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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.

The bioaccessibility of metals and arsenic in topsoils around the Rosh Pinah Pb-Zn mine was tested with an in vitro method using a simulated gastric fluid. Gastric accessible contents of chemical elements in topsoil were found to increase in the ascending sequence: Fe (6.2%):As (8.6%):Cu (23.6%):Zn (39.3%):Mn (66.7%):Pb (85.9%). The evaluation of obtained data on gastric bioaccessibility indicates that a health risk related to soil or dust ingestion should be taken into account only in the case of lead. The areal extend to the area contaminated by dust fallout was verified by studying the distribution of metals in the subaerial parts of grass pasture. Dispersion modelling of suspended dust particles (TSP) in the air revealed that while the whole surface of the tailings dam was dry in the past due to infiltration and evaporation of water, the average yearly concentrations of TPS in the Rosh Pinah town amounted to 100-300 microgram/m3, but when two thirds of tailings dam surface has been covered with water, the concentrations of TPS markedly decreased to 30-100 microgram/m3. The results of dispersion modelling fit well with the results of ground geochemical surveys., The bioaccessibility of metals and arsenic in topsoils around the Rosh Pinah Pb-Zn mine was tested with an in vitro method using a simulated gastric fluid. Gastric accessible contents of chemical elements in topsoil were found to increase in the ascending sequence: Fe (6.2%):As (8.6%):Cu (23.6%):Zn (39.3%):Mn (66.7%):Pb (85.9%). The evaluation of obtained data on gastric bioaccessibility indicates that a health risk related to soil or dust ingestion should be taken into account only in the case of lead. The areal extend to the area contaminated by dust fallout was verified by studying the distribution of metals in the subaerial parts of grass pasture. Dispersion modelling of suspended dust particles (TSP) in the air revealed that while the whole surface of the tailings dam was dry in the past due to infiltration and evaporation of water, the average yearly concentrations of TPS in the Rosh Pinah town amounted to 100-300 microgram/m3, but when two thirds of tailings dam surface has been covered with water, the concentrations of TPS markedly decreased to 30-100 microgram/m3. The results of dispersion modelling fit well with the results of ground geochemical surveys.

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.

A study is presented of the stability of nonferrous metal smelting wastes in Europe and Africa and their effects on the adjacent soil environment. Slag, fly-ash and soil samples from smelting sites at Pribram, Czech Republic (primary and secondary lead), Tsumeb, Namibia (copper-lead-arsenic) and Kitwe-Nkana, Mufulira and Chambishi, Zambian Copperbelt (copper-cobalt) were studied using a range of analytical techniques as well as long-term and pH-static laboratory leaching experiments and soil mobility/bioavailability tests. For the Pribram site, the data from leaching experiments showed that higher amounts of lead are released from the primary than from the secondary lead slag and the latter material (slag from car-battery processing) is relatively stable, the released amounts of lead being low, even after long-term (12 y) interaction with water. For zinc, the concentrations released from primary lead slag were found to exceed the European Union regulatory limit for hazardous waste by about ten-fold and by more than 40-fold after 1 and 12 y of leaching, respectively. Leaching experiments carried out on slags from the Tsumeb site showed a high risk of arsenic and antimony release, with arsenates having a tendency to form efflorescence secondary minerals on the slag surfaces., A study is presented of the stability of nonferrous metal smelting wastes in Europe and Africa and their effects on the adjacent soil environment. Slag, fly-ash and soil samples from smelting sites at Pribram, Czech Republic (primary and secondary lead), Tsumeb, Namibia (copper-lead-arsenic) and Kitwe-Nkana, Mufulira and Chambishi, Zambian Copperbelt (copper-cobalt) were studied using a range of analytical techniques as well as long-term and pH-static laboratory leaching experiments and soil mobility/bioavailability tests. For the Pribram site, the data from leaching experiments showed that higher amounts of lead are released from the primary than from the secondary lead slag and the latter material (slag from car-battery processing) is relatively stable, the released amounts of lead being low, even after long-term (12 y) interaction with water. For zinc, the concentrations released from primary lead slag were found to exceed the European Union regulatory limit for hazardous waste by about ten-fold and by more than 40-fold after 1 and 12 y of leaching, respectively. Leaching experiments carried out on slags from the Tsumeb site showed a high risk of arsenic and antimony release, with arsenates having a tendency to form efflorescence secondary minerals on the slag surfaces.

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.

The experimental determination of the rate of weathering and arsenic release from gold-bearing sulphide oresduring mining of the Mokrsko-West deposit, Czech Republic, were studied; it is particularly relevant because of the close proximity of the deposit to the Vltava River, a source of Prague's drinking water. Batch and column leaching experiments were carried out on crushed and homogenised ore material; the most important reactions controlling metal leaching included oxidation of sulphides, carbonate equilibrium, and precipitation of hydrated ferric oxides. The latter were important sorbents of mobilised arsenic. The highest concentration of As in the leachates was from the 64-1 000 micrometre fraction; the oxidation rate was an order of magnitude higher in the agitated batch than in the static column experiment., The experimental determination of the rate of weathering and arsenic release from gold-bearing sulphide oresduring mining of the Mokrsko-West deposit, Czech Republic, were studied; it is particularly relevant because of the close proximity of the deposit to the Vltava River, a source of Prague's drinking water. Batch and column leaching experiments were carried out on crushed and homogenised ore material; the most important reactions controlling metal leaching included oxidation of sulphides, carbonate equilibrium, and precipitation of hydrated ferric oxides. The latter were important sorbents of mobilised arsenic. The highest concentration of As in the leachates was from the 64-1 000 micrometre fraction; the oxidation rate was an order of magnitude higher in the agitated batch than in the static column experiment.

Three types of smelting slags were studied from historically different smelting technologies, the processing of carbonate/oxide ore in a Cu-Pb smelter (1907-1948), Cu and Pb smelting of sulphide ores (1963-1970) and granulated Cu smelting slags (1980-2000). The slags are significantly enriched in metals and metalloids. Slags from the oldest technology are composed of primary Ca- and Pb-bearing feldspars, spinels, complex Cu-Fe and Cu-Cr oxides, delafossite-mcconnellite phases and Ca-Pb arsenates. The presence of arsenates indicates that the slags underwent long-term alteration. More recent slags are composed of high-temperature phases including Ca-Fe aluminosilicates, Pb- and Zn-rich glass, spinel oxides and small sulphide/metallic inclusions embedded in glass. Secondary alteration products that developed on the surface of slags exposed to weathering included highly soluble complex Cu-Pb-(Ca) arsenates associated with litharge and hydrocerussite. Short-term batch leaching tests and speciation solubility modelling showed that As in the leachate exceeded the EU regulatory limit for hazardous waste materials and the toxicity limits defined by USEPA were exceeded for Cd, Pb and As. Complex arsenates are the most important solubility controls for metals and metalloids and these phases can readily dissolve during the rainy season and flush significant amounts of As, Pb and Cu into the environment in the vicinity of the slag dumps., Three types of smelting slags were studied from historically different smelting technologies, the processing of carbonate/oxide ore in a Cu-Pb smelter (1907-1948), Cu and Pb smelting of sulphide ores (1963-1970) and granulated Cu smelting slags (1980-2000). The slags are significantly enriched in metals and metalloids. Slags from the oldest technology are composed of primary Ca- and Pb-bearing feldspars, spinels, complex Cu-Fe and Cu-Cr oxides, delafossite-mcconnellite phases and Ca-Pb arsenates. The presence of arsenates indicates that the slags underwent long-term alteration. More recent slags are composed of high-temperature phases including Ca-Fe aluminosilicates, Pb- and Zn-rich glass, spinel oxides and small sulphide/metallic inclusions embedded in glass. Secondary alteration products that developed on the surface of slags exposed to weathering included highly soluble complex Cu-Pb-(Ca) arsenates associated with litharge and hydrocerussite. Short-term batch leaching tests and speciation solubility modelling showed that As in the leachate exceeded the EU regulatory limit for hazardous waste materials and the toxicity limits defined by USEPA were exceeded for Cd, Pb and As. Complex arsenates are the most important solubility controls for metals and metalloids and these phases can readily dissolve during the rainy season and flush significant amounts of As, Pb and Cu into the environment in the vicinity of the slag dumps.

Chemical and mineralogical analysis of slags, slag-contaminated and slag-free soils and stream sediments with leaching experiments and speciation modelling determine the environmental impact over 10 km2 of smelting activities from the 14th to the 16th century. Three subtypes of pyrometallurgical slags occur: porous slag, equilibrated massive and undercooled massive slag, each having different phase compositions. All slags still contain up to 1.4 wt% Cu, 1 wt% Zn, 750 ppm Pb and 300 ppm As. Leachates from a stream-water solution and distilled water contain lower concentrations of metal(loid)s than leachates from a citric solution, as shown in simple 24 h laboratory experiments. Release of metal(loid)s is higher for porous than for massive slags. Chemical analysis of soils, stream sediments and surface water indicate that some elements reach concentrations exceeding environmentally permissible standards, especially in soils. Pb isotopes were used to trace the impact of various sources of pollution, including modern airborne contamination not related to slag disposal. Slag texture and porosity, phase composition derived from the cooling rates of the slag melt, and environmental conditions are the most important factors controlling slag weathering and metal(loid) release., Chemical and mineralogical analysis of slags, slag-contaminated and slag-free soils and stream sediments with leaching experiments and speciation modelling determine the environmental impact over 10 km2 of smelting activities from the 14th to the 16th century. Three subtypes of pyrometallurgical slags occur: porous slag, equilibrated massive and undercooled massive slag, each having different phase compositions. All slags still contain up to 1.4 wt% Cu, 1 wt% Zn, 750 ppm Pb and 300 ppm As. Leachates from a stream-water solution and distilled water contain lower concentrations of metal(loid)s than leachates from a citric solution, as shown in simple 24 h laboratory experiments. Release of metal(loid)s is higher for porous than for massive slags. Chemical analysis of soils, stream sediments and surface water indicate that some elements reach concentrations exceeding environmentally permissible standards, especially in soils. Pb isotopes were used to trace the impact of various sources of pollution, including modern airborne contamination not related to slag disposal. Slag texture and porosity, phase composition derived from the cooling rates of the slag melt, and environmental conditions are the most important factors controlling slag weathering and metal(loid) release.

To discriminate possible anthropogenic and lithogenic sources of Pb in Lower Silesia, the Pb isotope composition was investigated in rocks, anthropogenic materials and within 10 soil profiles. Silicate rocks have 206-Pb/207-Pb ratios that vary from 1.17 for serpentinites to 1.38 for gneisses and this variability is reflected in the isotope composition of mineral soil horizons. The 206-Pb/207-Pb ratios for coal, ores and anthropogenic slags and fly ashes range from 1.17 to 1.18. Similar ratios were observed in ore and coal samples from Upper Silesia and in the organic-rich O soil horizons, in which their heterogeneity increases with depth in soil profiles. Five soils with varying Pb concentrations, far from contamination centres, show consistent, approximately two-fold enrichment in Pb concentration from the C to the A horizons, consistent with natural re-distribution of Pb within the profiles. The increase in Pb concentration is accompanied by a decrease in Pb isotope ratios, also attributed to natural isotope fractionation. Four soil profiles from industrial areas show variable enrichments in Pb concentrations attributed to anthropogenic input from airborne pollutants or slag particles at smelting sites. The implication is that a lithogenic Pb source can deviate from the basement rock composition, so detailed isotope characteristics of geological background and natural enrichments in soils are often needed to determine lithogenic/anthropogenic proportions of Pb in soils., To discriminate possible anthropogenic and lithogenic sources of Pb in Lower Silesia, the Pb isotope composition was investigated in rocks, anthropogenic materials and within 10 soil profiles. Silicate rocks have 206-Pb/207-Pb ratios that vary from 1.17 for serpentinites to 1.38 for gneisses and this variability is reflected in the isotope composition of mineral soil horizons. The 206-Pb/207-Pb ratios for coal, ores and anthropogenic slags and fly ashes range from 1.17 to 1.18. Similar ratios were observed in ore and coal samples from Upper Silesia and in the organic-rich O soil horizons, in which their heterogeneity increases with depth in soil profiles. Five soils with varying Pb concentrations, far from contamination centres, show consistent, approximately two-fold enrichment in Pb concentration from the C to the A horizons, consistent with natural re-distribution of Pb within the profiles. The increase in Pb concentration is accompanied by a decrease in Pb isotope ratios, also attributed to natural isotope fractionation. Four soil profiles from industrial areas show variable enrichments in Pb concentrations attributed to anthropogenic input from airborne pollutants or slag particles at smelting sites. The implication is that a lithogenic Pb source can deviate from the basement rock composition, so detailed isotope characteristics of geological background and natural enrichments in soils are often needed to determine lithogenic/anthropogenic proportions of Pb in soils.

The leaching behaviour of fly ash from a Co smelter in the Zambian Copperbelt was studied as a function of pH using the pH-static leaching test CEN/TS 14 997. The results were combined with the Orchestra modelling framework and a detailed mineralogical investigation was performed on the original ash and leached solid residues. The largest amounts of Co, Cu, Pb, and Zn were leached at pH 5, generally with the lowest concentrations between pH 9 and 11 and slightly increased concentrations at pH 12. For most elements, the released concentrations were very similar after 48 h and 168 h, indicating near-equilibrium conditions in the system. Calcite, clinopyroxenes, quartz and amorphous phases predominated in the fly ash. Various metal sulphides, alloys and the presence of Cu, Co and Zn in silicates and glass were detected using SEM/EDS and/or TEM/EDS. The leaching of metals was mainly due to dissolution of metallic particles. Partial dissolution of silicate and glass fractions was assumed to significantly influence the release of Ca, Mg, Fe, K, Al, and Si as well as Cu, Co and Zn. Illite was suggested by Orchestra to control the leaching of major elements, whereas Co and Zn were controlled by CoO and zincite respectively. Sorption of metals on hydrous ferric oxides was assumed to be important, especially for the release of Pb and Cu. There is a high risk of Co, Cu, Pb, and Zn mobility in acidic soils around the smelter, therefore potential local options for stabilisation of fly ash were evaluated using the PHREEQC code., The leaching behaviour of fly ash from a Co smelter in the Zambian Copperbelt was studied as a function of pH using the pH-static leaching test CEN/TS 14 997. The results were combined with the Orchestra modelling framework and a detailed mineralogical investigation was performed on the original ash and leached solid residues. The largest amounts of Co, Cu, Pb, and Zn were leached at pH 5, generally with the lowest concentrations between pH 9 and 11 and slightly increased concentrations at pH 12. For most elements, the released concentrations were very similar after 48 h and 168 h, indicating near-equilibrium conditions in the system. Calcite, clinopyroxenes, quartz and amorphous phases predominated in the fly ash. Various metal sulphides, alloys and the presence of Cu, Co and Zn in silicates and glass were detected using SEM/EDS and/or TEM/EDS. The leaching of metals was mainly due to dissolution of metallic particles. Partial dissolution of silicate and glass fractions was assumed to significantly influence the release of Ca, Mg, Fe, K, Al, and Si as well as Cu, Co and Zn. Illite was suggested by Orchestra to control the leaching of major elements, whereas Co and Zn were controlled by CoO and zincite respectively. Sorption of metals on hydrous ferric oxides was assumed to be important, especially for the release of Pb and Cu. There is a high risk of Co, Cu, Pb, and Zn mobility in acidic soils around the smelter, therefore potential local options for stabilisation of fly ash were evaluated using the PHREEQC code.

Differences in the total and bioaccessible concentrations of As and metals (Co, Cu, Pb, Zn) in topsoils (n=107) from the mining and smelting areas in the Zambian Copperbelt were evaluated. The mean total concentrations of metals and As in topsoils were generally 2-7 times higher in the smelting area, indicating significantly higher effect of smelter dust fallout on the degree of topsoil contamination. The contaminant bioaccessibility was tested by an US EPA-adopted in vitro method using a gastric fluid containing a 0.4 M solution of glycine adjusted to pH 1.5 by HCl. Higher bioaccessibilities in the smelter area were observed for As and Pb, attaining 100% of the total metal/metalloid concentration. The maximum bioaccessibilities of As and Pb in the mining area were 84% and 81% respectively. The ranges, mean and median bioaccessibilities of Co (maximum 58-65%), Cu (max. 80-83%), and Zn (max. 79-83%) were similar for the two areas. The obtained data indicate that a severe health risk related to topsoil ingestion should be taken into account, especially in smelting areas., Differences in the total and bioaccessible concentrations of As and metals (Co, Cu, Pb, Zn) in topsoils (n=107) from the mining and smelting areas in the Zambian Copperbelt were evaluated. The mean total concentrations of metals and As in topsoils were generally 2-7 times higher in the smelting area, indicating significantly higher effect of smelter dust fallout on the degree of topsoil contamination. The contaminant bioaccessibility was tested by an US EPA-adopted in vitro method using a gastric fluid containing a 0.4 M solution of glycine adjusted to pH 1.5 by HCl. Higher bioaccessibilities in the smelter area were observed for As and Pb, attaining 100% of the total metal/metalloid concentration. The maximum bioaccessibilities of As and Pb in the mining area were 84% and 81% respectively. The ranges, mean and median bioaccessibilities of Co (maximum 58-65%), Cu (max. 80-83%), and Zn (max. 79-83%) were similar for the two areas. The obtained data indicate that a severe health risk related to topsoil ingestion should be taken into account, especially in smelting areas.