Environmental implications of phytoextraction for mercury and gold : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Earth Science

The overall objective of this study was to investigate how plants could be used to harvest gold (phytomining) and at the same time remove mercury (phytoremediation) from auriferous mercury-contaminated soils. This study was undertaken to find appropriate plants that could be used to harvest gold, residual in mine tailings or in uneconomic low-grade ore, and at the same time remove residual mercury, commonly used to extract the gold in artisanal mining areas. Different procedures involving analytical methodology, leaching of acid mine tailings and the growing of plants in both gold and mercury-bearing substrates were undertaken. The analytical methods involved in the analysis of gold in the laboratory using the modern instruments were Flame Atomic Absorption Spectrometry (FAAS) and Graphite Furnace Atomic Absorption Spectrometry (GFAAS). The determination of mercury involved using Flameless Atomic Absorption Spectrometry. To understand the induced solubility of metals in phytoextraction, Tui mine tailings were leached with several chemicals known to solubilise gold: ammonium thiocyanate, ammonium thiosulphate and urea. The pH of the tailings material was varied through amendment with lime to examine the effect of this geochemical parameter on metal solubility and thus the potential for both plant uptake and leaching. The Tui mine tailings were chosen because of their geochemistry; these are highly weathered sulphide-ore tailings that leach heavy metals into adjacent water systems. The induced-phytoextraction potential of root crops was also examined in this thesis. Five root crops were grown in an artificial substrate consisting of 3.8 mg/kg (ppm) of elemental gold dispersed in sand. The possibility of using these root crops for phytomining was determined by separately adding chelating agents ammonium thiocyanate and ammonium thiosulphate to the substrate. In most cases there was a higher gold concentration in the roots than in the shoots. The highest mean gold concentrations were found in carrot roots and in roots of two radish cultivars. It was concluded that there was some potential for the use of carrot to grow an economic crop of gold from mine tailings. Results obtained from experiments where plants were grown in Tui tailings indicated that both chicory and Brassica juncea could be used for the phytoextraction of gold and mercury in the same crop. Under acidic conditions thiocyanate induced the uptake of gold by Brassica juncea and the uptake of mercury by chicory; and thiosulphate induced the uptake of mercury by chicory, but it did not induce the uptake of gold by the same plant. Under alkaline conditions, treatment with ammonium thiosulphate induced the uptake of gold and mercury by Brassica juncea; and treatment with thiosulphate induced the uptake of mercury by chicory but it did not induce the uptake of gold. It was therefore concluded that, Brassica juncea could be used for phytoextraction of gold and mercury when ammonium thiosulphate is applied to the substrate. Results from the root-crop experiment indicate that, carrots could supersede most of the plants used due to the greater apparent metal-uptake potential. Finally, a model is proposed for field trials to examine the potential of phytoextraction for gold and mercury in Tanzania. The aim of this model is to examine how the positive results obtained from research conducted in the laboratory and greenhouse can be put into practice. The use of similar plants as well as traditional tropical species (e.g. wild cassava - a known accumulator of cyanide) is suggested along with suitable chemical amendments

Determinants of Choice of Institutional Marketing Arrangements by Small Poultry Businesses in Tanzania: Application of Transaction Cost Theory

The transaction cost (TC) theory of the firm provides a conceptual model suitable for investigating the mechanism by which business firms evolve and grow. This paper uses poultry farm businesses (PFBs) in Tanzania as a vehicle of assessing relevance of the theory in explaining factors determining choice of institutional arrangement, for the purpose of identifying policy measures that can influence small business firms to opt for contractual businesses. A cross-sectional survey was conducted in two regions in the country covering 170 respondents. Logistic regression analysis indicate that the choice by business firms to opt for a particular institutional arrangement is determined by all the components of total transaction cost (TTC); as all were statistically significant (P < 0.05). It shows also that search and screening cost has greatest impact on choice of institutional arrangement (Wald = 8.745) followed by enforcement cost (Wald = 4.735) and negotiation cost (Wald = 4.735). It indicates in addition that, probability of PFBs to enter into contractual businesses falls with increase in Transaction Costs (TCs). Linear regression analysis shows, in addition that, search and screening cost has greatest elasticity to TTC (Beta = 0.596), followed by enforcement cost (Beta = 0.43) and negotiation cost (Beta =0.437). A theory based intervention should therefore, mainly be focused on reducing search and screening cost, followed by the other components of TTC.Keywords: Transaction costs, poultry farm businesses, institutional arrangement

Institutional Overlap and Power Relations in Private-Led Regularization Projects in Informal Settlements: The case of Gairo Town, Morogoro

In the early 1990s to date, the private sector has continued to gain momentum in urban planning and service delivery. Among others, the penetration of neo-liberal ideology in policies and legislations empowered the engagement of private sector in urban planning domain. Subsequently many private firms have dominated the process of the preparation of details schemes including regularization of informal settlements in different cities, municipalities and towns in Tanzania. However, the institutional overlap and power relation and approach used by the private sector at the grassroot levels to mobilize resources to meet the cost of regularization of informal settlements are rarely documented and discussed. This paper uses the case of Gairo Town regularization project to illuminate on the existing institutions, actors and power relation in the private-lead regularization projects and approach used to engage the community in financing the preparation of regularization schemes. Through household surveys, official and key informant interviews, observations and mapping, steps followed by the private firms to acquire the projects from the Planning Authority to the community levels were documented and analyzed. The findings show that when there are mutually beneficial interactions among private sector, politicians and grassroots institutions, the community contributes their financial resources to prepare regularization schemes of their settlements. The institutional overlap in terms of multiple allocation of actors in different institutional levels and power relations facilitate the resource mobilization for regularization projects in the informal settlements.

Survey Of Mobile Phone Usage Patterns Among Street Vendors

Abstract: The purpose of this exploratory study i

Productivity premia and firm heterogeneity in Eastern Africa

Productivity development is a key issue for export-driven growth and development. We use East African Community (EAC) firm-level data. Instead of focusing on single EAC partners, using the World Bank Enterprise Surveys, investigate firm-level productivity difference for seven countries that are part of the COMESA-EAC-SADC tripartite free trade area (TFTA). Using export and ownership dimensions, we identify four types of firms: National Domestic, National Exporters, Foreign Domestic and Foreign Exporters. We find a clear export productivity premium for national manufacturing firms and service sectors, but not for foreign owned firms. We also find clear foreign-ownership productivity premium for both domestic and exporting firms in manufacturing sectors but less clear in services sectors. The gap between national export premium and foreign-ownership premium is stronger in manufacturing firms as opposed to service sectors. Moreover, we find clear and strong productivity premia in size, training programmes and level of development in the manufacturing firms. In the services sector, these premia are always smaller and only significant for medium-sized firms. There is no difference in experience premium between sectors in terms of both significance and magnitude of the estimated coefficients

Impact of foot-and-mouth disease on mastitis and culling on a large-scale dairy farm in Kenya

Foot and mouth disease (FMD) is a highly transmissible viral infection of cloven hooved animals associated with severe economic losses when introduced into FMD-free countries. Information on the impact of the disease in FMDV-endemic countries is poorly characterised yet essential for the prioritisation of scarce resources for disease control programmes. A FMD (virus serotype SAT2) outbreak on a large-scale dairy farm in Nakuru County, Kenya provided an opportunity to evaluate the impact of FMD on clinical mastitis and culling rate. A cohort approach followed animals over a 12-month period after the commencement of the outbreak. For culling, all animals were included; for mastitis, those over 18 months of age. FMD was recorded in 400/644 cattle over a 29-day period. During the follow-up period 76 animals were culled or died whilst in the over 18 month old cohort 63 developed clinical mastitis. Hazard ratios (HR) were generated using Cox regression accounting for non-proportional hazards by inclusion of time-varying effects. Univariable analysis showed FMD cases were culled sooner but there was no effect on clinical mastitis. After adjusting for possible confounders and inclusion of time-varying effects there was weak evidence to support an effect of FMD on culling (HR = 1.7, 95% confidence intervals [CI] 0.88-3.1, P = 0.12). For mastitis, there was stronger evidence of an increased rate in the first month after the onset of the outbreak (HR = 2.9, 95%CI 0.97-8.9, P = 0.057)