Browsing by Author "Vuai, S. A. H."
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Item Characterization of MSW and related waste-derived compost in Zanzibar municipality(SAGE, 2010) Vuai, S. A. H.The spread of municipal solid waste (MSW) in Zanzibar municipality has been associated with environmental pollution, unpleasant city conditions, contamination of water sources and coastal areas together with harbouring of malaria vectors. The contamination has a close relationship with eruption of diarrhoea, cholera and typhoid which claim the lives of the residents. Most of the wastes are of domestic and market origin and have the potential for compost production. This study examined the possibility of composting MSW from Zanzibar municipality as an alternative way of SW management and assessed the nutrient contents of the compost for application in agricultural production. Two major classes of SW were selected for the study: municipal solid waste and rice milling by-products. The samples were composted aerobically and anaerobically. The results showed that aerobic composting reduced about 60% of the waste volume. This volume reduction suggests that composting can be a promising SW management technique by reducing the large demand of space for landfilling. Municipal solid waste composted under anaerobic conditions produced compost with relatively higher concentrations of dissolved species than that produced under aerobic conditions. The trace metal contents were higher in MSW than in rice milling by-products. It was found that the unmanaged compost collected from the dumping site had low nutrient contents and was enriched with trace metals. Generally, physico-chemical characteristics, nutrients and trace metal levels suggest that Zanzibar municipal solid waste can produce high-quality compost for application to a wide range of soil types to improve their fertility, under proper management.Item Optimization of agar extraction from local seaweed species, Gracilaria salicornia in Tanzania(Wiley Online, 2019) Vuai, S. A. H.; Mpatani, F.This study aimed to develop agar extraction protocols for Gracilaria salicornia from Tanzania and investigate its physico‐chemical characteristics. A 33 factorial experimental design was used in the extraction of agar whereby three independent variables of NaOH concentration (10, 20 and 30% w/v), alkali pre‐treatment duration (0.5, 1 and 2 h) and extraction temperatures (115, 120 and 125°C) were used to determine the optimum conditions for production of high‐quality agar. Agar yield, gel strength, sulfate content, gelling and melting temperatures were evaluated as dependent variables. The optimal condition was observed at 30% NaOH concentration, 2 h alkali pre‐treatment duration and 120°C extraction temperature. The yield, gel strength, sulfate content, gelling and melting temperatures of the agar obtained under these conditions were 26.9 ± 0.7%, 510.3 ± 16.2 g cm−2, 0.29 ± 0.04%, 39.3°C and 88.4°C, respectively. These properties are very close to that of imported commercial agar. It was concluded that the local agar is capable of replacing imported agar for most general purposes. This offers a new possibility of using quality local agar in place of commercial agar.Item Prevalence and factors associated with designer cathinones and amphetamine use among Outpatients attending methadone clinic at Mwananyamala hospital Dar es salaam, Tanzania(Elsevier, 2023) Ripanda, A.S.; Srivastava, B. B. L.; Nyundo, A. A.; Miraji, H.; Vuai, S. A. H.Designer cathinone and amphetamines are synthetical analogues of stimulant phenethylamines, including ring-substituted cathinones that are claimed to have effects similar to those of cocaine, hence, intentionally or unintentionally used for recreation purposes and as a substitute. The information regarding designer cathinone and amphetamines use is publicly limited.Item Solute generation and CO2 consumption during silicate weathering under subtropical, humid climate, northern Okinawa Island, Japan(Elsevier, 2007) Vuai, S. A. H.; Tokuyama, A.The chemical characteristics of freshwaters draining the silicate rocks in the northern part of Okinawa Island were studied to understand solute generation processes, and to determine rates of chemical weathering and CO2 consumption. It was observed that the water chemistry is highly influenced by marine aerosols, contributing more than 60% of total solute. Significant positive correlations observed for chloride versus dissolved silica and chloride versus bicarbonate suggest a strong influence of evapotranspiration on the seasonality of solute concentration. It was also found that chemical weathering has been highly advanced in which the dominant kaolinite minerals are being gibbsitized. Carbonic acid was found to be the major chemical weathering agent, releasing greater than 80% of weathering-derived dissolved cations and silica while the remaining portion was attributed to weathering by sulfuric acid generated via oxidation of pyrite contained in the rocks. The flux of basic cations, weathering-derived silica and CO2 consumption were relatively high due to favourable climatic condition, topography and high rate of mechanical erosion. Silicate weathering rates for basic cations were estimated to be 6.7–9.7 ton km− 2 y− 1. Carbon dioxide consumed by silicate weathering was 334–471 kmol km− 2 y− 1 which was slightly higher than that consumed by carbonate weathering. In general, divalent cations (Mg and Ca) and bicarbonate alkalinity derived from carbonate dissolution were higher than those from silicate weathering. As a consequence, the evolution of chemical species in the freshwaters of northern area of Okinawa Island to a large extent could be explained by mixing of two components, characterized by waters with Na+ and Cl− as predominant species and waters enriched with Ca2+ and HCO3−.Item Trend of trace metals in precipitation around Okinawa Island, Japan(Elsevier, 2011) Vuai, S. A. H.; Tokuyama, A.Okinawa Island is located between mainland Japan to the northeast, Taiwan to the southwest and China to the west. In recent years, precipitation with relatively low pH has been observed in the island during winter seasons. This study was conducted to evaluate the potential sources and factors affecting distribution of trace metals in the atmosphere around the northern area of Okinawa Island. The results showed that the trace metal contamination was low comparable to rural areas of less industrialized countries. The annual average depositions were 6.0, 5.2, 4.4, 2.7 and 20.4 kg km− 2 y− 1 for Al, Fe, Mn, Cu, and Zn, respectively. The metals in the precipitation were mainly derived from the dissolution of wind-blown soil particles. The distribution of trace metals across the island showed the influence of road traffic as a source and cause of atmospheric pollution. Aluminium and Fe were found to be high closer to the main road and decreased further away from the road, while Zn and Cu were strongly correlated with average mean pH of precipitation. The variation of concentrations in the island was attributed to the distance from the main road, average rain pH at a particular sampling location and wind speed and direction. A strong correlation between lithological elements (Al and Fe) and anthropogenic elements (Zn and Cu) indicates that they were carried by the same particles and experienced similar scavenging mechanism during dissolution process.