The Experts below are selected from a list of 10755 Experts worldwide ranked by ideXlab platform
James B Metson - One of the best experts on this subject based on the ideXlab platform.
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adsorptive capacity and evolution of the pore structure of alumina on reaction with gaseous hydrogen fluoride
Langmuir, 2015Co-Authors: Grant J Mcintosh, Gordon E K Agbenyegah, Margaret Hyland, James B MetsonAbstract:Brunauer–Emmet–Teller (BET) specific surface areas are generally used to gauge the propensity of uptake on adsorbents, with less attention paid to kinetic considerations. We explore the importance of such parameters by modeling the pore size distributions of Smelter grade aluminas following HF adsorption, an industrially important process in gas cleaning at aluminum Smelters. The pore size distributions of industrially fluorinated aluminas, and those contacted with HF in controlled laboratory trials, are reconstructed from the pore structure of the untreated materials when filtered through different models of adsorption. These studies demonstrate the presence of three distinct families of pores: those with uninhibited HF uptake, kinetically limited porosity, and pores that are surface blocked after negligible scrubbing. The surface areas of the inaccessible and blocked pores will overinflate estimates of the adsorption capacity of the adsorbate. We also demonstrate, contrary to conventional understanding,...
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adsorptive capacity and evolution of the pore structure of alumina on reaction with gaseous hydrogen fluoride
Langmuir, 2015Co-Authors: Grant J Mcintosh, Gordon E K Agbenyegah, Margaret Hyland, James B MetsonAbstract:Brunauer-Emmet-Teller (BET) specific surface areas are generally used to gauge the propensity of uptake on adsorbents, with less attention paid to kinetic considerations. We explore the importance of such parameters by modeling the pore size distributions of Smelter grade aluminas following HF adsorption, an industrially important process in gas cleaning at aluminum Smelters. The pore size distributions of industrially fluorinated aluminas, and those contacted with HF in controlled laboratory trials, are reconstructed from the pore structure of the untreated materials when filtered through different models of adsorption. These studies demonstrate the presence of three distinct families of pores: those with uninhibited HF uptake, kinetically limited porosity, and pores that are surface blocked after negligible scrubbing. The surface areas of the inaccessible and blocked pores will overinflate estimates of the adsorption capacity of the adsorbate. We also demonstrate, contrary to conventional understanding, that porosity changes are attributed not to monolayer uptake but more reasonably to pore length attenuation. The model assumes nothing specific regarding the Al2O3-HF system and is therefore likely general to adsorbate/adsorbent phenomena.
Michael Rabinowitz - One of the best experts on this subject based on the ideXlab platform.
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lead isotopes in soils near five historic american lead Smelters and refineries
Science of The Total Environment, 2005Co-Authors: Michael RabinowitzAbstract:This survey of soil lead in the vicinity of old industrial sites examines how the stable isotope patterns vary among the sites according to the sources of the lead ore processed at each site. Lead Smelters and refineries, which closed down decades ago, are the basis of this investigation. Samples were taken from near five old factory sites in Collinsville and Alton (Illinois), Ponderay (Idaho), East Chicago (Indiana) and Omaha (Nebraska). Historical records were searched for accounts of the sources of the lead. Lead concentrations were measured by atomic absorption flame spectrophotometry, and stable isotopic analysis was done by plasma ionization mass spectrometry. At every site visited, remnants of the old factories, in terms of soil lead pollution, could be found. In spite of potential complications of varying Smelter feedstock sourced from mines of different geological age, it was possible to match the isotopic patterns in the soils with the documented sources of the ores. The Collinsville and Alton sites resembled Missouri lead. The Ponderay value was higher than major Bunker Hill, Idaho deposits, but closer to the minor, nearby Oreille County, Washington ores. Mostly Utah ore was used in East Chicago. The Omaha soil reflects lead from Mexico, Colorado and Montana.
Mark R Cullen - One of the best experts on this subject based on the ideXlab platform.
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occupational exposure to pm2 5 and incidence of ischemic heart disease longitudinal targeted minimum loss based estimation
Epidemiology, 2015Co-Authors: Daniel M Brown, Mark R Cullen, Maya L Petersen, Sadie Costello, Elizabeth M Noth, Katherine Hammond, Mark J Van Der Laan, Ellen A EisenAbstract:BACKGROUND: We investigated the incidence of ischemic heart disease (IHD) in relation to accumulated exposure to particulate matter (PM) in a cohort of aluminum workers. We adjusted for time varying confounding characteristic of the healthy worker survivor effect, using a recently introduced method for the estimation of causal target parameters. METHODS: Applying longitudinal targeted minimum loss-based estimation, we estimated the difference in marginal cumulative risk of IHD in the cohort comparing counterfactual outcomes if always exposed above to always exposed below a PM2.5 exposure cut-off. Analyses were stratified by sub-cohort employed in either Smelters or fabrication facilities. We selected two exposure cut-offs a priori, at the median and 10th percentile in each sub-cohort. RESULTS: In Smelters, the estimated IHD risk difference after 15 years of accumulating PM2.5 exposure during follow-up was 2.9% (0.6%, 5.1%) using the 10th percentile cut-off of 0.10 mg/m. For fabrication workers, the difference was 2.5% (0.8%, 4.1%) at the 10th percentile of 0.06 mg/m. Using the median exposure cut-off, results were similar in direction but smaller in size. We present marginal incidence curves describing the cumulative risk of IHD over the course of follow-up for each sub-cohort under each intervention regimen. CONCLUSIONS: The accumulation of exposure to PM2.5 appears to result in higher risks of IHD in both aluminum Smelter and fabrication workers. This represents the first longitudinal application of targeted minimum loss-based estimation, a method for generating doubly robust semi-parametric efficient substitution estimators of causal parameters, in the fields of occupational and environmental epidemiology.
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acoustic neuroma potential risk factors and audiometric surveillance in the aluminium industry
Occupational and Environmental Medicine, 2014Co-Authors: Oyebode A Taiwo, Deron Galusha, Baylah Tessiersherman, Sharon R Kirsche, Linda F Cantley, Martin D Slade, Mark R Cullen, Michael A DonoghueAbstract:Objectives To look for an association between acoustic neuroma (AN) and participation in a hearing conservation programme (HCP) and also for an association between AN and possible occupational risk factors in the aluminium industry. Methods We conducted a case–control analysis of a population of US aluminium production workers in 8 Smelters and 43 other plants. Using insurance claims data, 97 cases of AN were identified between 1996 and 2009. Each was matched with four controls. Covariates included participation in a HCP, working in an aluminium Smelter, working in an electrical job and hearing loss. Results In the bivariate analyses, covariates associated with AN were participation in the HCP (OR=1.72; 95% CI 1.09 to 2.69) and Smelter work (OR=1.88; 95% CI 1.06 to 3.36). Electrical work was not significant (OR=1.60; 95% CI 0.65 to 3.94). Owing to high participation in the HCP in Smelters, multivariate subanalyses were required. In the multivariate analyses, participation in the HCP was the only statistically significant risk factor for AN. In the multivariate analysis restricted to employees not working in a Smelter, the OR was 1.81 (95% CI 1.04 to 3.17). Hearing loss, an indirect measure of in-ear noise dose, was not predictive of AN. Conclusions Our results suggest the incidental detection of previously undiagnosed tumours in workers who participated in the company-sponsored HCP. The increased medical surveillance among this population of workers most likely introduced detection bias, leading to the identification of AN cases that would have otherwise remained undetected.
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incident ischemic heart disease and recent occupational exposure to particulate matter in an aluminum cohort
Journal of Exposure Science and Environmental Epidemiology, 2014Co-Authors: Sadie Costello, Baylah Tessiersherman, Linda F Cantley, Martin D Slade, Daniel M Brown, Elizabeth M Noth, Ellen A Eisen, Katharine S Hammond, Mark R CullenAbstract:Fine particulate matter (PM2.5) in air pollution, primarily from combustion sources, is recognized as an important risk factor for cardiovascular events but studies of workplace PM2.5 exposure are rare. We conducted a prospective study of exposure to PM2.5 and incidence of ischemic heart disease (IHD) in a cohort of 11,966 US aluminum workers. Incident IHD was identified from medical claims data from 1998 to 2008. Quantitative metrics were developed for recent exposure (within the last year) and cumulative exposure; however, we emphasize recent exposure in the absence of interpretable work histories before follow-up. IHD was modestly associated with recent PM2.5 overall. In analysis restricted to recent exposures estimated with the highest confidence, the hazard ratio (HR) increased to 1.78 (95% CI: 1.02, 3.11) in the second quartile and remained elevated. When the analysis was stratified by work process, the HR rose monotonically to 1.5 in both Smelter and fabrication facilities, though exposure was almost an order of magnitude higher in Smelters. The differential exposure–response may be due to differences in exposure composition or healthy worker survivor effect. These results are consistent with the air pollution and cigarette smoke literature; recent exposure to PM2.5 in the workplace appears to increase the risk of IHD incidence.
Vojtěch Ettler - One of the best experts on this subject based on the ideXlab platform.
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transformation of arsenic rich copper Smelter flue dust in contrasting soils a 2 year field experiment
Environmental Pollution, 2018Co-Authors: Alice Jarosikova, Vojtěch Ettler, Martin Mihaljevic, Adam Culka, Vit Penižek, Tomas Matousek, Petr DrahotaAbstract:Abstract Dust emissions from copper Smelters processing arsenic-bearing ores represent a risk to soil environments due to the high levels of As and other inorganic contaminants. Using an in situ experiment in four different forest and grassland soils (pH 3.2–8.0) we studied the transformation of As-rich (>50 wt% As) copper Smelter dust over 24 months. Double polyamide bags with 1 g of flue dust were buried at different depths in soil pits and in 6-month intervals; then those bags, surrounding soil columns, and soil pore waters were collected and analysed. Dust dissolution was relatively fast during the first 6 months (5-34%), and mass losses attained 52% after 24 months. The key driving forces affecting dust dissolution were not only pH, but also the water percolation/retention in individual soils. Primary arsenolite (As2O3) dissolution was responsible for high As release from the dust (to 72%) and substantial increase of As in the soil (to a 56 × increase; to 1500 mg kg−1). Despite high arsenolite solubility, this phase persisted in the dust after 2 years of exposure. Mineralogical investigation indicated that mimetite [Pb5(AsO4)3(Cl,OH)], unidentified complex Ca-Pb-Fe-Zn arsenates, and Fe oxyhydroxides partly controlled the mobility of As and other metal(loid)s. Compared to As, other less abundant contaminants (Bi, Cu, Pb, Sb, Zn) were released into the soil to a lesser extent (8-40% of total). The relatively high mobility of As in the soil can be seen from decreases of bulk As concentrations after spring snowmelt, high water-extractable fractions with up to ∼50% of As(III) in extracts, and high As concentrations in soil pore waters. Results indicate that efficient controls of emissions from copper Smelters and flue dust disposal sites are needed to prevent extensive contamination of nearby soils by persistent As.
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soil contamination near non ferrous metal Smelters a review
Applied Geochemistry, 2016Co-Authors: Vojtěch EttlerAbstract:This review summarizes over 160 studies focused on soil contamination near non-ferrous metal Smelters. The methods of these investigations were examined with an emphasis on the combinations of traditional (geo)chemical approaches with various mineralogical and metal isotope techniques that are particularly helpful for depicting the fate of Smelter-derived contamination in the soil. Differences in the distributions and binding of metal(loid)s in Smelter-affected soils from temperate and (sub)tropical climatic zones indicate the greater vulnerability of the latter. Prevailing wind direction is a key factor affecting the dispersion of Smelter emissions and their subsequent deposition into the soils, with greater importance found especially in arid areas. Whereas the greatest contamination is generally observed in the surface soil layers, downward migration of metal(loid)s in the soil profiles has been documented at numerous sites. Contamination of Smelter soils significantly affects both plants and soil organisms, but suitable remediation techniques (such as chemical stabilization of soils by amendments) can be used for reducing the bioavailability of contaminants.
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trace elements and the lead isotopic record in marula sclerocarya birrea tree rings and soils near the tsumeb Smelter namibia
Water Air and Soil Pollution, 2015Co-Authors: Martin Mihaljevic, Vojtěch Ettler, Vit Penižek, Ales Vaněk, Miroslav Svoboda, Bohdan Křibek, Ondra Sracek, Benjamin Mapani, Akalemwa Fred KamonaAbstract:The contents of As, Cu, Cd, Pb, Mn, along with the Pb isotopic ratios 206Pb/207Pb and 208Pb/206Pb were studied in both soils and tree rings of the marula tree (Sclerocarya birrea) in the vicinity of the Tsumeb deposit (Namibia). Amounts of all the studied metals and As are higher in the immediate vicinity of the Tsumeb Cu-Pb Smelter in the soil. The tree rings also have their maximum content of all the studied substances in the vicinity of the Smelter (with the exception of Pb). At a more distant site, the maximum concentration of Pb in the soils was 29.8 mg/kg, while the content in the soil in the vicinity of the Smelter was as much as 8,174 mg/kg. In the vicinity of the Smelter, the maximum Pb content in the tree rings reaches a value of 5.7 mg/kg, compared to a more distant site, where the contents are as high as 9.2 mg/kg. The lower Pb content in the trees on contaminated soil indicates that the composition of the xylem determines the above-ground uptake, rather than the root uptake. Similarly, the above-ground uptake is documented by the isotopic composition of Pb at the distant location, where the tree rings have different contents of Pb isotopes compared to in the soil. The As, Cd, Cu, Pb, and Zn contents are highest in the tree rings from the 1950s (and older), along with those from the 1990s, while the Mn contents were highest in those from the 1960s and 1990s. The contaminant peaks in the 1950s and 1960s could be associated with the roasting of sulfidic ores, while the peak values in the 1990s could have been caused by the start of Cu slag reprocessing in the late 1980s, and culmination of works at the Smelter prior to the closing of the mine. The tree rings of the marula tree were found to be a suitable archive for above-ground pollution close to Cu and Pb Smelters.
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antimony mobility in lead Smelter polluted soils
Geoderma, 2010Co-Authors: Vojtěch Ettler, Martin Mihaljevic, Vaclav Tejnecký, Ondřej Sebek, Milan Zuna, Ales VaněkAbstract:Emissions from primary and secondary lead (Pb) Smelters are responsible for high concentrations of metallic contaminants (Pb, Cd and Zn) in soils. However, less attention has been paid to volatile metalloids, such as antimony (Sb), which accompanies Pb smelting activities. This paper is focused on geochemistry of Sb in the forest and agricultural soils in the vicinity of the Přibram Pb Smelter (Czech Republic), with emphasis on Sb distribution, chemical fractionation and comparison with the behaviour of another toxic metalloid, arsenic (As). Forest soils were enriched in Sb (4.86–2058 mg kg− 1, mean: 379 mg kg− 1, median: 155 mg kg− 1) with the highest concentrations in the organic horizons. Arsenic was found in significantly lower concentrations in forest soils (9.16–447 mg kg− 1, mean: 127 mg kg− 1, median: 82.9 mg kg− 1). High concentrations of metalloids in forest soils are related to higher interception of Smelter emissions by tree canopies. The Sb/As concentrations ratios ranged between 4.6 and 16.4 in the organic soil horizons, which is in agreement with (i) higher Sb deposition between ∼ 1890 and the 1970s as recorded by 210-Pb dated peat cores from the vicinity of the Smelter and (ii) rare historical analytical data on processed concentrates and dust from the Smelter flue-gas cleaning system. In contrast to organic horizons of forest soils, the concentrations of the two metalloids are rather similar in agricultural soils and in mineral horizons of the forest soils. Antimony concentrations in agricultural soils were in the range 3.12–131 mg kg− 1 (mean: 39.3 mg kg− 1, median: 23.8 mg kg− 1), whereas As concentrations were in the range 4.33–154 mg kg− 1 (mean: 60.3 mg kg− 1, median: 42.5 mg kg− 1). Factor analysis showed that Sb and As are statistically correlated to oxalate-extractable Fe, corresponding to amorphous or less crystalline Fe-oxides. The 5-step sequential extraction procedure (SEP), which was originally designed for As, and revised BCR SEP were applied to chemically fractionate Sb and As in the most polluted soil profiles. In forest soils, Sb was mostly bound in residual fraction with “mobile” concentrations in the range of 0.6–4% of the total Sb content. In contrast, As was significantly more mobile (1.2–22% of the total content in the “mobile” fractions) with dominant binding to Fe-oxides (up to 57% of total As content). In agricultural soils, Sb was again less “mobile” than As (1.4–5.9% and 0.34–12.1%, respectively of the total concentrations). Whereas Sb was mainly bound to the residual fraction and partly also in the reducible fraction (Fe-oxides), As was predominantly bound to Fe-oxides (up to 71% of the total As content). Good agreement was observed between the two SEP methods in determining the “mobile” concentrations of the metalloids (R2Sb = 0.9918 and R2As = 0.9104, p < 0.001). Despite probable similarities in the geochemical behaviour of these two metalloids in polluted soil systems, this study indicates that As is chemically more mobile than Sb.
Grant J Mcintosh - One of the best experts on this subject based on the ideXlab platform.
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adsorptive capacity and evolution of the pore structure of alumina on reaction with gaseous hydrogen fluoride
Langmuir, 2015Co-Authors: Grant J Mcintosh, Gordon E K Agbenyegah, Margaret Hyland, James B MetsonAbstract:Brunauer–Emmet–Teller (BET) specific surface areas are generally used to gauge the propensity of uptake on adsorbents, with less attention paid to kinetic considerations. We explore the importance of such parameters by modeling the pore size distributions of Smelter grade aluminas following HF adsorption, an industrially important process in gas cleaning at aluminum Smelters. The pore size distributions of industrially fluorinated aluminas, and those contacted with HF in controlled laboratory trials, are reconstructed from the pore structure of the untreated materials when filtered through different models of adsorption. These studies demonstrate the presence of three distinct families of pores: those with uninhibited HF uptake, kinetically limited porosity, and pores that are surface blocked after negligible scrubbing. The surface areas of the inaccessible and blocked pores will overinflate estimates of the adsorption capacity of the adsorbate. We also demonstrate, contrary to conventional understanding,...
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adsorptive capacity and evolution of the pore structure of alumina on reaction with gaseous hydrogen fluoride
Langmuir, 2015Co-Authors: Grant J Mcintosh, Gordon E K Agbenyegah, Margaret Hyland, James B MetsonAbstract:Brunauer-Emmet-Teller (BET) specific surface areas are generally used to gauge the propensity of uptake on adsorbents, with less attention paid to kinetic considerations. We explore the importance of such parameters by modeling the pore size distributions of Smelter grade aluminas following HF adsorption, an industrially important process in gas cleaning at aluminum Smelters. The pore size distributions of industrially fluorinated aluminas, and those contacted with HF in controlled laboratory trials, are reconstructed from the pore structure of the untreated materials when filtered through different models of adsorption. These studies demonstrate the presence of three distinct families of pores: those with uninhibited HF uptake, kinetically limited porosity, and pores that are surface blocked after negligible scrubbing. The surface areas of the inaccessible and blocked pores will overinflate estimates of the adsorption capacity of the adsorbate. We also demonstrate, contrary to conventional understanding, that porosity changes are attributed not to monolayer uptake but more reasonably to pore length attenuation. The model assumes nothing specific regarding the Al2O3-HF system and is therefore likely general to adsorbate/adsorbent phenomena.
