Institute of Development Studies

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Start date: 2007End date: 2009

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    Use of chicken manure extract for biostimulation and enhancement of perchlorate rhizodegradation in soil and water media
    (Taylor & Francis Online, 2007) Mwegoha, William J. S.; Mbuya, Odemari S.; Jai, Amita; Ugochukwu, Ngozi H.; Abazinge, Michael D.
    The influence of biostimulation using dissolved organic carbon (DOC) on rhizodegradation of perchlorate and plant uptake was studied under greenhouse conditions using soil and hydroponic bioreactors. One set of bioreactors planted with willow (Salix babylonica) plants was spiked with 300 mg L−1 DOC in the form of chicken manure extract, whereas a second set was not treated with DOC. A similar experiment without willow plants was run in parallel to the planted bioreactors. The planted soil bioreactors amended with DOC reduced perchlorate from 65.85 to 2.67 mg L−1 in 21 days for humic soil (95.95% removal) and from 68.99 to 0.06 mg L− 1 for sandy loam (99.91% removal) in 11 days. Nonplanted DOC treated soil bioreactors achieved complete perchlorate removal in 6 and 8 days for humic and sandy loam, respectively. Both planted and nonplanted soil bioreactors without DOC removed > 95% perchlorate within 8 days. Planted soil bioreactors respiked with perchlorate reduced perchlorate to nondetectable levels in 6 days. Hydroponics experiment amended with DOC reduced perchlorate from approximately 100 mg L− 1 to nondetectable levels within 7 to 9 days. Hydroponic bioreactors without DOC had low perchlorate removal rates, achieving 30% removal in 42 days. Leaf samples from sandy loam soil bioreactors without DOC had four times perchlorate phytoaccumulation than the DOC-treated plants. Similar results were obtained with the nonplanted bioreactors. Persistence of perchlorate in solution of planted hydroponic bioreactors without DOC amendment suggested that natural DOC from the plant exudates was not enough to biostimulate perchlorate reducing microbes. The hydroponic bioreactor study provided evidence that DOC is a limiting factor in the rhizodegradation of perchlorate.
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    The use of phytoremediation technology for abatement soil and groundwater pollution in Tanzania: opportunities and challenges
    (Journal of Sustainable Development in Africa, 2008) Mwegoha, William J. S.
    Contamination of soil and groundwater from anthropogenic sources is a major concern in many developing countries including Tanzania. Improper handling of Municipal Solid Wastes (MSW) in many urban centers in Tanzania has often resulted into gas emissions and generation of leachate, which pose threat to the environment. Additionally, the use of pesticides for agricultural purposes is on the increase because of the need to improve crop production and control of pests, weed infestation and insect outbreaks. As a consequence, pesticide use has caused adverse contamination in soils and waters. The potentially negative impacts of these pesticide stocks on humans and the environment are of major concern. To make the situation more challenging, the country has experienced a substantially fast growth of the mining sector in many parts of the country over the past ten years, which has resulted in reported soil and water pollution from acid mine drainage with elevated concentrations of heavy metals. It is estimated that more than 30% of the Tanzanians depend on groundwater as their source of water. Most of the conventional methods for environmental remediation of these sites are expensive and often poorly implemented or not implemented at all. Thus, there is a clear need to develop new cost effective and environmentally friendly clean-up methods to remediate the contaminated areas in Tanzania. Phytoremediation is a relatively new and promising technology that uses plants to degrade, stabilize, metabolize or sequester potentially toxic compounds from the environment. This paper is aimed at assessing the potential of phytoremediation as a low-cost alternative, but which has yet to be studied and used in Tanzania.