Environmental assessment of heavy metal pollutants in soils and water from Ortum, Kenya.

Abstract

Analysis of elemental concentration in soil and water was carried out in Ortum to ensure safe utilization of soil and water resources for agriculture, industrial, and household purposes. Elemental analysis of soil and water was done using the EDXRF spectrometer and the inductively coupled plasma - optical emission spectrometry (ICP-OES), respectively. A total of 59 soil samples from different locations and depth and 10 water samples were collected from Ortum using purposive sampling method. The results of the mean elemental composition of 13 elements Ni (ppm), Cu (ppm), Zn (ppm), Pb (ppm), K (%w), Ca (%w), Fe (%w), Ti (%w), Mn (ppm), Rb (ppm), Sr (ppm), Zr (ppm), and Nb (ppm) in soils were 58.11, 46.91, 73.49, 22.20, 3.83, 24.39, 1.72, 7.73, 1529.74, 60.98, 442.26, 410.63, and 29.36, respectively, and the mean of 19 elements Ni, Cu, Pb, Zn, Ag, Al, As, Ba, Ca, Cd, Co, Cr, Fe, K, Mg, Mn, Mo, Na, and Se in water samples in (mg/l) were 0.037, 0.0014, 0.0005, 0.0042, 0.0030, 0.021, 0.0080, 0.12, 73.81, 0.00023, 0.0036, 0.00276, 0.0040, 6.11, 38.18, 0.00023, 0.0032, 46.87, and 0.0026, respectively. The average elemental concentration in soils was within the world average range. The mean concentration of Cu, Zn, and Pb in soil reduced with increase in depth while that of Ni increased with increase in depth. The average metal pollution indices in soils, geoaccumulation index (Igeo) potential ecological risk index (Ei), and synthesized potential ecological risk index (Er) were evaluated and found to be - 0.40, 4.92, and 19.69, respectively. According to the classification index, the results show that the soil in Ortum is moderately polluted, and the risk associated with the measured elemental concentration of Ni, Zn, Cu, and Pb in the soils is low. The elemental concentrations in water samples was lower than the recommended permissible limits except for Calcium (Ca) in borehole water with an average of 90.80 mg/l against the permissible levels of 75 mg/l (WHO, 2011). The pH for water samples was found to range from 6.60 to 7.71 with an average of 7.07 which is within the acceptable range of pH 6.5 to pH 8.5 as recommended by WHO, 2011. The study found out that elemental concentration in soil and water samples from Ortum were withing the world average values and that the soil and water in Ortum is safe for use in agriculture and domestic purposes.