Browsing by Author "Lema, Meserecordias W."

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    Assessment of groundwater vulnerability zones using GIS-based DRASTIC model: A case of Makutupora basin, Dodoma-Tanzania
    (Indian Journals.com, 2016) Kisaka, Mary J.; Lema, Meserecordias W.
    This study was conducted in the Makutupora basin to evaluate the vulnerability of groundwater to contamination using DRASTIC method in a GIS (Geographical Information System) environment. ILWIS 3.0 (Integrated Land and Water Information System) and Arc view 3.2a GIS software were also used to find water vulnerable zones in the aquifers. Estimation of DRASTIC Index involves multiplying each parameter weight by its rating corresponding to its study area and summing the total. A groundwater pollution potential map was prepared and the DRASTIC Index (DI) of the area was calculated. The values for the DRASTIC index were classified into five classes: extremely low, low, moderate, high and extremely high. From this study, it was found that about 30% of the study area is occupied by high to extreme vulnerability, 20% is occupied by moderate vulnerability and 50% is occupied by the low to extremely low vulnerability. Areas with high to extreme vulnerability were due to fractures associated with aquifer, high recharge potential, shallow water table as well as agriculture activities. The vulnerability map produced could be useful for planners and decision makers for initiating groundwater quality development in their specific areas.
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    Assessment of soil pollution (heavy metal) from small scale gold mining activities: A case of Nyarugusu gold mines, Geita – Tanzania
    (Open Science, 2017) Lema, Meserecordias W.; Mseli, Zaina H.
    This research study investigated the concentrations of some heavy metals (Hg, Pb, Cu and Zn) in soil samples collected from Nyarugusu Gold Mines (located in Geita Region, Tanzania) using Atomic Absorption Spectroscopy (AAS). The results obtained showed that average concentration for Hg (25.45 mg/kg) was higher than the tolerable limits recommended by the United States Environmental Protection Agency (US-EPA). The average concentrations for Pb (10.14 mg/kg), Cu (19.75 mg/kg) and Zn (17.34 mg/kg) were found to be lower that tolerable limits, as prescribed by US-EPA. The high concentration of Hg measured at Nyarugusu site indicated existence of high health risks to plants animals and (especially humans). pH values for the soil samples were between 6.0 and 6.92 which is also dangerous for the availability of metallic minerals for plants consumption.
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    Sorption characteristics of hexavalent chromium in the soil based on batch experiment and their implications to the environment
    (Scientific Research Publishing, 2017) Lema, Meserecordias W.; Kwikima, Muhajir M.
    The objective of this experimental study was to determine the kinetics and equilibrium sorption of Cr (VI) in soils collected from Hengshui City of Hebei Province, China, based on batch experiments. The main concentration for this paper is on the effect of soil pH, solute concentration and ionic strength as the variable factors in the sorption of Cr (VI) in soils and the assessment of their implications to the environment. Atomic Absorption Spectrophotometer (AAS) was used for Cr (III) analysis; UV-VIS Spectrophotometer for quantification of Cr (VI) in soil samples and determination of electrical conductivity and temperature of the soil samples; and Automatic Laser Particle Size Analyzer LS230 for the determination of soil physical characteristics. Results from this study show that adsorption and reduction are major reactions accounting for removal of Cr (VI) from soil solution. It is concluded that chemical reactions such as reduction, strongly influence Cr (VI) mobility in soil. Adsorption kinetics experiments indicated that Cr (VI) removal from soil solution increases with increasing solute concentration, with decreasing pH and with decreasing ionic strength. Adsorption reactions reached equilibrium within 12 hours in batch reactors. Increasing background electrolyte concentration (KCI) decreases Cr (VI) adsorption on soil. The Cr (VI) adsorption isotherm for this soils conforms well to the Langmuir isotherm at constant pH. Two Cr (VI) adsorption parameters: the maximum sorption capacity (Qo) and Langmuir adsorption constant (KL), were determined as 1.0135 × 10−4 mol/g and 0.0622 mg/L, respectively. The reduction of Cr (VI) into less toxic Cr (III), means reduction of significant environmental problems. Finally, this study advises relevant environmental governing authorities to observe periodic monitoring of the status of Cr (VI) in soils.