ASSESSMENT OF MINERALOGICAL AND HEAVY METAL CONSTITUENTS OF GEOPHAGIC CLAYS IN PARTS OF ANAMBRA STATE, NIGERIA

Abstract

The mineralogical and chemical composition of in-situ geophagic clays were carried out in parts of the Niger Delta Basin,with the aim of determining the types, major and trace element constituents, and public health implications of the clays. Five samples were collected and subjected to X-Ray Diffraction (XRD) and X-Ray Fluorescence (XRF) analyses.XRD analysis revealed kaolinite (54 to 78 wt. %),chlorite (46 to 64 wt. %), namuwite (3 to 10 wt. %), kupletskite(4 wt. %), montmorillonite (4 to 5 wt. %),palygorskite (4 wt. %), quartz (22 to 46 wt. %) and albite (7 wt. %) minerals. The constituents observed from XRF analysis include SiO₂ (60.15 to 67.25 wt. %), Al₂O₃ (7.24 to 14.23 wt. %), Fe₂O₃ (3.22 – 4.61 wt. %), TiO₂ (0.47 – 0.91 wt. %), MgO (1.57 – 6.59 wt. %), CaO (1.62 – 2.87 wt. %), Na₂O (0.32 – 2.14 wt. %), K₂O (0.61 – 1.51 wt. %) and MnO (0.03 – 0.30 wt. %). When compared with average crustal abundance values, the samples from Enugwu-Agidi had higher SiO_2, TiO₂, MgO and MnO; Igbariam higher MnO; Nteje higher TiO₂, MgO and MnO; Isinyi-Nando higher MgO and MnO. The XRF analysis also revealed the following heavy metal concentrations; Zn (61.12 to 321.11 ppm), Cu (16.03 to 36.08ppm), Pb (13.29 to 24.1 ppm), Hg (0.02 to 0.06 ppm), Co (1.81 to 5.41 ppm), Ni (29.00 to 83.27 ppm), As (3.42 to 5.20 ppm), Se (<0.01 to 20.02 ppm), Cr (43.71 to 106.20 ppm), Cd (0.06 to 0.12 ppm) and V (79.58 to 220.49 ppm). Zn, Pb, Ni, As, Cr and V were found to be higher than the joint FAO/WHO maximum daily permissible limits for heavy metals in food and vegetables. An assessment of the levels of contamination of the heavy metals using index of geo-accumulation (Igeo), shows that Zn, Cu, Pb, Hg, Co, Ni, As, Cr, Cd and V (all with Igeo< 1) did not contaminate the clays. The study suggests that a safe remediation technique be put in place before consuming these clays.