Fate of smelter particulates in tropical soils.

Highly polluted topsoil from the vicinity of the Mufulira Cu Smelter (Zambia) and Tsumeb Cu-Pb Smelter (Namibia) were studied to determine the distribution and weathering features of smelter-derived particulates. X-ray diffraction analysis of heavy mineral soil fraction generally detected rock-derived phases (zircons, tourmaline, rutile, residual carbonates) and only rarely metal-bearing phases. However, SEM/EDS identified numerous anthropogenic metal-bearing particles in the most polluted soil layers at both sites. In the Cu-smelting areas, spherical particles mainly composed of covellite (CuS) and chalcocite (Cu2S) were detected, while angular grains of chalcopyrite (CuFeS2) were attributed to mining-derived tailings. Fe-Cu oxide particles were detected along with hydrated Fe-oxides corresponding to secondary weathering products. Laboratory pot experiments were conducted to understand the weathering of smelter dusts in a typical red tropical soil (Oxisol). Dust from the Mufulira Smelter (soluble sulphates) was highly reactive when incubated in soil. The released Cu became bound in the labile soil fraction and was susceptible to vertical migration in the soil profiles, whereas other metal-bearing phases were more resistant to weathering and subsequent release of contaminants.
Highly polluted topsoil from the vicinity of the Mufulira Cu Smelter (Zambia) and Tsumeb Cu-Pb Smelter (Namibia) were studied to determine the distribution and weathering features of smelter-derived particulates. X-ray diffraction analysis of heavy mineral soil fraction generally detected rock-derived phases (zircons, tourmaline, rutile, residual carbonates) and only rarely metal-bearing phases. However, SEM/EDS identified numerous anthropogenic metal-bearing particles in the most polluted soil layers at both sites. In the Cu-smelting areas, spherical particles mainly composed of covellite (CuS) and chalcocite (Cu2S) were detected, while angular grains of chalcopyrite (CuFeS2) were attributed to mining-derived tailings. Fe-Cu oxide particles were detected along with hydrated Fe-oxides corresponding to secondary weathering products. Laboratory pot experiments were conducted to understand the weathering of smelter dusts in a typical red tropical soil (Oxisol). Dust from the Mufulira Smelter (soluble sulphates) was highly reactive when incubated in soil. The released Cu became bound in the labile soil fraction and was susceptible to vertical migration in the soil profiles, whereas other metal-bearing phases were more resistant to weathering and subsequent release of contaminants.