Assessment Of Heavy Metal Pollution In Soils And Water Of Samburu County, Kenya

ABSTRACT

Heavy metal pollution in soil and water arising from anthropogenic sources continue to pose a great challenge to human and animal population. In Samburu County conflicts arising from cattle rustling, military trainings in the county which have led to heavy use and disposal of arms, a growing population without proper sewerage facilities, increase in the number of aging automobiles and fertilizers from the wheat and barley farms in the highlands of Lorroki are the biggest contributors of heavy metals in the soil and water. Since heavy metals in the environment have continued to increase there is need to determine their levels in the environment for efficient environment management, hence the need to determine the levels of heavy metals in the soil and water in Samburu County. The heavy metals that were analyzed included Zn, Pb, Cr, Mn and Cd. 136 water samples and 176 soil samples were collected from the agricultural, residential and commercial areas of Kirisia and Lorroki Divisions of Samburu County. The soil samples were digested using aqua regia while the water samples were digested using nitric acid and hydrochloric acid. The soil and water digested samples were analyzed for heavy metals using atomic absorption spectroscopy. The data was analyzed using ANOVA. From the results, means of Cd, chromium, manganese, lead and zinc in wells in Kirisia in mg/l were 0.010±0.000, 0.050±0.010, 0.080±0.010, 0.130±0.080 and 0.050±0.010 mg/l respectively. While the mean levels in dams were 0.020±0.010, 0.050±0.010, 0.050±0.010, 0.060±0.030 and 0.050±0.010 mg/l. Similarly the mean of the same metals in boreholes in Kirisia were BDL, 0.030±0.010, 0.090±0.020, 0.320±0.110 and 0.020±0.010 mg/l respectively. The mean levels of Cd, Cr, Mn, Pb and Zn in Lorroki in wells were 0.003±0.001, 0.030±0.010, 0.040±0.010, 0.052±0.010 and 0.030±0.010 mg/l while the mean in dams were 0.004±0.001, 0.040±0.010, 0.050±0.010, 0.230±0.050 and 0.040±0.010 mg/l respectively. The mean levels of the same metals in soils in the Kirisia and Lorroki divisions in mg/kg were 0.60±0.14, 2.65±0.30, 17.44±1.02, 55.33±5.93 and 376.35±46.64 mg/kg while the mean levels of the respective metals in the soils in Lorroki in mg/kg were 0.570±0.13, 3.690.390, 21.91±1.82, 51.80±4.16 and 265.95±59.75 mg/kg. The mean levels of the Pb in all the water sources were found to be above the WHO maximum contamination level. With the exception of the level of lead in dams and wells in Kirisia and Lorroki Divisions, there was no significant different between the levels of all the other analyzed heavy metals in dams and wells in Kirisia and Lorroki Divisions. This study provides an opportunity for frequent monitoring of heavy metals in this environment and hence providing an opportunity to the stakeholders to help in curbing heavy metal pollution in Samburu County. Though most levels of the heavy metals were within the WHO (2003) maximum recommended contamination level, the level of lead in water was above this recommended level hence the need to put mechanisms in place to reduce the contamination due this heavy metal.