Concentration of selected nutrients and heavy metals in soils in tea farms and water from Nyamasogota River, Kisii County, Kenya
Omwancha, P. Nyaboke
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The issue of water contamination and quality dilapidation in Kenya is more and more becoming a menace to the natural water resources due to modern methods of farming and industrialization which have resulted in water pollution especially in rivers. River Nyamasogota provides water for growing crops and for domestic purposes. The river passes through the areas that have many tea farms where fertilizers are heavily used and hence polluted by inorganic, organic and microbial substances. The waste effluents from tea factories also drain into the river. This research therefore aimed at establishing the levels of lead, copper, phosphates and nitrates in both river water and tea soils in comparison with the limits set by World Health Organization and Kenya Bureau of Standards. Variation of phosphates, nitrates, lead and copper were investigated in river Nyamasogota and adjacent farms during dry and wet seasons. Sampling was done at various points along the river Nyamasogota and randomly selected section of tea farms, upper tea farms and adjacent land in the months of February to April 2016. Water samples were filtered using whatman filter paper, digested and then analyzed while soil samples were dried, ground, sieved, digested using 30% hydrogen peroxide and then analyzed. Analysis using UV-VIS spectrophotometer was used to determine the levels of nitrates and phosphates while heavy metals were studied by Atomic Absorption Spectrophotometry technique. ANOVA, paired sample and one way sample t-tests were used for analysis. Results for two seasons ranges as follows: Pb in soils (0.139±0.026 to 0.279±0.024) mg/g. Pb in river Nyamasogota water (0.100±0.015 to 0.202±0.034) mg/l. Cu in soils (0.045±0.032 to 0.243±0.037) mg/g. Cu in river Nyamasogota water (0.127±0.016 to 0.312±0.013) mg/l. Nitrates in soil (0.031±0.025 to 0.626±0.022) mg/g. Phosphates in soils (0.045±0.021 to 0.0231±0.017) mg/g. Nitrates in river Nyamasogota water (0.206±0.021 to 0.358±0.015) mg/l. Phosphate in river Nyamasogota (0.232±0.021 to 0.524±0.023) mg/l. From the results the mean values of copper and phosphates in river Nyamasogota during wet season were above those set by KEBS and WHO (p<0.05). Based on the findings, the farmers should dig terraces to prevent runoff from tea farms since the land is sloppy and also intensify water purification before drinking water from river Nyamasogota in Kisii County. Farmers should also be educated on the impact of applying excessive phosphate based fertilizers on water quality alternatively they can use organic ones.