SciCombinator

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Concept: Smelting

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Present day lead pollution is an environmental hazard of global proportions. A correct determination of natural lead levels is very important in order to evaluate anthropogenic lead contributions. In this paper, the anthropogenic signature of early metallurgy in Southern Iberia during the Holocene, more specifically during the Late Prehistory, was assessed by mean of a multiproxy approach: comparison of atmospheric lead pollution, fire regimes, deforestation, mass sediment transport, and archeological data. Although the onset of metallurgy in Southern Iberia is a matter of controversy, here we show the oldest lead pollution record from Western Europe in a continuous paleoenvironmental sequence, which suggests clear lead pollution caused by metallurgical activities since ~3900cal BP (Early Bronze Age). This lead pollution was especially important during Late Bronze and Early Iron ages. At the same time, since ~4000cal BP, an increase in fire activity is observed in this area, which is also coupled with deforestation and increased erosion rates. This study also shows that the lead pollution record locally reached near present-day values many times in the past, suggesting intensive use and manipulation of lead during those periods in this area.

Concepts: Copper, Erosion, Tin, Neolithic, Prehistory, Bronze Age, Smelting, Iron Age

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The Flin Flon, Manitoba copper smelter was Canada’s largest point source of mercury emissions until its closure in 2010 after ~80 years of operation. The objective of this study was to understand the variables controlling the local ground-level air mercury concentrations before and after this major point source reduction. Total gaseous mercury (TGM) in air, mercury in precipitation, and other ancillary meteorological and air quality parameters were measured pre and post-smelter closure, and mercury speciation measurements in air were collected post-closure. The results showed that TGM was significantly elevated during the time period when the smelter operated (4.1 ± 3.7 ng m-3), decreased only 20% during the year following its closure, and remained ~2-fold above background levels. Similar trends were observed for mercury concentrations in precipitation. Several lines of evidence indicated that while smelter stack emissions would occasionally mix down to the surface resulting in large spikes in TGM concentrations (up to 61 ng m-3), the largest contributor to elevated TGM concentrations before and after smelter closure was from surface-air fluxes from mercury-enriched soils and/or tailings. These findings highlight the ability of legacy mercury, deposited to local landscapes over decades from industrial activities, to significantly affect local air concentrations via emissions/re-emissions.

Concepts: Measurement, Precipitation, Atmosphere, Meteorology, C, Furnace, Smelting, Flin Flon

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Globally, billions of individuals wash their hair in water, which acts as an exogenous metal source. Many studies which measure the metal levels found on human hair specifically aim to remove exogenous materials prior to analysis. While this is needed when using hair analysis to probe the impact of the local environment on endogenous metal levels, it’s not relevant for understanding exactly what is on hair as a result of contact with its daily environment. Understanding these levels are important, as the presence of redox active metals, such as copper and iron, can impact fibre health, either due to UV irradiation, or during the hair colouring process. A global hair sampling study of over 300 individuals from nine countries has been performed, and the combined endogenous and exogenous metals analysed. The levels measured vary widely, even within the narrow geography of each hair sampling location. The levels of calcium, magnesium, copper and iron were not correlated, and within each location there are expected to be individuals with high metal levels. Levels increased from hair root to tip for calcium, magnesium and copper, attributed to hair’s contact with the environment showing the impact of exogenous metals in the overall levels on hair. Levels of redox metals were comparable between individuals who coloured or did not colour their hair, although water hardness ions were statistically significantly higher for hair colouring individuals. Individuals who perceived their hair health as poor had higher metal levels on their hair. Controlling metals on hair, either by preventing their binding during environmental contact, or through controlling their ability to cause hair damage, should lead to improved consumer perceived hair health. © 2013 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Concepts: Iron, Hydrogen, Calcium, Chemical element, Aluminium, Metal, Electrolysis, Smelting

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Lead (Pb) concentrations and isotopic compositions from soils, dusts and aerosols from public land and residential lots adjacent to the copper and Pb mine and smelter at Mount Isa, Australia, were examined to understand the sources and risks of environmental Pb exposure. Urban soil samples contain elevated Pb concentrations (mean 1560 mg/kg), of which 45-85% of the Pb is bioaccessible. The Pb isotopic composition of surface soils (0-2 cm), aerosols and dusts ((206)Pb/(207)Pb, (208)Pb/(207)Pb range: 1.049, 2.322-1.069, 2.345) are dominated by Pb derived from the Mount Isa Pb-zinc ore bodies. Underlying soil horizons (10-20 cm) have distinctly different Pb isotopic compositions ((206)Pb/(207)Pb, (208)Pb/(207)Pb range: 1.093, 2.354-1.212, 2.495). Surface soil-, dust- and aerosol-Pb are derived predominantly from smelter emissions and fugitive mining sources and not from in situ weathered bedrock. Remediation strategies should target legacy and ongoing sources of environmental Pb to mitigate the problem of Pb exposure at Mount Isa.

Concepts: Iron, Soil, Aluminium, Zinc, Copper, Lead, Charcoal, Smelting

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Washing and wet mopping is often advocated as a remedial treatment to limit exposure to lead dust. Here, surface and pre- and post-play wipes were measured to ascertain dust metal exposures (arsenic, cadmium, copper, lead and zinc) following play routines at four playgrounds in the smelter city of Port Pirie, South Australia, which are washed regularly. Although post-play hand wipe metals were 55.9% (95% CI: -0.78, -0.34) lower on wash days, loadings increased ∼5.1% (95% CI: 1.2, 11.7) per hour after washing. Despite washing, post-play hand lead exceeded a conservative value of 800 μg/m(2) within 24 h or sooner, with loadings increasing in proximity to the smelter. Post-play lead loadings were always >1000 μg/m(2) at the playground closest to smelter. Playground washing results in short-lived exposure reduction and effective treatment requires elimination of smelter emissions.

Concepts: Aluminium, Metal, Zinc, Copper, Silver, Heavy metal music, Smelting, Washing

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The disposal of slag generated by the steel industry can have negative consequences upon the surrounding aquatic environment by the generation of high pH waters, leaching of potentially problematic trace metals, and rapid rates of calcite precipitation which smother benthic habitats. A 36-year dataset was collated from the long-term ambient monitoring of physicochemical parameters and elemental concentrations of samples from two steel slag leachate-affected watercourses in northern England. Waters were typified by elevated pH (>10), high alkalinity, and were rich in dissolved metals (e.g. calcium (Ca), aluminium (Al), and zinc (Zn)). Long-term trend analysis was performed upon pH, alkalinity, and Ca concentration which, in addition to Ca flux calculations, were used to highlight the longevity of pollution arising as a result of the dumping and subsequent leaching of steel slags. Declines in calcium and alkalinity have been modest over the monitoring period and not accompanied by significant declines in water pH. If the monotonic trends of decline in alkalinity and calcium continue in the largest of the receiving streams, it will be in the region of 50-80 years before calcite precipitation would be expected to be close to baseline levels, where ecological impacts would be negligible.

Concepts: Iron, Water, Calcium, Aluminium, Zinc, Base, Corrosion, Smelting

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The mining and use of copper by prehistoric people on Michigan’s Keweenaw Peninsula is one of the oldest examples of metalworking. We analyzed the concentration of lead, titanium, magnesium, iron, and organic matter in sediment cores recovered from three lakes located near mine pits to investigate the timing, location, and magnitude of ancient copper mining pollution. Lead concentrations were normalized to lithogenic metals and organic matter to account for processes that can influence natural (or background) lead delivery. Nearly simultaneous lead enrichments occurred at Lake Manganese and Copper Falls Lake ~8000 and 7000 yr BP, indicating that copper extraction occurred concurrently in at least two locations on the peninsula. The poor temporal coherence among the lead enrichments from ~6300 to 5000 yr BP at each lake suggests that the focus of copper mining and annealing shifted through time. In sediment younger that ~5000 yr BP, lead concentrations remain at background levels at all three lakes, excluding historic lead increases starting ~150 yr BP. Our work demonstrates that lead emissions associated with both the historic and Old Copper Complex tradition are detectable and can be used to determine the temporal and geographic pattern of metal pollution.

Concepts: Iron, Lake, Eutrophication, Sediment, Metal, Copper, Bronze Age, Smelting

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Lead and cadmium are harmful heavy metals that are used for a variety of occupational purposes. Considering their potentially hazardous effects on health, studies on the association between exposure to these two heavy metals and health disorders have been actively conducted. This study aimed to determine the association between blood lead and cadmium levels and blood pressure in workers exposed to lead and cadmium in a smelter.

Concepts: Iron, Metal, Copper, Lead, Heavy metal music, Heavy metal, Smelting, Slag

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The recycling and recovery of valuable metals from waste materials is one of the key issues in maintaining the sustainability of base and rare metals. Especially WEEE (Waste Electric and Electronic Equipment) can be considered as a high potential resource for a number of valuable and critical metals like gallium, germanium and indium. During the mechanical processing of WEEE, these metals are primary separated into the non-ferrous scrap fractions, including copper fraction. As a consequence, the behavior of these valuable metals and the possibility of their recycling in secondary copper smelting are of great interest. This study experimentally investigates the distribution behavior of indium, gallium, germanium and tin between metallic copper and lime-free / lime-containing alumina iron silicate slags (L(Cu/s)[Me] = [Me]Copper/(Me)Slag), as well as between solid Al-Fe spinel and slags (L(sp/s)[Me] = {Me}spinel/(Me)slag). Moreover, the copper-slag-spinel equilibrium systems are examined. The experiments were executed simulating high alumina-bearing copper scrap smelting in typical black copper smelting conditions of pO2 = 10(-10)-10(-5) atm (1 atm = 1.01325 × 10(5) Pa) and T = 1300 °C. The experimental technique employed utilized a highly advanced equilibration-rapid quenching method followed by Electron Probe Micro-Analysis (EPMA). The results show that tin and indium can be efficiently recovered into the copper phase in reducing process conditions (pO2 below 10(-7) atm), whereas gallium dissolved preferentially into the solid spinel phase in all conditions examined. Gallium dissolution into slag and spinel was found to occur as GaO1.5, whereas indium in spinel was determined to be as InO1.5. In addition, germanium was seen to distribute preferentially into the copper phase with L(Cu/s)[Ge] = 2-4, although its concentrations in all phases present were relatively low. Thus, the main route for germanium can be considered to be vaporization.

Concepts: Iron, Aluminium, Metal, Copper, Germanium, Tin, Gallium, Smelting

0

Optimal operation of an industrial blast furnace (BF) ironmaking process largely depends on a reliable measurement of molten iron quality (MIQ) indices, which are not feasible using the conventional sensors. This paper proposes a novel data-driven robust modeling method for the online estimation and control of MIQ indices. First, a nonlinear autoregressive exogenous (NARX) model is constructed for the MIQ indices to completely capture the nonlinear dynamics of the BF process. Then, considering that the standard least-squares support vector regression (LS-SVR) cannot directly cope with the multioutput problem, a multitask transfer learning is proposed to design a novel multioutput LS-SVR (M-LS-SVR) for the learning of the NARX model. Furthermore, a novel M-estimator is proposed to reduce the interference of outliers and improve the robustness of the M-LS-SVR model. Since the weights of different outlier data are properly given by the weight function, their corresponding contributions on modeling can properly be distinguished, thus a robust modeling result can be achieved. Finally, a novel multiobjective evaluation index on the modeling performance is developed by comprehensively considering the root-mean-square error of modeling and the correlation coefficient on trend fitting, based on which the nondominated sorting genetic algorithm II is used to globally optimize the model parameters. Both experiments using industrial data and industrial applications illustrate that the proposed method can eliminate the adverse effect caused by the fluctuation of data in BF process efficiently. This indicates its stronger robustness and higher accuracy. Moreover, control testing shows that the developed model can be well applied to realize data-driven control of the BF process.

Concepts: Regression analysis, Iron, Industrial Revolution, Control theory, Robust statistics, Blast furnace, Smelting, Outlier