Determination of Selected Heavy Metals in River Mukurumudzi to Establish Potential Contamination from Land Based Activities and Sources

Master's Thesis from the year 2018 in the subject Environmental Sciences, grade: 76, , language: English, abstract: Rivers are the major sources of water being used in cities and its environs. This water may either be treated or untreated. River banks could be very busy, varied activities ranging from farming to industrial activities and other domestic household activities are conducted. The present study aimed at investigating the potential sources of selected heavy metal contaminants in River Mukurumudzi, Kwale County. Water and sediments were sampled in four points along the river impacted by mining, human settlements and agricultural activities for three different seasons. The samples were analyzed for Iron, Lead, Cadmium, Copper and Arsenic using an AAS. Sediment quality was also analysed by the calculation of CF and I-geo values. Interpretation of results was conducted using Minitab statistical software and Excel spreadsheets. The range of metals in water during the dry season was Fe (0.19-0.32) mg/l, Pb, Cu, Cd and As were below the detection limits. The range of metals in water during the short rain was Fe (0.12-1.25) mg/l and BDL for all other analysed metals. The range of metals in water during the long rain season was Fe (0.07-1.82) mg/l, Cu (0.08-0.11) mg/l and BDL for all the other analysed metals. The range of metals in sediments during dry season was Fe (0.13-1.44) ppm, Pb (0.08-0.54) ppm, and BDL for all other analysed metals. The range of metals in sediments during short rain season was Fe (0.23-1.73) ppm, Pb (0.12-0.27) ppm, and BDL for all other analysed metals. The range of metals in sediments during the long rain season was Fe (0.25-2.75) ppm, Pb (0.09-0.34) ppm, Cu (0.10-0.14) ppm, and BDL for all other analysed metals. The CF values for sediments were all <1 which indicated low contamination. The I-geo values of metals in sediments were all <1 suggesting the sediments are practically unpolluted. The concentrations of metals in water were all within the NEMA, KEBS and WHO limits thereby indicating non-contamination. River Mukurumdzi water and sediments are not contaminated by heavy metals. However, there is need for the land-based activities to be assessed since elevation of metal concentration was observed during the rainy seasons because of run-off from these sources.

KEY WORDS: Heavy metals, AAS, BDL, Sediments and Water contamination, I-geo and CF