Browsing by Author "Marco, John Andrew Mahugija"

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    Chemo dynamics of pesticides in soil at some hotspots in ten regions and in atmospheric matrices in kibaha Tanzania
    (University of Dar es Salaam, 2011) Marco, John Andrew Mahugija
    This thesis reports on the chemodynamics of pesticides in soil at contaminated sites in ten regions and in atmospheric matrices in Kibaha, Tanzania. Soil samples were extracted using an accelerated solvent extractor with n-hexane:acetone while rainwater samples were extracted by liquid-liquid extraction with dichloromethane. Labelled internal standards were used. Clean-up of extracts of samples was performed by using silica gel and aluminium oxide with 3% water followed by C18 sorbents. Instrumental analysis of extracts was performed by use of a high resolution GC-MS. Very high concentrations of persistent bioaccumulative and toxic organochlorine pesticides and degradation products (e.g. DDT, DDD, DDE, HCHs, endosulfans, dieldrin, aldrin, endrin, hexachlorobenzene, heptachlor and chlordane) have been found in samples from almost all sites and they were widely distributed. The concentrations of the dominant contaminants (e.g. DDT) were up to 560000 mg/kg dw in soil and 3200 μg/l in rainwater samples. The compositions of the contaminants indicated aged compounds in most cases but which have not been significantly degraded in most of the studied areas. The contaminants were evenly distributed among the sampling depths at most sites while there were significant differences in the concentrations of the compounds among the sampling depths in soil at the most contaminated sites. The highest concentrations of the compounds were found at points located within the most affected areas and the concentrations decreased with increase in distance from those points. The concentrations of the compounds in rainwater samples indicated a slight decrease in emissions with time. The findings indicate risk and concern to public health and the environment and thus point out to the urgent need for remedial actions at the most affected areas.
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    Levels of pesticides and metabolites emanating from a point source
    (University of Dar es Salaam, 2004) Marco, John Andrew Mahugija
    This thesis reports on the levels of pesticides and metabolites emanating from a point source, an old storage site at Vikuge Farm in the Coast region Tanzania. 100 pesticides and metabolites were analyzed for in surface water, soil, sediment, and flora samples. Leaves, roots, and stems of eight plant species, were used as passive biomonitors of the spatial distribution of pesticides and metabolites from the point source. GPC cleaned extracts of the samples were analyzed by GC-ECD/NPD. Confirmatory tests were done by GC/MS and LC/MS/MS. The levels of XDDT were up to 1764.4 ng/1 in water, 18274.1 ng/g f.w. in flora samples, 533.9 ng/g d.w. in soil, and 1945.4 ng/g d.w. in sediments. The levels for £HCH were up to 1167.2 ng/1 in water, 73.7 ng/g f.w. in flora samples, 3.9 ng/g d.w. in soil, and 24.6 ng/g d.w. in sediments. The highest levels for other compounds were 29.2 ng/1 for pentachloroanisole in water, 11.1 ng/g f.w. for aldrin, and 7.7 ng/g f.w. for dieldrin in flora samples, 172 ng/1 for atrazine, 18 ng/1 for isoproturon, and 12 ng/1 for diuron in water. Trends similar to previous findings at the point source were observed. There are very strong positive correlations in the concentrations of most of the detected compounds, indicating a common source. The results indicate recent inputs of contaminants from the point source, where degradation is not significant. Mangifera indica (mango) leaves were the best bioindicators of the spatial distribution of pesticide residues, and aerial transport seemed to be the dominant route. Most concentrations of pesticides and metabolites were below the maximum residue limits (MRLs). However, some of the concentrations were higher than the respective MRLs, indicating risk and concern to public health.