Search

Carbonate breccias dissociated from their platform top counterparts are little studied despite their potential to reveal the nature of past shallow-water carbonate systems and the sequential alteration of such systems. A petrographic and stable isotopic study allowed evaluation of the sedimentological and diagenetic variability of the Cenozoic Batu Gading Limestone breccia of Borneo. Sixteen lithofacies representing six facies groups have been identified mainly from the breccia clasts on the basis of shared textural and compositional features. Clasts of the breccia are representative of shallow carbonate platform top and associated flank to basinal deposits. Dominant inputs are from rocky (karstic) shorelines or localised seagrass environments, coral patch reef and larger foraminiferal-rich deposits. Early, pre-brecciation alteration (including micritisation, rare dissolution of bioclasts, minor syntaxial overgrowth cementation, pervasive neomorphism and calcitisation of bioclasts and matrix) was mainly associated with marine fluids in a near surface to shallow burial environment. The final stages of pre-brecciation diagenesis include mechanical compaction and cementation of open porosity in a shallow to moderate depth burial environment. Post-brecciation diagenesis took place at increasingly moderate to deep burial depths under the influence of dominantly marine burial fluids. Extensive compaction, circum-clast dissolution seams and stylolites have resulted in a tightly fitted breccia fabric, with some development of fractures and calcite cements. A degree of facies-specific controls are evident for the pre-brecciation diagenesis. Pervasive mineralogical stabilisation and cementation have, however, led to a broad similarity of diagenetic features in the breccia clasts thereby effectively preserving depositional features of near-original platform top and margin environments. There is little intra-clast alteration overprint associated with subsequent clast r

Bag house dust and four different slags (converter, reverb, ausmelt slags and slag dust) from the Tsumeb Copper Smelter (Namibia) were studied. The pH-static leaching tests (pH range 3-12) were used and contaminant leachabilities at natural pH were compared with EU criteria for non-hazardous and hazardous wastes. Bag house dust exhibited high leaching of As (up to 314 g/kg) and exceeded the limit value for hazardous waste by more than 2 000 times. The leaching of contaminants from slags was more pH-dependent, with highest Cu and Pb release under acidic conditions (up to 1 780 and 752 mg/kg, respectively). Metal leaching at natural pH was very low, far below the limits for non-hazardous wastes. Arsenic exhibited V-shaped leaching patterns with minimum at pH 6 for all the slag samples. Extremely high levels of As were found to be leaching from the bag house dust whereas they only exceeded the limit for hazardous waste from ausmelt slags. Safety measures are currently adopted in the smelter to protect the workers from bag house dusts. The risk of contaminant leaching from slag particles wind-deposited in soils seems to be limited., Bag house dust and four different slags (converter, reverb, ausmelt slags and slag dust) from the Tsumeb Copper Smelter (Namibia) were studied. The pH-static leaching tests (pH range 3-12) were used and contaminant leachabilities at natural pH were compared with EU criteria for non-hazardous and hazardous wastes. Bag house dust exhibited high leaching of As (up to 314 g/kg) and exceeded the limit value for hazardous waste by more than 2 000 times. The leaching of contaminants from slags was more pH-dependent, with highest Cu and Pb release under acidic conditions (up to 1 780 and 752 mg/kg, respectively). Metal leaching at natural pH was very low, far below the limits for non-hazardous wastes. Arsenic exhibited V-shaped leaching patterns with minimum at pH 6 for all the slag samples. Extremely high levels of As were found to be leaching from the bag house dust whereas they only exceeded the limit for hazardous waste from ausmelt slags. Safety measures are currently adopted in the smelter to protect the workers from bag house dusts. The risk of contaminant leaching from slag particles wind-deposited in soils seems to be limited.

Two sites in the semi-arid Otavi Mountain Land in NE Namibia have been investigated. At Berg Aukas, V rich mine tailings are over 30 years old, but most V remains in primary descloizite embedded in carbonate matrix. Released V was incorporated into ferric hydroxides later transformed to haematite. In contrast, released Zn and Pb were incorporated into smithsonite and cerussite, which are less stable from environmental viewpoint. At Kombat mine tailings, As released from pyrite was also incorporated into haematite, but Cu from dissolution of chalcopyrite and bornite precipitated as malachite and cerussite, which are also much less stable than haematite. It seems that formation of haematite, which is relatively fast in tropical climate conditions, is favourable for attenuation of contaminants released into pore water. (Authors.), Two sites in the semi-arid Otavi Mountain Land in NE Namibia have been investigated. At Berg Aukas, V rich mine tailings are over 30 years old, but most V remains in primary descloizite embedded in carbonate matrix. Released V was incorporated into ferric hydroxides later transformed to haematite. In contrast, released Zn and Pb were incorporated into smithsonite and cerussite, which are less stable from environmental viewpoint. At Kombat mine tailings, As released from pyrite was also incorporated into haematite, but Cu from dissolution of chalcopyrite and bornite precipitated as malachite and cerussite, which are also much less stable than haematite. It seems that formation of haematite, which is relatively fast in tropical climate conditions, is favourable for attenuation of contaminants released into pore water. (Authors.)

Dusts from metal smelters in the Zambian Copperbelt and northern Namibia were investigated using a combination of mineralogical techniques (XRD, SEM/EDS, TEM/EDS) in order to understand the solid speciation of the contaminants, as well as their bioaccessibility using in vitro tests in simulated gastric and lung fluids to assess the exposure risk for humans. The leaching of metals was mainly dependent on the contaminant mineralogy. A potential risk can be recognised, particularly from ingestion of the dust, with bioaccessible fractions ranging from 5 to 89% of the total contaminant concentrations. Relatively low bioaccessible fractions were observed for simulated lung fluid extracts (carried out only on Zambian dusts), with values ranging from 0.01% (Pb) up to 16.5% (Co) of total contaminant concentrations. Daily intakes calculated for adult oral exposure slightly exceeded the tolerable daily intake limits for Co, Pb, and As., Dusts from metal smelters in the Zambian Copperbelt and northern Namibia were investigated using a combination of mineralogical techniques (XRD, SEM/EDS, TEM/EDS) in order to understand the solid speciation of the contaminants, as well as their bioaccessibility using in vitro tests in simulated gastric and lung fluids to assess the exposure risk for humans. The leaching of metals was mainly dependent on the contaminant mineralogy. A potential risk can be recognised, particularly from ingestion of the dust, with bioaccessible fractions ranging from 5 to 89% of the total contaminant concentrations. Relatively low bioaccessible fractions were observed for simulated lung fluid extracts (carried out only on Zambian dusts), with values ranging from 0.01% (Pb) up to 16.5% (Co) of total contaminant concentrations. Daily intakes calculated for adult oral exposure slightly exceeded the tolerable daily intake limits for Co, Pb, and As.

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.

The cobalt, copper, manganese and lead contents and the 206Pb/207Pb isotope ratios in pine tree rings and soils at sites close to the Nkana smelter and a roadway in the vicinity of Kitwe and at sites in a remote area were determined using inductively coupled plasma-mass spectroscopy. The copper content of the tree rings was in the range 2-40 mg/kg and was higher in the vicinity of the smelter, increasing after 1975; the cobalt content of the tree rings was in the range 0.05-0.07 mg/kg with the highest cobalt contents corresponding to maximum ore production in the mid-1970s; the manganese content of the tree rings was in the range 5-125 mg/kg with acidification through sulphur dioxide emissions indicative of increased manganese contents from the mid-1980s; and the lead content of the tree rings was 0.02-0.7 mg/kg. The isotopic composition of the tree rings and the soil (206Pb/207Pb) was in the ranges 1.16-1.34 and 1.18-1.35, respectively, and was formed by a combination of lithogenic lead, combustion of leaded petroleum, and lead in processed ores., The cobalt, copper, manganese and lead contents and the 206Pb/207Pb isotope ratios in pine tree rings and soils at sites close to the Nkana smelter and a roadway in the vicinity of Kitwe and at sites in a remote area were determined using inductively coupled plasma-mass spectroscopy. The copper content of the tree rings was in the range 2-40 mg/kg and was higher in the vicinity of the smelter, increasing after 1975; the cobalt content of the tree rings was in the range 0.05-0.07 mg/kg with the highest cobalt contents corresponding to maximum ore production in the mid-1970s; the manganese content of the tree rings was in the range 5-125 mg/kg with acidification through sulphur dioxide emissions indicative of increased manganese contents from the mid-1980s; and the lead content of the tree rings was 0.02-0.7 mg/kg. The isotopic composition of the tree rings and the soil (206Pb/207Pb) was in the ranges 1.16-1.34 and 1.18-1.35, respectively, and was formed by a combination of lithogenic lead, combustion of leaded petroleum, and lead in processed ores.

Samples of cassava leaves, cassava tubers and soil were collected from contaminated and uncontaminated areas of the Zambian Copperbelt mining district and the metals (copper, cobalt, zinc, lead and iron) and arsenic contents were analysed by flame or hydride-generation atomic absorption spectroscopy. The contents of copper in leaves of cassava growing on contaminated soils were up to 612 mg/kg Cu total dry weight, compared to up to 252 mg/kg Cu in cassava leaves growing on uncontaminated soils. The contents of cobalt, arsenic and zinc in leaves of cassava growing on contaminated soils were found to be higher than those from uncontaminated areas, while the contents of lead in the leaves of plants from both areas were low and did not differ significantly. The metals contents in the tubers of plants from both areas were markedly lower than those in the leaves. A dietary risk assessment of copper, lead and arsenic indicated no excessive intake of copper, but an occasional excessive intake of lead and arsenic in both contaminated and uncontaminated areas. The surfaces of leaves of cassava growing near the smelters were strongly contaminated by metalliferous dust and were considered to pose a health risk if the cassava were poorly washed., Samples of cassava leaves, cassava tubers and soil were collected from contaminated and uncontaminated areas of the Zambian Copperbelt mining district and the metals (copper, cobalt, zinc, lead and iron) and arsenic contents were analysed by flame or hydride-generation atomic absorption spectroscopy. The contents of copper in leaves of cassava growing on contaminated soils were up to 612 mg/kg Cu total dry weight, compared to up to 252 mg/kg Cu in cassava leaves growing on uncontaminated soils. The contents of cobalt, arsenic and zinc in leaves of cassava growing on contaminated soils were found to be higher than those from uncontaminated areas, while the contents of lead in the leaves of plants from both areas were low and did not differ significantly. The metals contents in the tubers of plants from both areas were markedly lower than those in the leaves. A dietary risk assessment of copper, lead and arsenic indicated no excessive intake of copper, but an occasional excessive intake of lead and arsenic in both contaminated and uncontaminated areas. The surfaces of leaves of cassava growing near the smelters were strongly contaminated by metalliferous dust and were considered to pose a health risk if the cassava were poorly washed.

Samples of topsoil were collected from a large zone in the vicinity of the Nkana copper smelter, from the Chingola mining area and from the Nkana-Kitwe smelting area, and a soil profile (Oxisol) 100 cm in depth was sampled close to the smelter stack. The spatial distribution of arsenic, cobalt, copper, lead and zinc indicated that the highest concentrations were downwind, i.e. northwest, of the smelter. The highest concentrations (mg/kg) in the topsoils were arsenic (255), cobalt (606), copper (27 410), lead (480) and zinc (450). Investigation of the soil profile using lead isotopic tracing and sequential extraction procedures showed that lead exhibited a downward migration with an estimated penetration rate of 1.36 cm/y and that copper also had a significant mobility. Bioaccessibility, determined using simulated gastric conditions, in the smelting area was up to 100% of total lead and arsenic, compared to 81 and 84%, respectively, in the mining area, with the bioaccessibilities of cobalt, copper and zinc being similar for the two areas. The calculated amounts of ingested materials exceeding tolerable daily intake values suggested that the ecotoxicological risks related to soil ingestion were significant for copper and cobalt., Samples of topsoil were collected from a large zone in the vicinity of the Nkana copper smelter, from the Chingola mining area and from the Nkana-Kitwe smelting area, and a soil profile (Oxisol) 100 cm in depth was sampled close to the smelter stack. The spatial distribution of arsenic, cobalt, copper, lead and zinc indicated that the highest concentrations were downwind, i.e. northwest, of the smelter. The highest concentrations (mg/kg) in the topsoils were arsenic (255), cobalt (606), copper (27 410), lead (480) and zinc (450). Investigation of the soil profile using lead isotopic tracing and sequential extraction procedures showed that lead exhibited a downward migration with an estimated penetration rate of 1.36 cm/y and that copper also had a significant mobility. Bioaccessibility, determined using simulated gastric conditions, in the smelting area was up to 100% of total lead and arsenic, compared to 81 and 84%, respectively, in the mining area, with the bioaccessibilities of cobalt, copper and zinc being similar for the two areas. The calculated amounts of ingested materials exceeding tolerable daily intake values suggested that the ecotoxicological risks related to soil ingestion were significant for copper and cobalt.