No description available.

No description available.

The current urban infrastructure and demographic development of Uganda and in particular of Kampala city is rapid and does not correspond to the planned socio-economic and industrial infrastructure. This project was justified by the existence of numerous peri-urban areas with unplanned and no monitored san-itary as well as water supply systems. The unsanitary handling and disposal, of domestic and industrial solid waste, sewerage and small car related industries pose a serious threat to the quality of the groundwater resources. Field studies were conducted at different occasions between February and March 2012. These included soil and water sampling in and around five protected springs for analysis of the concentrations of four trace metals: Cu, Pb, Cd and Zn. The method used for leaching tests of the soil samples was the European Standard ISO/TS21268-1, and the samples produced were analyzed in a ICP-MS. Addi-tionally, metal concentrations and dissolved organic content of water samples were analyzed. The ICP-MS results showed that the concentration of the trace metals in the waters were below guideline values stated by the WHO, which implies that the residents are not exposed to notable trace metal contamination in the drinking water. As the total metal content in the soils were below the Swedish Environmental Protection Agency (Swedish EPA) guidelines, it was assumed that trace metal contamination was not of significance under the pre-vailing circumstances. However, the leachable metal contents in a number of the soils were high, which may pose a future risk to groundwaters.

Relationships between trace metals and nanoparticles were investigated using analytical transmission electron microscopy (aTEM) and asymmetric flow field flow fractionation (aFlFFF) coupled to both multi-angle laser light scattering (MALLS) and high resolution-inductively coupled plasma mass spectroscopy (HR-ICPMS). Riverbed sediment samples were taken from the Clark Fork River in Montana, USA where a large-scale dam removal project has released reservoir sediment contaminated with toxic trace metals (namely Pb, Zn, Cu and As) which accumulated from one and a half centuries of mining activities upstream. An aqueous extraction method was used to attempt to separate the nanoparticles from the bulk sediment. After analysis of initial results, it was found that low density clays were being selected for in this process and made up a major portion of the particles within the extracts. However, it was also realized that the metals of interest were associated almost exclusively with nano-sized Fe and Ti oxides. In order to more fully examine these relationships, a density separation method, using sodium polytungstate (2.8g/cm3), was developed to separate these higher density oxides from the lower density clays. The heavy fraction was then subjected to an aqueous extraction routine to extract the nanoparticulate fraction. FFF results indicated a smaller size distribution and more ideal fractionation with this method. The aFlFFF-HR-ICPMS profiles for Fe and Ti also matched strongly with the data for the trace metals. The majority of particles analyzed with the TEM were nano-sized Fe and Ti oxides (most commonly goethite, ferrihydrite and brookite), which typically had trace metals associated with them. In many cases, it was aggregates of these nano oxides that were found hosting trace metals. Nanoparticles and aggregates are known to behave differently than their bulk mineral phases or constituent particles, respectively. Nanoparticles are also capable of extended transport in the environment. For these reasons, it is important that their associations with toxic trace metals be extensively evaluated, as they will affect the bioavailability and toxicity of these metals with implications for any type of contaminant sediment relocation, dam removal or metal contaminated site. / Ph. D.

No description available.