Undergraduate Research Projects Collection

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    Occurrence and potential health risks of indicator polychlorinated biphenyls in selected marine fish species: a case study of Dar es salaam
    (Sokoine University of Agriculture, 2023-03) Gabriel, Gabriel Jacob
    Polychlorinated biphenyls (PCBs) are industrial chemicals in a group of persistent organic pollutants (POPs) that are ubiquitous in environments including water bodies. Ocean sediments are one of the major reservoirs of PCBs, contaminated through runoff water, atmospheric transfer, and sewer discharge of industrial and municipal wastes, risking contaminating aquatic organisms. Fish are vulnerable to contamination because PCBs are highly lipophilic and can easily be absorbed and stored in fish fatty tissues. However, there are limited studies on the marine fish contamination status in Tanzania's coastal waters. The overall objective of the present study overall objective was to assess the occurrence and levels of indicator PCBs in selected species of marine fish in Dar es Salaam, and the specific objectives were to determine indicator PCBs levels in mackerel fish (Rastrelliger kanagurta) and rabbitfish (Siganus sutor) and to assess the dietary exposure and health risks of PCBs to artisanal fishermen and fish vendors. Fish samples were randomly collected from fishermen and fish vendors at Kivukoni Ferry fish market where a total of 60 fresh fish samples were collected from two different species, Rastrelliger kanagurta, and Siganus sutor, chosen based on the prior conducted food consumption survey. A food frequency survey was conducted among fishermen and fish vendors to assess the fish consumption habit of the respondents. PCBs extraction and sample matrix clean-up were done using the QuEChERS method and quantification analysis of PCBs was done using a Gas Chromatography tandem Mass Spectrometer (GC-MS/MS) at the Government Chemist Laboratory Authority (GCLA) laboratories. Results showed the presence of indicator PCBs in both fish species, with 73.3% of R. kanagurta samples and 20% of S.sutor samples showing PCBs contamination. The levels of the six indicator PCBs were relatively low in both fish species with the highest mean concentration (∑6PCBs), 3.71 ngg-1 w/w observed in R. kanagurta. The individual mean levels of detected indicator PCBs ranged from
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    Pathways for increasing agricultural water productivity
    (2007-01-03) Molden, David; Oweis, Theib Y; Pasquale, Steduto; Kijne, Jacob W; Hanjra, Munir A; Bindraban, Prem S; Bouman, Bas AM; Mahoo, Henry F; Silva, Paula; Upadhyaya, Ashutosh
    Water productivity is defined as the ratio of the net benefits from crop, forestry, fishery, livestock, and mixed agricultural systems to the amount of water required to produce those benefits. In its broadest sense it reflects the objectives of producing more food, income, livelihoods, and ecological benefits at less social and environmental cost per unit of water used, where water use means either water delivered to a use or depleted by a use. Put simply, it means growing more food or gaining more benefits with less water. Physical water productivity is defined as the ratio of the mass of agricultural output to the amount of water used, and economic productivity is defined as the value derived per unit of water used. Water productivity is also sometimes measured specifically for crops (crop water productivity) and livestock (livestock water productivity). To feed a growing and wealthier population with more diversified diets will require more water for agriculture on an average annual basis [well established]. Evapotranspiration from agricultural land is estimated at 7,130 cubic kilometers and without increases in water productivity could increase by 60%–90% by 2050 (see chapter 3 on scenarios). Agricultural water withdrawals from natural systems are estimated at 2,664 cubic kilometers, or about 70% of water withdrawn for human purposes. Additional water for agriculture will strain terrestrial and aquatic ecosystems and intensify competition for water resources. Improving physical water productivity in agriculture reduces the need for additional water and land in irrigated and rainfed systems and is thus a critical response to increasing water scarcity, including …