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Marta Mileusnić, Stanko Ružičić University of Zagreb, Croatia

Trace elements dispersion from a tailings dam and speciation in surroundin g agricultural soils Kombat Mine, Otavi Mountainland, Namibia. Marta Mileusnić, Stanko Ružičić University of Zagreb, Croatia Benjamin Siyowi Mapani, Akalemwa Fred Kamona Isaac Mapaure, Percy Maruwa Chimwamurombe

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Marta Mileusnić, Stanko Ružičić University of Zagreb, Croatia

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  1. Trace elements dispersion from a tailingsdamand speciation in surrounding agricultural soilsKombat Mine, Otavi Mountainland, Namibia Marta Mileusnić, Stanko Ružičić University of Zagreb, Croatia Benjamin Siyowi Mapani, Akalemwa Fred Kamona Isaac Mapaure, Percy Maruwa Chimwamurombe University of Namibia, Namibia

  2. STUDY AREA - Kombat • Grootfontein district • latitude 1943´S • longitude 1743´E • altitude of 1.590 metres • 2 000 inhabitants • Agriculture: • (1) livestock production • (2) maize, potatoes, vegetables • and subtropical fruits

  3. Kombat Cu mine • mining:1962 – 2008 (46 years) • 24,550,280 t of copper ore • tailing dam(about 300 million T) Area: 20 ha • Height: 3-4 m

  4. winter Sub tropical climate Summers -very hot -heavy downpours -northeastery winds Winters (May –June) -mild -dry winters - easterly winds summer

  5. Main agents of material transfer from tailings into surrounding areas WINTER - WIND SUMMER -RAIN WATER (as run-off in episodes of heavy downpours

  6. RESEARCH GOALS (1) to determine lateral distribution and seasonal variability of trace metals, as well as dominant metal binding mechanisms in the agricultural soil (2) to identify dominant type of metal dispersion from the tailings impoundment (mechanical or chemical) (3) to carry out preliminary assessment of environmental risk associated with tailings dam

  7. 1) tailings SAMPLING - after results of Kribek et al. (2006) 2) polluted soil 3) control soil • 2 sampling campaigns: • Wet season – march • Dry season – august

  8. Analytical work (1) bulk mineralogy of soils and tailings (XRD) (2) Pseudototal metal content of soils and tailings (aqua regia digestion, AAS) (3) Binding sites of metals (sequential leaching, AAS)

  9. Modified after: TESSIER et al. (1979) and SULKOWSKI et al. (2006)

  10. RESULTS Mineral content tailings: calcite and dolomite, quartz, micaceous material, +/-gypsum soil: quartz, calcite, dolomite, K-feldspar, plagioclase, clay minerals. pH tailings: circum-neutral (7.0-7.7) soil: alkaline (8.1-8.6)

  11. Pseudototal metal concentrations(median values in mg/kg) - no seasonal variation in concentrations Canadian soil quality guidelines (CECME, 1999) for agricultural soils

  12. Cu Pb Metals binding forms in polluted soils

  13. CONCLUSIONS (1) Cu and Pb showed significantly high concentration in tailings. (2) Cu and Pb in all analysed samples of farmland soils west of the tailings dam exceed maximal allowed values for agricultural soils. (3) Seasonal variations - not observed. (4) The main binding site for Cu and Pb is oxide fraction

  14. (5) mechanical dispersion of elements from tailings dam prevails (6) carbonate minerals dominate in tailings - drainage is neutralized -lead and copper immobile (7) Pb and Curelatively strongly bound to the soils + high pH of soil- small risk for their release in soil water and to groundwater (8) study by Casteel et al. (2006) - lead associated with iron oxide shows intermediate bioaccesibility while ingested (9) Rehabilitation of tailings dam necessary

  15. THANK YOU FOR YOUR ATTENTION

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