Abstract
Heavy metals’ availability and accumulation along the food chain pose public health risks. Water, sediment and plant samples were collected from selected sampling sites along Sosiani River, Uasin Gishu County, Kenya. The sediment and plant samples were dried in the oven at 50°C to constant weight and digested in a mixture of acids according to standard procedures. The water samples, sediments and plants digests were analyzed for selected heavy metals using Atomic Absorption Spectrophotometer (model AAS Variant 200). The site near the Moi Teaching and Referral Hospital (MTRH) had the highest total heavy metals concentration in water: Cu (0.18 ± 0.04 ppm); Pb (0.46 ± 0.09 ppm) and Zn (0.70 ± 0.22 ppm) and sediments: Cu (1.62 ± 0.14 ppm); Pb (1.27 ± 0.17 ppm) and Zn (6.73 ± 0.88 ppm) respectively. Fractionation of heavy metals in sediments showed low percentage solubility (Cu 9.3%; Pb 8.5%; Zn 4.2%). Concentration of zinc in studied plants was highest (3.60 ± 0.63 ppm), with a bioconcentration factor of 15.1 based on soluble zinc fraction. This indicates that conditions in the study area show preferential zinc metal uptake in plants and may lead to accumulation in exposed plants posing Zn exposure risks along the food chain. Suggestions are made for monitoring of heavy metals in food crops and aquatic organisms such as fish in the study area.
Highlights
Water is essential to life and because of its importance; the pattern of human settlement throughout history has often been determined by its availability [1]
There was no significant spatial and seasonal variation in mean copper concentration in water samples among sampling sites. This indicated that there were no significant point sources of copper in the study area or the river water dilution factor was high and the incoming pollution had no significant impacts on copper concentrations in water
It’s concluded that the total heavy metals studied in water and plant samples are within the accepted limits and others are above the WHO limits
Summary
Water is essential to life and because of its importance; the pattern of human settlement throughout history has often been determined by its availability [1]. The behaviour of metals in natural waters is a function of the substrate sediment composition, the suspended sediment composition, and the water chemistry [3]. During their transports, the trace metals undergo numerous changes in their speciations due to dissolution, precipitation, sorption and complexation phenomena [4,5] which affect their bioavailabilities [6]. Heavy metals are bioconcentrated or bioaccumulated in one or several compartments across food webs [8,9]. Metal bioaccumulation can be of importance from the public health point of view, especially for human at the end of the food chain. An important link in the transfer of heavy metals from soil/sediment to man is plants [10]
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