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

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.

HUMAN EXPOSURE TO BACKGROUND RADIATION IN ORTUM, KENYA.

The activity concentration of radionuclides 238U, 232Th and 40K in soil and the absorbed dose rate (ADRA) at 1 m above the ground in Ortum was determined. The activity concentration in soils ranged from 33 to 85, 20 to 67 and 148-1019 Bq kg-1, respectively with an average of 40 ± 1.43, 56 ± 1.46 and 425 ± 19.24 Bq kg-1, respectively. The activity concentration of 232Th and 238U was found to reduce with increasing depth while that of 40K increased with increasing depth. The average activity concentration in soil was higher than the world average values. The average ADRA in air at 1 m above the ground was found to be 112 ± 29.6 nGy h-1. The soil and rocks in Ortum are recommended for use because the activity concentration of the terrestrial radionuclides is lower than the recommended threshold values.

Estimation of annual effective dose and radiation hazards due to natural radionuclides in Mount Homa, southwestern Kenya.

The radiological hazard of naturally occurring radioactive material in Mount Homa in southwestern Kenya was investigated after 210 point measurements and 44 samples were analysed. In situ measured average outdoor absorbed dose rate in air using survey meters was found to vary from 154.8 to 2280.6 nGy h(-1). The mean (range) values of radioactive concentrations measured using an HpGe detection system for (40)K, (226)Ra and (232)Th were 915 ± 3 (64-3017), 195 ± 8 (17-1447) and 409 ± 4 (23-1369) Bq kg(-1), respectively. The calculated range of the annual effective dose for a person living in Homa Mountain area varied from 28.6 to 1681.2, with a mean of 470.4 µSv. All calculated average radiological indices, namely Radium equivalent, Representative level, Gamma activity, External and Internal hazard, were higher than the limits set by various national and international bodies. These results imply that Mount Homa region is a high background radiation area.

An investigation of the repeatability of calibration factors in gamma-ray spectrometry of geological materials.

A NaI(Tl)-based gamma spectrometer for the analysis of geological materials was calibrated using the IAEA reference materials RGU-1, RGTH-1 and RGK-1. To simulate typical geological samples, two additional standards were prepared from aliquots of the three reference materials. The reproducibility of the instrument calibration factors (CFs) was tested by repeated measurements of the pure IAEA reference materials and the mixed samples in a reproducible counting geometry. The results were analysed using a two-way classification analysis of variance; it was found that the variance in the CFs is significantly higher between standards than it is between measurements. Allowance should be made for this when estimating uncertainties in measurements with the NaI(Tl) spectrometers.

Measurement of 222Rn concentration in Kenyan groundwater.

Groundwater samples from different parts of Kenya have been analyzed for their 222Rn concentrations. Samples were drawn from municipal supplies, springs, wells and bore holes in different geological terrains. In the analysis, conventional liquid scintillation counting, using the Packard protocol for measuring radon in water, was employed. This is the first time these water sources are being tested for radioactivity. The preliminary results are presented, and they showed that 222Rn is the main contributor to the radioactivity in most portable waters in Kenya. 222Rn activity concentrations range from 0.8 +/- 0.5 to 371.7 +/- 33.5 Bq L(-1).