Land-Based Activities as Pollution Sources on Fresh Water Resources: A Case Study of Selected Heavy Metal Contamination in River Mukurumudzi, Kwale County
Ojwang, Loice M.
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Pollution of water-body ecosystems by heavy metals through uncontrolled anthropogenic activities lead to serious ecological problems in many parts of the world. These metals continue to accumulate to high toxic levels as they are discharged into water-bodies from agricultural activities, industrial and domestic wastes, and mining operations. This study focused on assessing the concentration of selected heavy metals (Fe, Pb, Cu, Cd and As) in the waters and sediments of River Mukurumudzi in Kwale County, Kenya. Four sampling points along the course of the river were purposely chosen owing to their proximity to identified land based pollution sources, these were titanium mining sites, large scale sugarcane plantations, human settlements and a control site. Samples were collected in three different seasons (long rain, short rain, and dry season). The heavy metals were analyzed using Atomic Absorption Spectrophotometer (AAS). The results showed that the level of Fe and Cu in water was the highest during the rainy season while all the other metals were found to be below detectable limits. In sediments, Fe (0.64 mg/L, 1.97 mg/L, 0.33 mg/L and 0.21 mg/L), Cu (0.1 mg/L, 0.14 mg/L, 0.14 mg/L and 0.1 mg/L), and Pb (0.14 mg/L, 0.21 mg/L, 0.12 mg/L and 0.33 mg/L) were detected at Shimba Hills, Nguluku, Bomani and Gazi consecutively. The concentrations of metals in water were found to be within the NEMA and WHO safe limits. Though River Mukurumudzi is not contaminated with the selected heavy metals it is established that the anthropogenic activities along the river are contributing some of the heavy metals. As such, this study recommends that conservation measures be put in place to avoid contamination of the river.