ASSESMENT OF GROUNDWATER QUALITY WITHIN SOME SELECTED DUMPSITES IN KEFFI, USING GEOCHEMICAL AND GEOPHYSICAL METHODS.

Abstract

Groundwater quality of some selected dumpsites (four) within Keffi town was studied using the electrical resistivity tomography (ERT) method of geophysics and geochemistry. The geology of the area was determine using field observations and related literature which enables the production of a modification to produce updated map of the study area using Arcmap 10.5, from the boundary extraction, the area has three major rock types namely: Migmatite Gneiss, Banded Gneiss and Quartzo-Feldspathic Schist. The acquired data of geophysics were obtained using the dipole-dipole method via lateral profile paths along preferred portions of the dumpsites, the analyses were carried out using win resist resistivity inversion software to produce 2D resistivity structure-depth models of the area which enables the zone delineation of the leachates zones. The leachate zone was seen as the portion with very low resistivity which ranges from 5.3Ωm – 25.2Ωm (denoted as blue). Other layers include the top soil which ranges from 30.6 Ωm – 46.6 Ωm (denoted as green), fractured basement from270 Ωm – 650 Ωm (denoted as reddish brown) and weathered basement from 650 Ωm to 1564 Ωm (denoted as paled green). The result of the elemental composition for both anions/cations and heavy metals ranges from Mg²⁺ (7.32-105.4mg/L) Ca²⁺ (8.8-308.6mg/L) Na²⁺ (2.5-50mg/L) K²⁺(14-41mg/L) Cl⁻ (11.98 – 209 mg/L) HCO₃⁻ (36 -520 mg/L) SO₄²⁻ (2 – 494 mg/L) NO₃⁻ (4.1 -172 mg/L) Fe (BDL-2.24mg/l) Cu(0.01 – 1.046mg/l) Cr (0.049-0.898mg/l) Cd (0.002 -0.302mg/l) Zn(0.049 – 2.609mg/l) . Piper trilinear diagram, and Schoeller diagram revealed three water facies types: Ca/Mg-SO4/Cl, Na/K-SO4/Cl, Ca/Mg-HCO3. The Gibbs plots reveals ion exchange as a result of rock water interaction majorly. The physio-chemical parameters carried out was for the 27 groundwater point samples. The results showed that the waters were slightly acidic to slightly alkaline (3.5 ≤ pH ≤ 7.5), fresh to brackish (124 ≤ TDS ≤ 1225), temperature was 28 - 37˚C and characterized by electrical conductivity values ranging from 172 to 143054 µS/cm. The analyzed parameters, except for Mg2+, NO-3, K2+, Fe, Cd, Cr were within the WHO, USEPA, and NSDWQ recommended standards. The computed contamination factor (CF ≥ 6) results indicated that twelve (12) water samples were highly contaminated with cadmium and two (2) with Chromium. The index of geo-accumulation (Igeo) results showed that one sample were slightly contaminated (Igeo ≥ 3) with Cu and Zn while the computation of pollution load index (PLI) reveals a slightly range of pollution (1 ≤ PLI < 2) conditions in four samples while the remaining 23 are all unpolluted.

Keywords: Heavy Metals, Physio-chemical, Hydrogeochemical Facies and Municipal Waste