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Cycle 6 (2017 Deadline)

Exploring the fate of mercury in artisanal gold mining of the Lake Victoria Gold Field

PI: Clavery Tungaraza,, Sokoine University of Agriculture
U.S. Partner: Mark Cohen, National Oceanic and Atmospheric Administration (NOAA)
Project Dates: December 2017 - November 2020

Project Overview:

This study will investigate quantitative and qualitative mercury availability in the environment surrounding artisanal and small-scale gold mining (ASGM) locations in Tanzania, where mercury contamination is of concern with regard to the health of community members and others who consume food products originating from the area. Although mercury contamination can be lessened by appropriate controls and proper handling methods, such measures are not routinely applied in Tanzania, where mercury has been documented in different environments and studies. Mercury can be transported away from emission sources by riverine systems to large water bodies like Lake Victoria. The resulting fish contamination can be significant, which is a particularly serious issue as fish are the major protein source in the region and the whole country. In Tanzania, very little data is available on levels of methylmercury in biota and sediments and on the contribution that ASGM activities make to these levels. Further, there is little information on the relative importance of riverine and atmospheric processes in transporting mercury from sources to ecosystems.

All these aspects must be taken into accoutn in order to understand the magnitude of mercury impacts on the environment and on human beings. This project will develop data on levels of mercury downwind and downstream from ASGM activities in water, suspended particulate matter, sediments, and fish and improve understanding of spatiotemporal variations of mercury levels. Inclusion of methylmercury in the analysis represents a significant extension of the PI’s earlier work.
Photo courtesy of Dr. Tungaraza

Tanzania is now in the process of ratifying the Minamata Convention, a key goal of which is to raise awareness of health concerns, especially in developing countries, resulting from mercury exposure of vulnerable populations, especially women and children. Mercury emissions from ASGM activities in Tanzania cause food chain contamination that poses direct threats to vulnerable populations under the Convention.

In preparation for ratifying the Minamata Convention, Tanzania needs to establish country-based information on the sources and extent of mercury contamination. The data and analysis generated in this project will help inform policies for protection of water quality and foodstuff safety, as well as provide scientific information to aid the formulation of the legal framework on mercury that will be needed for government regulations.

Summary of Recent Events

In this reporting period, sediments, soil and water samples for total mercury analysis were sampled around and at ASGM sites in central regions; Singida (London, and Sekenke), in the Lake Victoria region; Geita (Nyarugusu, Mgusu and Rwamagasa) and southern highlands; Iringa region (Nyakavalanga, Itengulinyi and Ilhanzutwa) and Mbeya region (Makongolosi and Itumbi) during dry and wet seasons. Depending on the sampling area, soil samples were collected from the surface to 1 metre deep at mining sites. Sediment samples were collected from Mugusu, Nyarugusu and Makongolosi mines where running waters and wetlands are found at the vicinity of the mining sites. Customization of the method for total mercury analyses was done successfully. However, analysis of methyl mercury was not done due to delays of installation of analytical instrument. Methyl mercury analysis and customization of the instrument have been delayed.

Analyses of soil and sediment samples collected during dry and rainy season was completed. Sediments, soil and Water samples from the study were analysed for total mercury (THg) and observed to contain elevated levels of mercury. Again the results have indicated elevated concentrations during the season. The highest recorded concentration in sediment was about 13μg/kg which was recorded in surface sample close to gold processing site. The general trend of mercury concentration in sediments indicated high levels close to mining sites and low levels away from the mining sites. Over 100 analyzed samples the lowest sample concentration was 0.2 μg/kg. Under normal environmental monitoring, this was still higher especially with knowledge that this was sampled about 5 kilometers away from the mining site, downstream.

As part of capacity building one MSc. The student is developing a research proposal on Total mercury quantification in food stuff grown in the mining sites. Earlier plan was to two MSc students. It was difficult getting students studying MSc by coursework and dissertation program at the institution (SUA) with good background in Chemistry therefore, the project had resorted to enrolling students for M.Sc. by research. However, the process was delayed as the University was reviewing all M.Sc by
research curriculum to allow more colleges to enroll students. For the time being the curricular are submitted to Tanzania Commission of Universities (TCU) for quality control, assurance and approval. This caused more delays in enrolling students at SUA. Therefore, the project resorted to enroll students doing M.Sc by coursework and dissertation program with good background in Chemistry from other universities. Two students were earmarked; one from the University of Dar es Salaam and one student from the Nelson Mandela African Institutions of Science and Technology. They are currently developing and aligning their M.Sc. Research proposals to fit into project objectives.

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