Analysis of organic contaminants and the physico- chemical properties of borehole water of maili-nne estate and sosiani village, Uasin Gishu cCounty, Kenya.

Abstract

The noxiousness of pesticides as well as their harmful environmental effects have generated interests in the identification and quantification of organic contaminants in borehole water. These contaminants can move from agricultural land or poorly managediv sewerage systems and get into drinking water by surface runoff or by leaching into groundwater. The study sought to analyze the organic contaminants and their effects on physico-chemical parameters of borehole water of Maili-nne; a residential area and Sosiani, an agricultural area. This was through detection of organic contaminants in borehole water; quantification of the detected organochemicals; and establish the impacts on the physico-chemical properties of borehole water of Maili-nne and Sosiani areas. Fifteen boreholes, five at Maili-nne (MB1-MB5) and ten at Sosiani (SB6-SB15) were systematically selected and water sampled during the dry and the wet seasons. Organic contaminants were analysed by detection and quantification of organic pesticides and plasticizer based on retention times by High Performance Liquid Chromatography (HPLC) and Gas Chromatography–Mass Spectroscopy (GC-MS) in correlation to computed element libraries for quantification. Their impact on pH, turbidity, colour and Biological Oxygen Demand (BOD) were probed using pH meter, turbidity meter, colour disc and BOD meter, respectively. The nutrients, sulphates and nitrates were analyzed using ultraviolet spectroscopy (UV-Vis). Diazinon was detected in boreholes SB9, SB12 and SB13, with highest level of 2.21 mg/L during the dry season and 1.52 mg/L in the wet season. Fenitrothion was detected in MB1 (0.145 mg/L and 0.191 mg/L) during the dry and the wet season, respectively. Malathion was found in SB6 and SB15 at 0.207 mg/L and 0.940 mg/L, respectively only during the dry season. Cyhalothrin concentration in MB1, SB7 and SB9 were 0.11, 1.25 and 1.47 ppm, respectively during the dry season and 1.37, 1.31 and 1.21 ppm, respectively during the wet season. The concentration of bis (2-ethylhexyl) phthalate in the 15 boreholes ranged from 0.00 μg/L to 0.172 μg/L. Dimethoate was only detected in Sosiani (SB7) during the wet season. Sulphates concentration ranged between 0.00 -28.3 mg/L during the dry season and 1.06 - 66.44 mg/L during the wet season in Maili-nne and Sosiani. Nitrates concentration ranged between 0.31 - 22.8 mg/ L in the dry and the wet seasons. Physico-chemical properties of the water were found to be higher and others lower than WHO standards. The pH of the borehole water was in the range 5.45 - 5.92. Turbidity ranged between 1.32 - 3.08 NTU and 1.23 - 6.42 NTU during the dry and the wet seasons, respectively. BOD values ranged from 1 - 40 mg/L in the wet season and 0 – 8mg/L during the dry season and were significantly lower in Sosiani than in Maili-nne during the wet season. It can therefore be concluded that residues of some organic contaminants were above the WHO standards leading to decrease of water pH during the dry season beyond WHO limits (pH 6.5). The study also established that there was a positive significant correlation between presence of organic contaminants and deviation of physico-chemical properties (p=0.016, rho=0.68) in Maili-nne and Sosiani. In this regard the borehole water in the study areas should be treated and awareness be made on the impacts of pesticides use.