Browsing by Author "Ibembe, John D."

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    Influence of land use activities on spatial and temporal variation of nutrient deposition in Mwanza region: implication to the atmospheric loading to the Lake Victoria
    (Scientific Research, 2013) Vuai, Said A. H.; Ibembe, John D.; Mungai, Nancy W.
    Increase in population growth and the associated activities have increased the nutrient input to the Lake Victoria through atmosphere and river discharge. Atmospheric input of nutrient is believed to exceed that of river discharge due to relatively higher contribution of water mass to the Lake from atmosphere. However, precipitation characteristics with respect to nutrients have not been well studied to allow qualification and quantification of atmospheric contribution to the Lake Victoria. This study was conducted to investigate influence of land use activities on spatial and temporal variation of nutrient inputs from atmosphere and to estimate atmospheric loading to the Lake Victoria. The results re- vealed that there is significant spatial and temporal variation of nutrient deposition in the study area. High concentra- tions of nutrients were observed during short rains starting from September to December. This was attributed to dissolu- tion of nutrients from soil particals and ash residues due to biomass burning accumulated in the atmosphere during dry season of June to August. Spatial variation of nutrients reflects land use activities. Urban and peri-urban areas showed very high concentration of nitrate nitrogen due to industrial and vehicle emission while rural area showed high concen- tration of phosphorous species and reduced forms of nitrogen species reflecting agricultural activities and animal keep- ing. Generally, nutrient deposition load was higher in rural area compared to urban with respective values of 15.5 and 13.9 kg·ha−1·y−1 for total nitrogen and 6.1 and 2.8 kg·ha−1·y−1 for total phosphorous. These results suggest that in order to realize significant reduction of nutrient input to the Lake Victoria, measures should be taken to control agricultural activities through proper land use planning. The measure may be directed to reduce biomass burning, emission from industries and vehicle as well as animal residue.
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    Spatial variation of nutrients in Sondu-miriu and Simiyu-duma rivers: Implication on sources and factors influencing their transportation into the Lake Victoria
    (OMICS Publishing Group, 2012) Ibembe, John D.; Mungai, Nancy; Vuai, Said A. H.
    Lake Victoria basin has been under growing pressure from both natural and anthropogenic activities. These activities have created many nutrient pollution sources which affect the survival and sustainability of the Lake Ecosystem. This study was conducted to investigate the transportation of nutrients into the Lake Victoria through the Sondu-Miriu (SM) and the Simiyu-Duma (SD) rivers to represent the changes that have been occurring in many rivers draining the Lake basin. Water samples were collected along the SM and the SD river courses from upstream to the Lake shore. The results showed that the concentration of nitrate ranged between 770 μgL-1 and 970 μgL-1 for SM River and between 400 μgL-1 and 1250 μgL-1 for SD River while for phosphate it ranged from 120 μgL-1 to 270 μgL-1and from 457 μgL-1 to 1175 μgL-1 for SM and SD Rivers, respectively. The estimated nutrient loading through SM were 40ty-1 and 7.9ty-1 while for SD River were 25 ty-1 and 26ty-1 for dissolved inorganic nitrogen and phosphorous, respectively. The spatial variation of the concentrations nitrogen was not significant along the SM while in the SD Rivers the average concentration was lower in downstream than in the middle due to presence of swamp and dam that regulate the flow of water and retain nutrients. The results suggest that the catchment soil and rock are the major sources of the nutrients and their interaction with water dominate the transportation mechanism of the nutrients to the Lake Victoria through the Sondu-Miriu and Simiyu-Duma rivers.