Browsing by Author "Elisante, Eliapenda"

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Assessment of sources and transformation of nitrate in groundwater on the slopes of Mount Meru, Tanzania
(Springer, 2016-01-25) Elisante, Eliapenda; Muzuka, Alfred N. N.
The stable isotope compositions of nitrogen-nitrate (15N-NO3) and oxygen-nitrate (18O-NO3), and concentration of nutrients (NO3- NH4+, NO2 -, PO4 3- ) for water samples collected from springs, shallow wells and boreholes during dry and wet seasons were used to investigate sources and biogeochemical transformation of NO3- in groundwater along the slopes of Mount Meru. About 80 % of all water sources had nitrate concentration higher than background concentration of 10 mg/l during both seasons, while NH4+ and NO2 - concentrations were very low probably due to nitrification. Concentrations of NO3- above 50 mg/l were observed in some water sources. Concentrations of PO43- in all groundwater sources were very low during the two seasons owing to dilution and adsorption. The δ15N-NO3- for boreholes waters averaged +11.6 ± 2.1 and +10.7 ± 2.1 0/00 during dry and wet seasons, respectively. Similarly, the δ18 O-NO3 - of bore-hole waters for the wet and dry season’s averaged +5.2 ± 1.3 and +4.6 ± 1.9 %, respectively. With regard to dug wells, the δ15 O-NO3 - of well water averaged +13.3 ± 2.5 and +12.5 ± 2.3 %0 during dry and wet seasons, respectively, while the δ18 O-NO3 m- for the wet and dry seasons averaged +7 ± 2.3 and +6.4 ± 2.1 %, respectively. The δ15 O-NO3 -, for +11.2 ± 2.2 % during dry season and +11.7 ± 3.5 %0 during wet season whereas the δ18 O-NO3 - for the wet and dry seasons averaged +7.3 ± 3.6 and ?5.9 ± 2.6 %0, respectively. The isotopic data suggested that the source of NO3 - in the water sources are dominated by sewage and/or animal manure and to less extent, soil organic N. Few samples collected in close proximity of manure heaps and sanitary facilities had d15N values between 16 and 20 % suggesting occurrence of denitrification.
Occurrence of nitrate in Tanzanian groundwater aquifers: A review
(Springer Open, 2015-03-06) Elisante, Eliapenda; Muzuka, Alfred N. N.
More than 25 % of Tanzanian depends on groundwater as the main source of water for drinking, irrigation and industrial activities. The current trend of land use may lead to groundwater contamination and thus increasing risks associated with the usage of contaminated water. Nitrate is one of the contaminants resulting largely from anthropogenic activities that may find its way to the aquifers and thus threatening the quality of groundwater. Elevated levels of nitrate in groundwater may lead to human health and environmental problems. The current trend of land use in Tanzania associated with high population growth, poor sanitation facilities and fertilizer usage may lead to nitrate contamination of groundwater. This paper therefore aimed at providing an overview of to what extent human activities have altered the concentration of nitrate in groundwater aquifers in Tanzania. The concentration of nitrate in Tanzanian groundwater is variable with highest values observable in Dar es Salaam (up to 477.6 mg/l), Dodoma (up to 441.1 mg/l), Tanga (above 100 mg/l) and Manyara (180 mg/l). Such high values can be attributed to various human activities including onsite sanitation in urban centres and agricultural activities in rural areas. Furthermore, there are some signs of increasing concentration of nitrate in groundwater with time in some areas in response to increased human activities. However, reports on levels and trends of nitrate in groundwater in many regions of the country are lacking. For Tanzania to appropriately address the issue of groundwater contamination, a deliberate move to determine nitrate concentration in groundwater is required, as well as protection of recharge basins and improvement of onsite sanitation systems.
Origin and mechanisms of high salinity in Hombolo Dam and groundwater in Dodoma municipality Tanzania, revealed
(Springer Nature Switzerland AG., 2017-05-12) Shemsanga, Ceven; Muzuka, Afred; Martz, Lawrence; Komakech, Hans; Elisante, Eliapenda; Kisaka, Marry; Ntuza, Cosmas
The Hombolo dam (HD), in central Tanzania, is a shallow reservoir characterized by high salinity that limits its use for human activities. The origin of the salinity, mechanisms of reaching and concentrating in the dam remain unclear. These were assessed using hydrogeochemical facies, water type evolutions and mapping. The source of HD salinity was identified to be shallow groundwater (SG) and runoff from a seasonal floodplain with NaCl-rich lithological materails, along Little Kinyasungwe River that feeds the dam. The NaCl-rich lithological units, about 5–7 km upstream of the dam, were highly concentrated with NaCl to the extent that the local community was commercially separating table salt from them. The physicochemical parameters from these NaCl-rich lithological materials were well represented in HD and nearby groundwater sources, which suggests active water interactions. Water type evolution and surface hydrology assessments clearly showed that SG in the salty-floodplain was influenced by evaporation (ET) and was periodically carried to the HD. Clearly; HD water had high chemical similarity with the nearby SG. This agrees with previous studies that HD is partly fed by the local aquifer. However, this is the first attempt at mapping its physical origin. The origin of HD salinity was further supported by the spatial distribution of electrical conductivity (EC), where very high EC (up to 21,230 μScm−1) was recorded in SG within the NaCl-rich lithological unit while water sources far away from the NaCl-rich materials had much lower EC values. Thus, the study disagrees with previous conclusions that HD salinity was sorely due to high dam surface ET but is primarily due to geological reasons. Comparisons of HD with a nearby Matumbulu dam (MD), another earthen dam in climatologically similar settings, reveals that MD water was less saline/mineralised. This further shows that HD high salinity is most likely a geologic phenomenon, but local climatic factors, namely high ET, decreasing rainfall and warming trends are likely to have concentrated the salts further. Although HD is widely/ideally used for grape vine irrigation, it was clearly revealed that its prolonged usage would potentially affect the soil and grape productivity due to high salinity.