Analysis of the levels of heavy metals in soil, plant, water, Sediment and urine samples around the Athi river region

Abstract

In this work. X-ray fluorescence analysis technique was used to analyze soils. plants. water. sediments and urine samples from a selected area in the Athi River town. From the analysis. dust from the electrostatic precipitator was found to have very low levels of chromium and 1ead. For the other elements. dust had high 1eve 1s , e.g. iron (7480.3 - 9670. 7 ppm) and manganese (404.0 - 595.5 ppm). However. the levels were found to be lower than those in the indigenous soil in this region e.g. iron (30180.4 - 53340.7 ppm) and manganese (1320.1 1960.5 ppm) . Overa 11. there was an increase in the 1eve 1s of these metals with distance from the electrostatic precipitator. Thus. the metals in the dust were noted to leach down suggesting they were likely to be available to plants. From the analysis of plant leaves. the concentrations of metals were found" to depend on the levels in the soil. soil type and the organic matter content except for zinc. The metals in the indi genous soi 1 appeared to be more available to plants than those in the dust. Leaves from the three plant species sampled had significantly different.levels of heavy metals suggesting that they had different physiological role. different tolerance or different mechanisms of absorption. In the case of the water samples from the Athi river, the pH values were found to be high (7.20 - 9.45). The concentrations of the metals encountered were also higher than the natural uncontaminated levels e.g. copper (4.6 -17.9 ppb) which was much higher than the reported uncontaminated values (0.2 - 2.2 ppb) for drinking water although they were lower than the W.H.O. highest acceptable values. It was noted that as the distance of the sampling point from the point where a given metal was being discharged increased, the concentration of the heavy metals decreased. This suggested that the river load was within what it could cope up with i.e. removed by the natural self purification of rivers through the process of precipitation and scavenging by microorganisms. The concentration of elements in sediments from the Athi river were found to be generally high, e.g. chromium (0 - 428.2 ppm), iron (4970.1 - 14520.3 ppm), manganese (313.2 -6410.0 ppm), copper (1.6 - 43.7 ppm), zinc (16.4 - 55.7 ppm), lead (3.3 - 32.7 ppm) and mercury (0 - 23.2 ppm). Despite this~ it was noted that that only a small percentage was in solution. This was probably due to the high pH of the water, low solubility product and matrix effects. Generally, the results suggested that the Athi river was only moderately polluted. Analy'sis of urine samples from those working in the cement factory had relatively higher concentrations for most of the metals than those not working in the factory (controls) with lead as the only exception.