elements dispersion from a tailings dam and speciation in 微量元素扩散的尾矿坝和形态ppt课件.ppt

Trace elements dispersion from a tailings dam and speciation in surrounding agricultural soilsKombat Mine, Otavi Mountainland, Namibia; 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 ; Kombat Cu mine ;winter; Main agents of material transfer from tailings into surrounding areas WINTER - WIND SUMMER - RAIN WATER (as run-off in episodes of heavy downpours; 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 ; SAMPLING - after results of Kribek et al. (2006) ; 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) ;Fraction; 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) ;Pseudototal metal concentrations (median values in mg/kg) - no seasonal variation in concentrations Canadian soil quality guidelines (CECME, 1999) for agricultural soils;Metals binding forms in polluted soils; 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 ;(5) mechanical dispersion of elements from tailings dam prevails (6) carbona