Use of 210Pb and 137Cs radionuclides as simple method of estimating sedimentation rates on reservoir

This research article was published in Arab Journal of Nuclear Sciences and Applications, Volume 56, 2023.Reservoirs are important for flood control, production of hydroelectric power, fishing, water harvesting and storage. Climate is changing, population and anthropogenic activities are increasing which increase sedimentation rate to most of reservoirs reducing their capacity. With climate change in mind water are becoming scarce resources which need proper storage when available and suitable flood control in areas with unpredicted rainfall. Furthermore, energy demand is increasing with population growth suggesting a need of sustainable management of dams so as to control flood, produce more hydroelectric power and store water to use in dry season. Sedimentation is one of the factors influencing storage capacity of the reservoir. Understanding sedimentation rate, source of sediment and carryout proper management measures is one among of the important methods to preserve dams. 137Cs and 210Pb are important radionuclides for investigating sedimentation rate. The method has been used for more than two decades in developed countries with less use in developing countries. In this study a sediment core was sampled at the centre of Nyumba ya Mungu reservoir in Tanzania, the samples were then transported to China for processing and analysis. High-purity Germanium detector was used for analysis. The results showed that rate of sedimentation in the reservoir ranged from 0.21 to 0.65 cm/year with more sediment coming from Kikuletwa than Ruvu tributary. The range is comparable to most of reservoir in tropics of developing country. Proper utilization of this method can bring sustainable management of water, save communities from flood disaster and increase production of electricity

Assessment of variation in marginal productivity value of water in paddy farming systems in times of water stress

This research article was published in Water Journal, Volume 14, 2022.Global projections show that increases in agriculture water productivity (AWP) by 30 and 60% in rain-fed and irrigated agriculture, respectively, are required to ensure food security in the period 2000–2025. In sub-Saharan Africa, attempts to understand AWP has seen a lamping of input values which paints an unrealistic picture of AWP. We employed the residual imputation method to isolate the marginal productivity value of water in six paddy farming systems viz. the conventional transplant and flooding system (CTFS), the system of rice intensification (SRI), and the Kilombero Plantation Limited (KPL) mechanized system. Findings showed that AWP for rainfed CTFS is 0.39 kg/m3 or 0.003 US$/m3 , irrigated CTFS (0.30 kg/m3 or 0.002 US$/m3 ), rainfed SRI (0.68 kg/m3 or 0.08 US$/m3 ), irrigated SRI (0.52 kg/m3 or 0.06 US$/m3 ), rainfed KPL (0.33 kg/m3 or 0.05 US$/m3 ), and irrigated KPL (0.68 kg/m3 or 0.11 US$/m3 ). This shows that rainfed systems have good AWP, especially physical ones. We recommend a rollout of rainfed SRI to secure local food security and downstream ecosystem services. In addition, groupings of farmers will assist in optimizing resources, stabilizing markets, and prices for the better economic value of water (US$/m3 ). Adoption of SRI will require intensive demonstration that needs public financing. In addition, revamping the KPL off-taker arrangement with small-holder farmers could also be a good PPP anchor

Integrated constructed wetlands treating industrial wastewater from seed production

This research article published by IWA Publishing, 2021The performance of an integrated wastewater treatment system composed of horizontal subsurface flow constructed wetland (HSSFCW), floating constructed wetland (FCW), and anaerobic baffled reactor (ABR) was studied for pollutant removal from seed production wastewater. Cyperus alternifolius (Umbrella Papyrus) plants were used in the HSSFCW, and Vetiveria zizanioides (Vetiver grass) in the FCW. The ABR was fed with 25 m3/d wastewater from its equalization tank. The average raw wastewater organic loading rate was 0.208 kg-COD/d. Grab wastewater samples were collected twice weekly for three months from each unit's inlet and outlet. The system's performance in removing biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), turbidity, nitrate, phosphate, and ammonium was studied. The average removal efficiencies obtained were 95.5% BOD5, 94.6% COD, 86.2% TSS, 76.6% turbidity, 82.4% nitrate, 76% phosphate, and 32.9% ammonium. The results show that integrating ABR, HSSFCW, and FCW improves pollutant removal from seed production wastewater, and the treated water can be used for agricultural purposes

Distribution and yield of trace metals from the foot of Mount Kilimanjaro to the coastal of Indian Ocean: impacts of natural and anthropogenic factors

This research articles was published in Journals Geochemistry 2022Cases of water related diseases due to metal pollution are increasing over the global. The condition is serious to most of developing countries as a results of industrialization and population growth. Dissolved and particulate trace elements influence drinking water, aquatic ecosystem health and climate change. Mt. Kilimanjaro is one of the sources of water and icon in Africa but miss studies on dissolved and particulate metals. Therefore, this study was conducted to investigate geochemistry, distribution and yield of dissolved and particulate metals from Mt. Kilimanjaro to Indian Ocean. Surface water was sampled in rainy season and analyzed by high resolution inductively coupled plasma mass spectrometry in State Key Laboratory of Estuaries and Coastal Research. Health assessment revealed that level of Aluminium, iron, vanadium and Manganese in some stations were above recommended level, that can pose health impact to human and aquatic ecosystem. Correlation of Cobalt, Copper, Manganese and Vanadium with dissolved silicate, sulphate, calcium and dissolved organic carbon indicates that these elements were predominantly found in silicate, sulphide, carbonate and organic bounds. Positive relation between magnetic susceptibility with Copper and zinc reflects that magnetic susceptibility can be used as indicator of Copper and Zinc pollution. Rock weathering and anthropogenic activities were main sources of metals whereas redox reactions, pH, temperature and dissolved organic carbon were some of biogeochemical factors influencing level of metals. The basin transported more elements in particulate than dissolved form. Yield from Pangani River to Indian Ocean was lower than most of other rivers in East Africa

Hydrogeochemical similarities and groundwater-surface water interactions for the karst hydrological system of northwest Rwanda

This research article was published in Arabian Journal of Geosciences, Volume 16, 2023.The groundwater of karst environments is vulnerable to pollution due to its heterogeneous nature and can be completely depleted due to its strong connection to surface water when predominantly driven by natural and anthropogenic factors. This particular landscape is the main source of drinking water in different parts of the world. Karst Hydrological of Rwanda hosts surface and groundwater resources. Moreover, groundwater is the main source of domestic water use in that area. The surface water is threatened by drying of crater lakes, changes of other lakes, and obstruction of sinkholes swallowing water from streams and runoff. Those problems may have direct and long-term impacts on groundwater recharge. The information on the hydrogeological characteristics of surface and groundwater, groundwater-surface water interaction, was limited. This study investigated the hydrogeochemical characteristics, similarities, and interactions of surface groundwater. To understand long-term impacts of surface water challenges on groundwater when are connected, statistical analyses and Piper diagram were used to achieve the objectives. The results showed a strong correlation among spring waters, reflecting similarity in the water origins. The Piper diagram classified the water as bicarbonate water (HCO−3 , Ca2+, Mg2+). The analysis of variance between surface water and groundwater did not show significant differences at the 0.05 level, which explains a relationship. The results showed a strong similarity and interaction between surface and groundwater. The findings of this study are important for water managers in consideration of future management since current problems on surface water may affect groundwater and community depending on that resource

Removal of arsenic in a sand filter coupled with zero valent iron

This research article was published in Hydro-research Journal, Volume 6, 2023.Arsenic (As) in wastewater has negative effects on the environment and human health, hence As containing wastes must be handled properly. Given the accessibility of metallic iron, studies investigating into the potential application of zerovalent iron in the removal of arsenic are promising. In this study, the performance of sand filter blended with several kinds of zero valent iron (Fe0), such as iron wool, iron fillings, and iron nails, were compared. These materials were combined in a sand filter column, and the efficiency was calculated using the As concentrations in the influent and effluent samples. Experiments were carried out in order to compare performance as a function of Fe0 dose and contact time. The outcome of this investigation showed that sand filter containing iron wool had a better removal efficiency of arsenic removal than iron filings and iron nails. The results in all columns showed that as dosage was increased, removal efficiency of arsenic increased significantly. In case of contact time the results revealed that arsenic can effectively be removed from water in the first 48 h. The early adsorption response is quick in all columns, but get slower as time goes on. The highest removal efficiency was 99.6% and the lowest removal efficiency was 82.7%

Land Use and Environmental Gradients Influence on Riparian Woody Plant Diversity and Structure in Lake Manyara Watershed Ecosystem, Tanzania

This research article was published in Open Journal of Ecology, Volume 13, 2023.Riparian vegetations are important in supporting ecological connectivity between aquatic and terrestrial ecosystems. The structure and species composition of riparian woody plants have been subjected to multiple forces with varying degree of influences. This study examined the influence of land use and environmental gradient to the structure and composition of the riparian woody plants in northern Tanzania. A total of 270 plots were surveyed for woody plant species in the riparian ecosystems and later analysed to determine the influence of land use categories (homegarden, crop field, woodlot, open canopy forest, and closed canopy forest) and environmental variables (temperature, precipitation, elevation and slope) to the species richness, abundance, and stand parameters. Basal area was higher in woodlots, homegardens and crop fields than in the open and closed canopy forests; and as expected the reverse was true for the number of stocking density. Correlation among stand parameters with environmental variables varied significantly. Species richness and species abundance were negatively correlated to precipitation, temperature and elevation, while stocking density and basal area were positively correlated to precipitation. The study recommends continual retentions of trees on farm, further promoting of agroforestry interventions and sustainable utilization of woody plants in open and close canopy forests

Household factors associated with access to insecticide-treated nets and house modification in Bagamoyo and Ulanga districts, Tanzania.

BACKGROUND: Insecticide-treated nets (ITNs) and house modifications are proven vector control tools, yet in most regions, full coverage has not been achieved. This study investigates household factors associated with access to ITNs and house modification in Tanzania. METHODS: Baseline cross-sectional survey data from previous studies on spatial repellants and indoor residual spray evaluation was analysed from 6757 households in Bagamoyo (60 km north of Dar es Salaam) and 1241 households in Ulanga (a remote rural area in southeast Tanzania), respectively. Regression models were used to estimate the associations between the outcomes: population access to ITNs, access to ITN per sleeping spaces, window screens and closed eaves, and the covariates household size, age, gender, pregnancy, education, house size, house modification (window screens and closed eaves) and wealth. RESULTS: Population access to ITNs (households with one ITN per two people that stayed in the house the previous night of the survey) was 69% (n = 4663) and access to ITNs per sleeping spaces (households with enough ITNs to cover all sleeping spaces used the previous night of the survey) was 45% (n = 3010) in Bagamoyo, 3 years after the last mass campaign. These findings are both lower than the least 80% coverage target of the Tanzania National Malaria Strategic Plan (Tanzania NMSP). In Ulanga, population access to ITNs was 92% (n = 1143) and ITNs per sleeping spaces was 88% (n = 1093), 1 year after the last Universal Coverage Campaign (UCC). Increased household size was significantly associated with lower access to ITNs even shortly after UCC. House modification was common in both areas but influenced by wealth. In Bagamoyo, screened windows were more common than closed eaves (65% vs 13%), whereas in Ulanga more houses had closed eaves than window screens (55% vs 12%). CONCLUSION: Population access to ITNs was substantially lower than the targets of the Tanzania NMSP after 3 years and lower among larger households after 1 year following ITN campaign. House modification was common in both areas, associated with wealth. Improved access to ITNs and window screens through subsidies and Behaviour Change Communication (BCC) strategies, especially among large and poor households and those headed by people with a low level of education, could maximize the uptake of a combination of these two interventions

Distribution of organic carbon: possible causes and impacts in the Pangani River Basin ecosystem, Tanzania

This research article was published in Environmental Chemistry Journal, Volume15, 2018.There is limited information on organic carbon in African rivers, especially from the eastern side. Here, we report distribution and impacts of total suspended matter (TSM), and dissolved and particulate organic carbon (DOC & POC) in the Pangani River Basin (PRB) ecosystem together with their fluxes to the Indian Ocean. δ13C was also used to trace sources of carbon in the basin. Results showed that the basin is supplied with carbon from allochthonous sources dominated by C3 plants, with higher levels of TSM and DOC in the wet season than in the dry season. Several factors, including altitude, temperature, rainfall, lithology and anthropogenic activities, have a significant influence on the seasonal and spatial distribution of organic carbon in the basin. High discharge in the wet season mobilised terrestrial organic carbon to elevate concentrations of DOC, POC and TSM. Mean concentrations of DOC, dissolved inorganic carbon (DIC), POC and TSM in PRB were in ranges comparable to that in other tropical rivers but their fluxes were lower than in most tropical rivers around the world. Diverting water from the river for irrigation and hydroelectric power production was one of the factors that reduced the flux of carbon. Observed hypoxic conditions in the reservoir indicates that the quality of water for human and aquatic ecosystem health is possibly threatened by a high level of organic carbon; furthermore, the trends of increasing population, deforestation, temperature and rainfall will likely increase the concentration of organic carbon in the future. Better management of waste, afforestation and reforestation are recommended to restore degraded natural forest, so as to reduce uptake of organic carbon from the terrestrial environment

Seasonal water chemistry variability in the Pangani River basin, Tanzania

Research Article published by SpringerThe stable isotopes of δ18O, δ2H, and 87Sr/86Sr and dissolved major ions were used to assess spatial and seasonal water chemistry variability, chemical weathering, and hydrological cycle in the Pangani River Basin (PRB), Tanzania. Water in PRB was NaHCO3 type dominated by carbonate weathering with moderate total dissolved solids. Major ions varied greatly, increasing from upstream to downstream. In some stations, content of fluoride and sodium was higher than the recommended drinking water standards. Natural and anthropogenic factors contributed to the lowering rate of chemical weathering; the rate was lower than most of tropical rivers. The rate of weathering was higher in Precambrian than volcanic rocks. 87Sr/86Sr was lower than global average whereas concentration of strontium was higher than global average with mean annual flux of 0.13 × 106 mol year−1. Evaporation and altitude effects have caused enrichment of δ18O and δ2H in dry season and downstream of the river. Higher d-excess value than global average suggests that most of the stations were supplied by recycled moisture. Rainfall and groundwater were the major sources of surface flowing water in PRB; nevertheless, glacier from Mt. Kilimanjaro has insignificant contribution to the surface water.We recommend measures to be taken to reduce the level of fluoride and sodium before domestic use