ORGANIC CONTAMINANTS AND HEAVY METAL ANALYSIS IN THE GROUNDWATER OF KERIO VALLEY WATER BASIN, BARINGO COUNTY, KENYA

Abstract

Many harmful effects of human activities below the surface of the earth have a negative impact on groundwater quality, as many mineral- and oil-rich places can attest to. The impacts may include enhanced risks of cancer and genetic aberrations. Therefore, research on the determination of physico-chemical characteristics, heavy metals and organic pollutants in groundwater from boreholes of Kerio Valley water basin near commercial oil exploratory wells is fundamental. A solid phase extraction technique was used to extract water samples from specific boreholes in the Kerio Valley water basin of Baringo County. The water samples were then analyzed for organic contaminants using a gas chromatograph interfaced with a mass spectrograph detector. Out of the 4 boreholes sampled, 3 contained benzene derivatives, mainly xylene, 1,3,5-trimethylbenzene, 1-ethyl-3-methylbenzene, 1-methyl-2-propylpentylbenzene, and polycyclic aromatic hydrocarbons such as naphthalene, phenanthrene, fluoranthene, azulene, and pyrene. Furthermore, long-chain hydrocarbons were found in varied quantities in all groundwater samples. Benzene derivative concentrations ranged from 2.84 ± 1.04 to 20.47 ± 1.53 ppm. However, polycyclic hydrocarbons exhibited the highest concentrations of all organic pollutants, with pyrene giving a concentration of 23.14 ± 2.05 ppm, fluoranthene (18.54 ± 1.89 ppm), phenanthrene (14.13 ± 1.60 ppm) and anthracene (12.72 ± 1.20 ppm). In accordance with the results, 3-methyl-2,3-dihydro-1-benzofuran predominated in all samples, with concentrations ranging from 0.070 ± 0.28 to 9.390 ± 1.12 ppm compared to 0.28 ppm WHO permitted limits. Heavy metals were analysed in groundwater samples using atomic absorption spectroscopy (AAS). The results showed that the boreholes have remarkably high concentrations of lead, cadmium, and chromium. Interestingly, Pb was found to have a concentration profile ranging from 0.26 ± 0.01 to 10.76 ± 0.22 ppm, Cd ranges from 0.22 ± 0.01 to 0.29 ± 0.03 ppm, Mn posting high concentration of 1.86 ± 0.04 ppm in KV8 water sample, while Cr concentration ranged from 0.09 ± 0.002 to 0.37 ± 0.03 ppm. According to the results of this study, borehole water in the Kerio Valley basin is contaminated and may be hazardous for human consumption. The reported concentration levels were several times greater than the guidelines of the United States Environmental Protection Agency (USEPA) and the World Health Organization (WHO). Consequently, it is vital to establish a policy framework for the assessment and monitoring of water quality in the region, as well as propose intervention methods to assure a clean water supply for the well-being of inhabitants of the Kerio Valley water basin.