Heavy Metals Pollution Using XRF Spectrometry– A Case Study Of Kilimapesa Gold Mines Processing Plant, Narok County

Abstract

study determined the levels of concentrations of cadmium, arsenic, chromium, mercury, lead, copper and zinc in order to assess the extent of heavy metal pollution around Kilimapesa Gold mine processing plant in Narok County. A total of forty-one (41) samples, sampled from nineteen(19) sites, namely; nine (9) sub-surface soils, eight (8) sediments, fourteen(14) Sodom apple (Solanum incanum) leaves and ten (10) water samples, from the nearby river streams were analysed for heavy metal content using EDXRF and TXRF techniques. The sediments, soils and plants samples were dried, crushed, sieved and made into thin pellets. They were analysed using the EDXRF spectrometer available at the Department of Physics, University of Nairobi. Gallium was added to the water samples as an internal standard, mixed and pre-concentrated before analysis using the TXRF spectrometer at the Ministry of Petroleum and Mining Laboratories. The results of the metals concentrations levels in water samples (mg/l) were distributed as follows; Cd (< 4.4), Hg (< 1.0), As (< 1.5), Cr (< 6.5 - 391), Zn (< 3.0 -187), Ni (< 4.0 - 830), Pb (< 3.0) and Cu (< 1.1 - 470). The highest concentration was recorded at the confluence of the streams, this could be due to an accumulation of sediments at the convergence point. The levels in soil samples (mg/kg) were; Cd (< 3.00), Hg (< 1.9-23.5), As (14.6 – 935), Cr (111 - 406), Zn (61.5-156), Ni (24.4-164), Pb (26.6-148) and Cu (42.3-174. The variations of the metals concentration levels in Sodom apple (Solanum incanum) samples (mg/kg) were; Cd (< 3.0), Hg (< 1.9-3.2), As (< 1.1 - 2.0), Cr (< 3.0-10.0), Zn (24.5-40.9), Ni (< 2.0 - 14.3), Pb (< 2.0-7.2) and Cu (17.9-33.3). These concentrations in Sodom apple are comparable to those in other places apart from arsenic and lead, which may be attributed to mining activities in Lolgorian. There was a significant difference in concentration of the heavy metals among the three media sampled following ANOVA analyses. Heavy metals concentrations were recorded as highest in the soils, followed by plants and water samples, had the least concentration levels. Pearson's correlation for all trace elements of interest in Sodom apple (Solanum incanum) and soils was very weak except for mercury which had a strong relationship. The same trend is observed between soils and water and between water and plants, for all heavy metals of interest in this study, except for Zn and Ni, respectively. The Kilimapesa soils are moderately to extremely contaminated with these metals, according to results from pollution indices and geo-accumulation indexes analyses, that are greater than 1. The study recommends use of heavy metals bio-accumulators like water hyacinth in the waste disposal treatment ponds and enforcement of regulations to reduce contamination of the environment. More studies on the area should be done to determine the contributors to pollution and use of bioassay data and records from the health facilities for epidemiological study over time.