A Numeric Modelling of Heavy Metals in Riverine Systems in Eldoret, Uasin Gishu County, Kenya

Heavy metals are gradually being added into water resources due to the rise in Municipal, industrial and agricultural activities. The fate of heavy metals being in water systems is mainly controlled by transport processes. Transportation of heavy metals by rivers can be both as metal in solution and adsorbed to suspended solids. A one-dimension environmental model has been developed in this work to simulate the transport of heavy metals discharged into a riverine system. The model has been developed by solving a mass transport equation. The governing equation describing the mathematical model is discretized implicitly by the integral finite difference method (IFDM). Heavy metal samples were collected along River Sosiani as it passes through Eldoret town. The concentration levels of copper, zinc and lead metals were analysed. The maximum values obtained for copper, zinc and lead were 0.35 mg/l, 0.48 mg/l and 0.23 mg/l respectively. The World Health Organisation (WHO)standards for drinking water are 0.2 mg/l, 0.05 mg/l and 0.5 mg/l for copper and lead and zinc respectively. The concentration values for copper and zinc were above WHO standards. The model developed in this study was validated for spatial variation of heavy metal concentration where field parameters like flow rate and dispersion coefficient were varied. The model also considered multiple sources of pollutants. There was close agreement between the measured and the simulated values. The results obtained in this study show that the model demonstrated good capabilities for describing spatial characteristics of heavy metals in riverine systems. It can be concluded that by using mass balance model it is possible to simulate heavy metal transport in surface waters for risk assessment purposes and is shown to be a useful management tool in monitoring water quality in River Sosiani

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