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The distribution of diatoms and major elements in a regulated river system: a study of the Zambezi River in the Lake Kariba area
2001 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Dam wall constructions in regulated rivers can have profound effects on the composition of the dissolved and suspended phase, as well as diatom concentrations in rivers. The purpose of this undergraduate study was to evaluate if the Kariba Dam, located on the Zambezi River, in southern Africa, acts as a sink for nutrients and diatoms. To see if these mechanisms could be detected for the Kariba Dam, analyses of the element content of the dissolved and suspended phase and quantification of the amount of diatoms in the water column at locations upstream, within and downstream from the dam impoundment at Kariba have been made. Samples of the dissolved and suspended phase were collected at four locations along the Zambezi River and one sample was collected in the Kafue River just before its confluence with the Zambezi River. Samples for analysing the diatom concentration were collected at five locations along the Zambezi River and one sample was collected in the Kafue River. The concentration of diatom-frustules in the water was evaluated by adding a known amount of microspheres to the sample and then counting the diatoms under a microscope. The concentration of total suspended solids in the Lake Kariba decreases compared to upstream from the lake, the decrease is an effect of the regulation of the Zambezi River. This study shows that there is a decrease in the suspended element concentrations within the lake and downstream from the dam construction at Kariba, relatively upstream from the lake. Silica is a main component in diatom frustules. The average non-detrital Si per diatom valve was found to be 15 pmol/valve. The concentration of diatom valves within and downstream Lake Kariba is lower than upstream the lake. The concentration of dissolved Si decreased between the two sampling points within the lake, which is a possible indication of uptake of Si by diatoms, but in this case the decrease is very small and probably not significant. The concentration of suspended Si decreased between the two sampling points within Lake Kariba, probably due to sedimentation of silicate minerals.According to the results from the analyses made, it can not be concluded that there is a significant uptake of dissolved Si by diatoms in Lake Kariba.

Place, publisher, year, edition, pages
2001.
Keyword [en]
Technology, Diatoms, Zambezi River, Zambia, Zimbabwe, hydrogeochemistry, suspended particulate material, major elements
Keyword [sv]
Teknik
Identifiers
URN: urn:nbn:se:ltu:diva-57374ISRN: LTU-EX--01/044--SELocal ID: e0cfc483-5851-45df-abc2-c722273d903eOAI: oai:DiVA.org:ltu-57374DiVA: diva2:1030761
Subject / course
Student thesis, at least 30 credits
Educational program
Environmental Engineering, master's level
Examiners
Note
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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