Anthropogenic and seasonal influence on the sediment-water fluxes for selected metals at Lake Naivasha, Kenya.
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Date
2008
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Lake Naivasha is a fresh water lake, situated in the Eastern Rift Valley of Kenya (00 45 S' and 360 20 E). The lake has no surface outlet and is perceived to be under anthropogenic stress. The lake being situated at the basin of the rift valley bares the burden of acting as a receptacle of waste from the town and the surrounding horticultural industry. To investigate the level of pollution due to bioavailable metals, benthic fluxes of selected metals were determined at sites near suspected pollution input sources. In situ benthic flux experiments were conducted at two sites, near the municipal outflow and at the papyrus field near the horticultural farms. Sediment samples from the exposed riparian land were collected during the dry season after the Lake had resided and selected metals fluxes determined in the laboratory under simulated conditions. Al in situ benthic flux at station SS (near the sewage input) was quite high it averaged 7 mmoles m2 h-I and was influenced significantly and positively by pH r=0.89. While Al in situ benthic flux at station SH (located in the papyrus field near horticultural farms) was I mmoles m-2 h-I. Copper Manganese and zinc in situ benthic fluxes were predominantly positive at station SS, however this was not the case at station SH (at papyrus field). The papyrus field at station SH plays an important role in the buffering of the lake in reference to the selected metals investigated, due to the precipitation of redox sensitive metals. Among the metals, analyzed manganese was mobilized the most during the rainy season, after the immediate flooding of the exposed riparian land.Pages
30pp.Publisher or University
Kenya Marine and Fisheries Research InstituteCollections