Determination of selected heavy metal levels in underground water and soil and analysis of water hardness sources in Nyatike-Karungu Divisions, Migori District, Kenya.

Abstract

Intensive mining activities and highly mineralised rock formations have a significant impact on both surface and underground water. Mining activities shuffle the rock formations creating fissures and cracks enhancing greater percolation and movement of water underground. Macalder mines(gold mining region) in Nyatike –Karungu Divisions was divided into two regions (Epicentre and surrounding).This research sought to determine the concentration levels of Zn, Cu, Pb, Fe, and water hardness levels and sources. Quantitative determination of heavy metal levels were performed using FAAS and water hardness determined using EDTA titration method. The interpretations of the analytical results were performed using Excel spreadsheet and SPSS statistical packages. The range of the mean metal concentration in water during the dry season was Zn (0.04-0.19) mgl-1, Cu (0.01-0.04) mgl-1, Pb (0.63-2.48) mgl-1, and Fe (0.44-1.63) mgl-1. The range of mean metal concentration in water during the wet season was Zn (0.03-0.37) mgl-1, Cu (0.01-0.05) mgl-1, Pb (0.51-4.02) mg-1 and Fe (0.44-2.43) mgl-1. The range of the mean metal concentration in soil during the dry season was Zn (0.08-2.64) ppm, Cu (0.2-1.12) ppm, Pb (0.22-2.28) ppm, Fe (0.50-2.00) ppm. The range of mean metal concentration in soil during the wet season was Zn (0.09-0.19) ppm, Cu (0.08-0.66) ppm, Pb (0.25-2.37) ppm and Fe (0.27-1.78) ppm. The pH of the borehole waters were determined in situ and ranged from 6.5-7.2 thus an average of 6.7. The range for the mean water hardness during the dry season was (75.83-658.6) mg/L of CaCO3 and wet season (71.60-585.83) mg/L of CaCO3. Concentrations of Zn, Cu and Fe were within the WHO water quality guidelines except for Pb levels that were above the admissible threshold. Nyatike-Karungu divisions lie along a geological fault line with volcanic igneous rock type, dolomite, limestone and dolerite rocks predominant. The net effect of the solubility of these rocks was the hardness of water in the boreholes and wells however, lake water samples showed low hardness levels ranging from (75.8-99.4) during dry season and (71.6-95.1) mg/L of CaCO3 during wet season.