofsomeofthemajorionobserved.Therelativelyhighconcentrationofsomemajor ions in some samples could be attributed to ion-exchange processes.

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Copyright

Copyright © 2025 Abdulsalam Muhammad, Musa Mallam Aji, Dede Lawan Dahiru, Muhammad M. K., Yakubu Mohammed, Boyoma A. M., Abdullahi Banjaba Lawan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.