Radionuclide Content of Sands Used for Construction in Kakamega County, Kenya and Associated Indoor Radon Diffusion Fluxes

Studies have been carried out to determine the natural radioactivity in construction sand and their associated radiation hazard in the old gold mining belt of Kakamega County, Kenya. The radioactivity concentrations of 226Ra, 232Th and 40K were measured using a gamma ray spectrometer with a NaI(Tl) detector. The results of concentrations of naturally occurring radionuclides were as follows: 226Ra ranged from 36.79±8.89 to 185.21±5.89 Bqkg-1, 232Th ranged from 322.38±2.56 to 158.92±7.95 Bqkg-1and 40K ranged from 322.38±16.12 to 960.53±48.03 Bgkg-1. The radium equivalent activities and the radiation hazard index associated with the natural radionuclides were calculated. A computer program was developed and applied to estimate the diffused indoor radon concentration by solving a simple transport equation. The indoor radon was assumed to originate from the walls of a room constructed from sands rich in uranium minerals found in this region. Keywords: Radioactivity; Radium; Thorium; Potassium; Building sand; Indoor rado

Radionuclide Content of Sands Used For Construction in Kakamega County, Kenya and Associated Indoor Radon Diffusion Fluxes

Studies have been carried out to determine the natural radioactivity in construction sand and their associated radiation hazard in the old gold mining belt of Kakamega County, Kenya. The radioactivity concentrations of 226Ra, 232Th and 40K were measured using a gamma ray spectrometer with a NaI(Tl) detector. The results of concentrations of naturally occurring radionuclides were as follows: 226Ra ranged from 36.79±8.89 to 185.21±5.89 Bqkg-1, 232Th ranged from 322.38±2.56 to 158.92±7.95 Bqkg-1and 40K ranged from 322.38±16.12 to 960.53±48.03 Bgkg-1. The radium equivalent activities and the radiation hazard index associated with the natural radionuclides were calculated. A computer program was developed and applied to estimate the diffused indoor radon concentration by solving a simple transport equation. The indoor radon was assumed to originate from the walls of a room constructed from sands rich in uranium minerals found in this region. Keywords: Radioactivity, Radium, Thorium, Potassium, Building sand, indoor rado

An algorithm for simulation of a Chemical Transport Equation in an Aquifer

Dynamical systems can be predicted using mathematical models. These models are usually Partial Different Equations (PDEs). Examples include the wave equation, equations for diffusive processes, and the heat conduction equation. Numerical solution of such PDEs describing a given system and its implementation using a suitable computer code can lead to numerous predictions on the dynamical system both in space and time. In this paper, the contaminant / chemical equation and the groundwater flow equation are solved numerically using the Integrated Finite Difference Method (IFDM) and the algorithms generated are simulated using an object oriented code. Generic results generated represent important predications on the fate and transport processes of a chemical in an aquifer   Keywords: Simulation procedure, integrated finite difference method, contaminant equation, discretizatio

Gamma Ray Spectrometric Analysis of Sedimental Deposits at the Shores of Lake Nakuru, Kenya

The main objective of this study was to assess human exposure to natural sources (U-238, Th-232 and K-40) of radiation on the shores of Lake Nakuru, Kenya. Gamma ray spectrometry of soil samples was done using NaI(Tl). The results obtained showed average activity concentrations of 36.9±9.1, 43.5±3.8 and 708±33.2 in Bqkg-1 for 238U, 232Th and 40K respectively. A total dose rate of 71.97 nGyh-1, annual effective dose rate (outdoor) of 0.088 mSv and average hazard index of 0.410 were obtained. The average dose rate for the northern sector was found to be 96.22±5.39 nGy/h while the southern sector has 26.69±0.69 nGy/h showing enhanced pollution at the northern sector. The findings from this study showed that radiation hazard from terrestrial naturally occurring radionuclides is low and human radiation exposure is within safe levels. Spatial difference in the activity concentration between the northern and southern sectors of Lake Nakuru was observed. There is need to closely monitor the northern sector and the rivers discharging water there in order to establish the source of the elevated activity. Keywords: Radionuclides, NaI(Tl) ?-ray Spectrometer, Activity concentration, Dose rate, Lake Nakur

Fluoride adsorption onto an acid treated lateritic mineral from Kenya: Equilibrium studies

Adsorption of fluoride (F) ions from water using acid treated lateritic mineral (LM-1) from Kenya was studied by batch experiments. The effect of acid-treatment of adsorbent and change in temperature, mass of LM-1, pH and selected competing ions was evaluated. The adsorption process was strongly influenced by temperature, pH and adsorbent dosage. The percentage F removal increased the presence of the nitrate and the chlorate ions but decreased the presence of sulphates, chloride and phosphate ions. Adsorption isotherms were classified according to Giles’ classification and the adsorption data validated using Langmuir and Freundlich isotherms. The data correlated to both the Langmuir and Freundlich isotherms although the data fit to the Freundlich model was somehow better. This showed that F adsorption onto LM-1 followed a mixed adsorption mechanism in which physisorption reactions involving intra-particle diffusion of F into mesoporous sites in LM-1 became increasingly important at higher concentrations and temperatures whereas ion-exchange mechanism involving surface OH- appear to dominate at low surface coverage in more alkaline conditions. With maximum adsorption capacity of 10.5 mg/g, LM-1 could be used to remove F water.Key words: Equilibrium analysis, fluoride adsorption, Langmuir and Freundlich isotherms, Lateritic mineral adsorbent, low-cost adsorbents

Equilibrium Studies of Fluoride Adsorption onto a Ferric Poly 12mineral from Kenya

African countries along the Great Rift Valley are among areas of the world where excess fluoride in water sources is a major public health problem. In this work, the removal of fluoride (F) from water solutions using a ferric poly-mineral (FPM) from Kenya was therefore studied using batch adsorption experiments. The effect of change in solution pH, temperature, initial concentration of F, mass of FPM, contact time and presence of various competing ions on F adsorption onto FPM was evaluated. Adsorption isotherms were then applied to the adsorption data to characterize and establish the adsorption capacity of the mineral. The adsorption of F onto FPM was found to be a fast process and, at 1000 mg/L initial F concentration at pH 3.32 and 293 K and using 0.2 g/mL adsorbent dosage, over 90% F removal from solution could be achieved in 30 min. Based on Giles system of classification of adsorption isotherms, F adsorption isotherm conformed to L4 Langmuir-type isotherms. This indicated that FPM is composed of a heterogeneous surface consisting of sites which, during adsorption, filled-up with F ions in succession. The adsorption data also correlated to Langmuir and Freundlich models indicating that F adsorption onto FPM was a mixed process involving chemisorption onto surface sites followed by gradual intra-particle penetration of F into mesoporous structure of the mineral. High mean Langmuir adsorption capacity of 10.8 mg/g, indicate that the mineral could be of use as an inexpensive substrate for the removal of F from aqueous streams

Results of injection and tracer tests in Olkaria East Geothermal Field

This paper presents results of a six month Injection and Tracer test done in Olkaria East Geothermal Field The Injection tests show that commencement of injection prior to onset of large drawdown in the reservoir leads to greater sustenance of well production and can reduce well cycling which is a common feature of wells in Olkaria East Field. For cases where injection is started after some drawdown has occurred in the reservoir, injection while leading to improvement of well output can also lead to increase in well cycling which is a non desirable side effect. Tracer tests reveal slow rate of fluid migration (< 5 m/hr). However estimates of the cumulative tracer returns over the period of injection is at least 31% which is large and reveals the danger of late time thermal drawdown and possible loss of production. It is shown in the discussion that the two sets of results are consistent with a reservoir where high permeability occurs along contact surfaces which act as horizontal "fractures" while the formations between the "fractures" have low permeability. This type of fracture system will lead to channeled flow of injected fluid and therefore greater thermal depletion along the fractures while formations further from the fracture would still be at higher temperature. In an attempt to try and achieve a more uniform thermal depletion in the reservoir, it is proposed that continuous injection be done for short periods (~2 years) and this be followed by recovery periods of the nearly the same length of time before resumption of injection again

A study of relative permeability for steam-water flow in porous media

We report on continuing experimental and numerical efforts to obtain steam-water relative permeability functions and to assess effect of heat transfer and phase change. To achieve these, two sets of steady-state flow experiments were conducted: one with nitrogen and water and another with steam and water. During these experiments, a mixture of nitrogen-water (or steam-water) was injected into a Berea sandstone core. At the onset of steady state conditions, three-dimensional saturation distributions were obtained by using a high resolution X-ray computer tomography scanner. By identifying a length of the core over which a flat saturation profile exists and measuring the pressure gradient associated with this length, we calculated relative permeabilities for nitrogen-water flow experiments. The relative permeability relations obtained in this case were in good agreement with those reported by other investigators. Another attempt was also made to conduct a steam-water flow experiment under adiabatic conditions. This experiment was completed with partial success due to the difficulties encountered during the experiment. The results of this experiment showed that a flat saturation profile actually developed over a substantial length of the core even at a comparatively modest injection rate (6 grams per minute) with low steam quality (4% by mass). The completion of this set of experiments should yield steam-water relative permeability relations in the near future

Fluoride Adsorption onto Acid-Treated Diatomaceous Mineral from Kenya

International audienc

Human health risk assessment of heavy metal concentration in surface water of Sosian river, Eldoret town, Uasin-Gishu County Kenya

Heavy metal pollution in surface waters has become a major worldwide issue as people tend to settle where there is readily available source of water like a river. This research evaluates the causes, concentration and associated health risks of heavy metals in River Sosiani as it passes through the town of Eldoret. Seven water samples were collected and analysed for zinc (Zn), copper (Cu) and lead (Pb. The results disclosed that Pb concentrations were estimated to be in the range of 0.06 mg/l to 0.23 mg/l, higher than the permitted limit by WHO of 0.01 mg/l. Cu and Zn concentration levels were below the permissible limits. The chronic daily intake (CDI) indicated that total hazard quotient of non-cancer risk of Pb was above one and the total HI values for children were greatly elevated compared to those of adults in the studied area. This showed a high risk in exposure to Pb. Health human risk was assessed and the incremental life cancer risk (ILCR) values of Pb for children and adults in all sites were found to be negligible with values below 10−6. However, there is higher cancer and non-cancer risk for children than adults as far as lead metal is concerned. Therefore, measures should be taken in accordance with the standards to prevent potential risk of the river pollution. • Human activities make a significant contribution to heavy metal pollution to surface waters which is a threat to humans. • Water from Sosiani River is not safe for use domestically as far as lead metal levels are concerned. • The results of this study can be used by decision makers to develop measures which can improve the quality of water in the river catchment