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• Cd and Hg were the most polluted HMs in the study area. • ZZ3 and ZZ7 were the most polluted workshops and required priority control. • GIS, PMF, and APCS-MLR models were used to analyze the precise sources of HMs. • Cd and Hg were respectively derived from smelting process and atmospheric deposition. The abandoned smelters present a substantial pollution threat to the nearby soil and groundwater. In this study, 63 surface soil samples were collected from a zinc smelter to quantitatively describe the pollution characteristics, ecological risks, and source apportionment of heavy metal(loid)s (HMs). The results revealed that the average contents of Zn, Cd, Pb, As, and Hg were 0.4, 12.2, 3.3, 5.3, and 12.7 times higher than the risk screening values of the construction sites, respectively. Notably, the smelter was accumulated heavily with Cd and Hg, and the contribution of Cd (0.38) and Hg (0.53) to ecological risk was 91.58%. ZZ3 and ZZ7 were the most polluted workshops, accounting for 25.7% and 35.0% of the pollution load and ecological risk, respectively. The influence of soil parent materials on pollution was minor compared to various workshops within the smelter. Combined with PMF, APCS-MLR and GIS analysis, four sources of HMs were identified: P1(25.5%) and A3(18.4%) were atmospheric deposition from the electric defogging workshop and surface runoff from the smelter; P2(32.7%) and A2(20.9%) were surface runoff of As-Pb foul acid; P3(14.5%) and A4(49.8%) were atmospheric deposition from the leach slag drying workshop; P4(27.3%) and A1(10.8%) were the smelting process of zinc products. This paper described the distribution characteristics and specific sources of HMs in different process workshops, providing a new perspective for the precise remediation of the smelter by determining the priority control factors. [Display omitted] [ABSTRACT FROM AUTHOR]

Roaster furnace is a large-scale equipment in zinc smelting process, which plays an significant role in safety production and enviromental protection. An accurate digital twin of roaster furnace can help to explore the influence of control parameters and serve as a test platform to verify the effectiveness of control strategies. However, the traditional thermodynamics cannot be used for dynamic modeling, and inability to measure key data greatly affects the accuracy of kinetic modeling. Therefore, this paper establishes a novel digital twin of zinc roaster furnace based on knowledge-guided variable-mass thermodynamics. First, based on the integration of mechanism analysis for mass balance and energy balance, a dynamic modeling method is proposed. Then, particle swarm optimization (PSO) algorithm is introduced to optimize the parameters of conversion rates guided by knowledge. Finally, by connecting the dynamic model with distributed control system (DCS) through OPC communication protocol, a digital twin of roaster furnace is constructed. Extensive experiments show that the simulation results of the digital twin roughly agree with the actual industrial data under steady and dynamic working conditions, and the application of the digital twin on the performance analysis of control parameters and testing of control strategies can provide guidance for the optimal control of roaster furnace. [ABSTRACT FROM AUTHOR]

[Display omitted] • The oxidative pressure leaching process for treating ZnS concentrate was modeled. • The process simulation-based life cycle assessment method was used. • The environmental impacts of the oxidative pressure leaching process was studied. • Zn, Cd, Co, Ga, and Ge production exhibited lower environmental impacts. • Recommendations for the process to sustainable zinc production were given. Considering the increasing environmental consciousness and the imperative for sustainable development, conventional zinc smelting operations employing the roast-leaching-electrowinning process face growing environmental pressures. Consequently, the oxidative pressure leaching process has emerged as an alternative processing route. This study focuses on recovery of major metals from ZnS concentrate, building a comprehensive model to simulate the oxidative pressure leaching process. The process model built demonstrated that zinc, sulfur, indium, gallium, cadmium, cobalt, germanium, and copper could be recovered effectively, the main chemical inputs being sulfuric acid, oxygen, and lime, while zinc electrowinning constituting over 90 % of the total electricity consumption. The results were used to compile a life cycle inventory, culminating in a gate-to-gate assessment of the environmental impacts of the process. The global warming potential for the treatment of 1 t of ZnS concentrate is approximately 2,000 kg CO 2 eq. The primary environmental impacts in the process are from chemical inputs and electricity consumption. Based on these findings, recommendations for sustainable production practices are proposed. These include systematic recovery and reuse of electrolytic off-gas and roasting heat, greater utilization of renewable energy, enhanced iron removal processes, and exploration of alternative chemicals for Ga and Ge recovery. [ABSTRACT FROM AUTHOR]

The zinc smelting solution purification process regulates the oxidation-reduction reactions (characterized by the oxidation-reduction potential (ORP)) by controlling the amount of zinc powder added to remove the impurity ions. In order to ensure the optimal operation of the process, the target key technical indicators should be converted into the optimal setpoint of controlled variables (that is, ORP). Based on the mechanism knowledge, fuzzy rules, and preference-guided predictive optimization, a comprehensive setting method for the optimal setpoint of controlled variables under multi-variation inlet status is proposed. It includes a hybrid trend detection method for inlet status, a mechanism model under multiple operating modes, and a fuzzy correction method and a preference-guided predictive optimization method to deal with slight and violent fluctuations in the inlet status, respectively. The experimental results show that the proposed method can obtain the optimal setpoint of controlled variables and reduce zinc powder consumption by approximately 3.6%. • A comprehensive setting method for the optimal setpoint of controlled variables under multi-variation status is proposed. • A hybrid trend detection method is proposed to identify different inlet statuses of the solution purification process. • Based on the reaction kinetics and the reaction efficiency, a mechanism model under multiple operating modes is constructed. • An optimal setpoint correction method based on fuzzy rules is proposed to cope with slight changes in inlet status. • A preference-guided predictive optimization method is proposed to cope with violent changes or anomalies in inlet status. [ABSTRACT FROM AUTHOR]

• A method of selective microwave heating of mercury-containing solid waste was established. • The optimal process parameters and mercury metabolism kinetics of the mercury removal process were verified. • Microwave can reduce the activation energy of the reaction and thus increase the volatilization rate of mercury. During the production process of lead and zinc smelting, a highly hazardous solid waste is generated. This waste contains valuable metal resources such as mercury, selenium, and lead. Specifically, the waste contains high levels of mercury, making it a hazardous waste. Currently, the treatment processes for this mercury-containing solid waste have drawbacks, including the need for high temperatures and long heating times. A novel process using microwave external field enhancement for the removal of mercury was proposed. The study also determined the optimal process parameters and investigated the kinetics of mercury metabolism. The experimental results indicated that the mercury-containing group members were the main substances absorbing microwaves in the mercury-containing solid waste. In terms of optimal process parameters, a heating temperature of 600 °C, a reaction time of 30 min, an oxygen flow rate of 20 L/h, and a volatilization efficiency of mercury exceeding 99 % were achieved. The volatilization kinetics of mercury during heating of the mercury-containing solid waste followed a first-order reaction model. Furthermore, the activation energy for microwave mercury removal was found to be 6.06 kJ/mol lower than that for conventional mercury removal, with a value of 29.41 kJ/mol. This lower activation energy facilitated a higher mercury removal efficiency compared to conventional methods. The use of microwaves allows for the selective heating of the mercury-containing components in solid waste, resulting in an increased volatilization efficiency of mercury. By utilizing a microwave heating system, mercury is effectively recycled as high-mercury slag. This approach effectively addresses the environmental concerns associated with mercury-containing solid waste. [Display omitted] [ABSTRACT FROM AUTHOR]

The fusion of industrial artificial intelligence with the Industrial Internet of Things (IIoT) can attain a heightened level of process monitoring in modern manufacturing processes. In general, the state variables of industrial processes collected through the IIoT encompass not only continuous variables but also numerous discrete variables. Owing to potential coupling factors, these variables frequently exhibit strong correlations. However, most existing methods deal only with continuous variables, which results in breaking the integrity of the state information and being incompetent to extract the useful information carried by discrete variables. To effectively address the joint monitoring challenges of continuous and discrete variables under the IIoT framework, hybrid variable dictionary learning (HVDL) is proposed in this paper. Specifically, considering that the values of discrete variables are finite sets, a specific discrete dictionary is built for data reconstruction. Besides, in order to consider the correlation between continuous and discrete variables, the alignment of them in the time dimension is achieved by sharing labels. The HVDL method can judiciously learn data dictionaries to extract multifaceted valid features across diverse data types, free from prior assumptions on data distributions. Finally, extensive experiments are conducted to demonstrate the superiority of the proposed method, including a numerical simulation case, a closed-loop continuous stirred tank reactor benchmark, and a real zinc smelting roaster. Experimental results indicate that the proposed method can fully consider the correlation between continuous and discrete variables, thus it is conducive to identifying early anomalies and mismatch anomalies. [ABSTRACT FROM AUTHOR]

Arsenic-containing multi-metallic materials, are typical hazardous wastes generated in the process of tin recovery from zinc smelting leach slag, exhibit low resource utilization and pose a significant risk of environmental pollution. This research proposed a vacuum reduction roasting technique utilizing anthracite as the reducing agent to remove arsenic and reclaim tin from such materials, characterized by high arsenic levels (8∼wt%) and the presence of several valuable metals. The results indicated that the arsenate in these materials was transformed into As 2 O 3 , which has better volatility, while SnO 2 was converted to SnO and Sn. Moreover, under the optimal conditions of a roasting temperature of 750 °C, 10 % anthracite, and a roasting duration of 3 h, the arsenic removal efficiency reached 96.97 %, and the tin recovery rate was 84.48 %. Consequently, the arsenic concentration decreased to 0.53 %, and the tin concentration in the roasted product increased from 17.70 % to 31.41 %. The final product contained phases of arsenic and tin, including Sn, SnO 2 , and FeAs. Meanwhile, this study provides a promising solution for the green and efficient separation of tin and arsenic in typical arsenic-containing multi-metallic materials. • The evolution mechanisms of typical compositions Zn 3 (AsO 4) 2 , As 2 O 3 , As, SnO 2 , SnO, and Sn in arsenic-containing multi-metallic materials were investigated and discussed in detail. • Highly efficient arsenic removal (96.97 %) and green enrichment of tin in aresenic-containing multi-metallic materials. [ABSTRACT FROM AUTHOR]

• THg, MeHg and IHg in paired hair and fingernail samples from two typical mining areas showed positive correlation. • Fingernail samples can be another useful biomarker in application of assessing human Hg exposure. • Hair plays a more important role than fingernails in the excretion of Hg from human body. Effective biomarkers are necessary to better understand the human mercury (Hg) exposure levels. However, mismatched biomarker sampling method causes extra uncertainty in assessing the risk of Hg exposure. To compare the differences between hair and fingernail, and further understand the excretion rates of methylmercury (MeHg) and inorganic mercury (IHg) via hair and fingernails, the total mercury (THg), MeHg, and IHg concentrations in paired hair and fingernail samples were investigated through paired samples collected from two typical mining areas, Wanshan mercury mine area (WMMA) and Hezhang zinc smelting area (HZSA). The positive correlation in THg, MeHg, and IHg concentrations (p <0.01) between hair and fingernail samples indicated that those two biomarkers can be corrected in application of assessing human Hg exposure. Compared to fingernails, the hair was suggested to be a more sensitive biomarker as the concentration of THg, MeHg and IHg were 2 ∼ 4 times higher than those in fingernails. Furthermore, the amounts of THg, MeHg, and IHg excreted via hair were 70 ∼ 226 times higher than that excreted via fingernails, and the hair plays a more important role than fingernails in the excretion of Hg from human bodies. Present study therefore provides some new insights to better understand the fate of human assimilated Hg. [Display omitted] [ABSTRACT FROM AUTHOR]

Indium (In) has vital applications in solar photovoltaic technology and light-emitting diodes. However, the resource for In production is low. Zinc smelting is an important source of In, but the average In recovery rate is only 20%. The annual economic loss due to the loss of In is as high as USD 199.7 million. In this study, a high-sulphur hot filter residue (HFR) was processed via sodium-hydroxide (NaOH) hydrothermal treatment (NAHT). By varying the amount of NaOH and using the dissolution exotherm of NaOH, sulphur element (S0) in HFR was transferred to a liquid phase. Thus, In and other precious metals originally wrapped in S0 were enriched in the slag phase (TLR). The In grade in TLR was as high as 1700 g/t, and the recovery rate was 99%. In addition, 10.94 g/t gold, 125.81 g/t silver, 15.18% zinc and 22.27% iron were incidentally recovered. The wastewater produced in the process showed better effects than industrial Na 2 S in flotation processes. Thus, NAHT is an effective green recovery technique for recovering In and other precious metals from HFR. Further, the recovered In can yield an annual revenue of USD 1,122,170 for the plant. Therefore, the treatment of HFR plays an important role in zinc hydrometallurgical smelting plants. Green process diagram for recovering indium and other precious metal resources from high-sulphur hot filter residue (HFR) by using NaOH hydrothermal (NAHT) treatment [Display omitted] • Indium and other precious metals in high-sulphur hot filter residue were recovered by NaOH hydrothermal treatment. • Indium content in TLR was as high as 1700 g/t, and the recovery rate was 99.07%. • Gold, silver, zinc and iron were accidentally recovered from HFR at a rate greater than 90%. • No waste was produced in the process. • The recovered indium can bring annual revenue of USD1,122,170. [ABSTRACT FROM AUTHOR]

• A highly efficient reductive leaching process for zinc ferrite-based solid waste decomposition. • Highly efficient utilization ratio of zinc sulfide as a reductant. Zinc ferrite-based solid waste is a vital zinc and iron secondary source in view of the numerous zinc ferrite will be ineluctably produced and enters into slags or residues during zinc smelting process. In this study, a reductive leaching process with zinc sulfide powder was employed to decompose zinc ferrite from solid waste. The leaching efficiency of zinc and iron can reach 90.27 % and 81.96 %, respectively, while the process went to the 90th min at 90 ℃ under the conditions: sulfuric acid concentration of 500 g/L, liquid-to-solid ratio of 20 mL g−1, mass ratio of silver flotation tailings to zinc sulfide of 5/1, silver flotation tailings particle size of + 180–250 μm, rotary speed of 400 rpm. Then, this leaching process confirmed to shrinking core model and was conducted by surface chemical reaction after kinetics and thermodynamics investigations. Ultimately, according to various tested data, the corresponding reaction mechanism was speculated as: Fe3+ was reduced to Fe2+ by zinc sulfide and hydrogen sulfide which was the product of zinc sulfide with H+, resulting in potential reduction and H+ activity elevation, accelerating zinc dissolution eventually. Meanwhile, almost all zinc sulfide and hydrogen sulfide were oxidized to monomorphic sulfur by Fe3+ where the utilization ratio of zinc sulfide was 97.28 %. [ABSTRACT FROM AUTHOR]

Heavy metal pollution at an abandoned smelter pose a significant risk to environmental health. However, remediation strategies are constrained by inadequate knowledge of the polymetallic distribution, speciation patterns, and transformation factors at these sites. This study investigates the influence of soil minerals, heavy metal occurrence forms, and environmental factors on heavy metal migration behaviors and speciation transformations. X-ray diffraction analysis revealed that the minerals associated with heavy metals are mainly hematite, franklinite, sphalerite, and galena. Sequential extraction results suggest that lead and zinc are primarily present in the organic-sulfide fractions (F4) and residual form (F5) in the soil, accounting for over 70% of the total heavy metal content. Zinc displayed greater instability in carbonate-bound (16%) and exchangeable (2%) forms. The migration and diffusion patterns of heavy metals in the subsurface environment were visualized through the simulation of labile state heavy metals, demonstrating high congruence with groundwater pollution distribution patterns. The key environmental factors influencing heavy metal stable states (F4 and F5) were assessed by integrating random forest models and redundancy analysis. Primary factors facilitating Pb transformation into stable states were available phosphorus, clay content, depth, and soil organic matter. For Zn, the principal drivers were Mn oxides, soil organic matter, clay content, and inorganic sulfur ions. These findings enhance understanding of the distribution and transformation of heavy metal speciation and can provide valuable insights into controlling heavy metal pollution at non-ferrous smelting sites. [Display omitted] • The samples from the site reveal considerable heavy metal contamination due to zinc iron spinel, galena, sphalerite, hematite. • Pb and Zn in the soil exist primarily in the stable form, with the labile state closely aligns with groundwater contamination. • The zinc content contributes to its excessive presence in groundwater due to temporal and spatial accumulation. • Available phosphorus, Mn oxides, clay, depth, and soil organic matter facilitate the transformation of heavy metals into stable states. [ABSTRACT FROM AUTHOR]

Heavy metal(loid)s (HMs) in soils of Southwest China naturally have a high background and are superimposed with intensive anthropogenic activities, resulting in serious accumulation of HMs in regional agricultural soils, which poses threat to ecological security and agricultural product quality. The accumulation and source apportionment of HMs in agricultural soils are not only one of the focuses of global concern but also a challenging task worldwide. In the present study, a total of 395 topsoil samples (0-20 cm) and 19 deep soil samples (150-180 cm) were collected from typical artisanal zinc smelting regions in northwestern Guizhou Province, China to investigate the spatial distribution, accumulation and source apportionment of HMs (As, Cr, Cu, Hg, Ni, Pb, Cd and Zn) based on the combined approach of enrichment factor (EF), self-organizing map (SOM), geographical information system (GIS), and positive matrix factorization (PMF). The mean contents of As, Cr, Cu, Hg, Ni, Pb, Cd and Zn in agricultural soils all exceeded the corresponding local background values, and obvious enrichment of Cd was found in the studied topsoil, followed by Pb, Cu, and Zn. Combined with SOM and PMF analysis, five potential HMs sources were identified: Cd (74.58%), As (32.05%), Zn (30.57%), Hg (23.16%), and Pb (11.38%) were associated with artisanal Zn smelting activities; Cu (66.08%), Zn (18.12%), Ni (17.25%), Cd (16.95%), and Pb (10.08%) were mainly from agricultural activities; Pb (68.9%), Zn (25.73%), and As (22.64%) were mainly from traffic emissions and smelting-related activity sources; Hg (68.55%), As (45.31%), Cr (38.63%), and Ni (32.44%) were primarily from atmospheric deposition associated with industrial activities and coal combustion; and Cr (61.01%), Ni (44.52%), Zn (17.32%), Cu (16.11%), and Cd (8.39%) mainly originated from soil parent materials. The proportions of the five potential sources were 14.5%, 20.9%, 19.8%, 17.8%, and 27%, respectively. Anthropogenic sources accounted for the largest contribution (approximately 73%) to the soil HMs, especially the artisanal zinc smelting activities to Cd, Zn, As, Hg, and Pb, which was significantly higher than that of geological sources, suggesting that intense human activities produced a large amount of HMs enrichment in topsoil. The SOM clustering and source apportionment of soil HMs are of great significance for reducing HMs pollution sources, and can provide scientific guidance for pollution prevention and regional remediation of HMs in agricultural soils. [ABSTRACT FROM AUTHOR]

[Display omitted] Heavy metal(loid)s (HMs) in soils of Southwest China naturally have a high background and are superimposed with intensive anthropogenic activities, resulting in serious accumulation of HMs in regional agricultural soils, which poses threat to ecological security and agricultural product quality. The accumulation and source apportionment of HMs in agricultural soils are not only one of the focuses of global concern but also a challenging task worldwide. In the present study, a total of 395 topsoil samples (0–20 cm) and 19 deep soil samples (150–180 cm) were collected from typical artisanal zinc smelting regions in northwestern Guizhou Province, China to investigate the spatial distribution, accumulation and source apportionment of HMs (As, Cr, Cu, Hg, Ni, Pb, Cd and Zn) based on the combined approach of enrichment factor (EF), self-organizing map (SOM), geographical information system (GIS), and positive matrix factorization (PMF). The mean contents of As, Cr, Cu, Hg, Ni, Pb, Cd and Zn in agricultural soils all exceeded the corresponding local background values, and obvious enrichment of Cd was found in the studied topsoil, followed by Pb, Cu, and Zn. Combined with SOM and PMF analysis, five potential HMs sources were identified: Cd (74.58%), As (32.05%), Zn (30.57%), Hg (23.16%), and Pb (11.38%) were associated with artisanal Zn smelting activities; Cu (66.08%), Zn (18.12%), Ni (17.25%), Cd (16.95%), and Pb (10.08%) were mainly from agricultural activities; Pb (68.9%), Zn (25.73%), and As (22.64%) were mainly from traffic emissions and smelting-related activity sources; Hg (68.55%), As (45.31%), Cr (38.63%), and Ni (32.44%) were primarily from atmospheric deposition associated with industrial activities and coal combustion; and Cr (61.01%), Ni (44.52%), Zn (17.32%), Cu (16.11%), and Cd (8.39%) mainly originated from soil parent materials. The proportions of the five potential sources were 14.5%, 20.9%, 19.8%, 17.8%, and 27%, respectively. Anthropogenic sources accounted for the largest contribution (approximately 73%) to the soil HMs, especially the artisanal zinc smelting activities to Cd, Zn, As, Hg, and Pb, which was significantly higher than that of geological sources, suggesting that intense human activities produced a large amount of HMs enrichment in topsoil. The SOM clustering and source apportionment of soil HMs are of great significance for reducing HMs pollution sources, and can provide scientific guidance for pollution prevention and regional remediation of HMs in agricultural soils. [ABSTRACT FROM AUTHOR]

Iron slag, a byproduct of the wet zinc refining process, contains a substantial amount of valuable metals such as iron and zinc, making it highly valuable for comprehensive recovery and reuse. However, before recovery, the iron slag requires dehydration pretreatment. The water content in iron slag remains relatively high and difficult to remove even after pressure filtration, leading to extended drying times, reduced drying efficiency, and increased energy consumption. This study explores a novel ultrasonic pretreatment process for iron slag. Using the response surface methodology, we investigated the effects of ultrasonic power, ultrasonic time, liquid-to-solid ratio, and their interactions on the water content, capillary suction time (CST), and filtration resistance of the slag. Regression equations were established to predict the relationships between the water content, CST, filtration resistance, and the various factors. The optimal process parameters were determined as an ultrasonic power of 60 W, ultrasonic time of 22 s, and a liquid-to-solid ratio of 4:1. Under these conditions, the dehydration performance of the iron slag was optimal. The measured values closely matched the predicted values, demonstrating the reliability of the model and the feasibility of the optimized process. Our study of the mechanism of ultrasonic action on iron slag found that under the influence of ultrasonic waves, the particle size of the slag significantly decreased, and the particle morphology changed. Compared to conventional drying, the drying rate of the iron slag after ultrasonic pretreatment was accelerated, and the drying time was reduced. [ABSTRACT FROM AUTHOR]

Groundwater pollution is a recurrent problem in abandoned non-ferrous metal smelting sites, and its severity is influenced by topsoil contamination, hydrogeological characteristics, and hydrogeochemical conditions. In such unique areas, traditional methods for evaluating groundwater pollution risk are biased, as the long production history of these sites have led to highly polluted and heterogeneous soil and groundwater. Herein, based on a typical lead-zinc smelting site, As, Pb, Zn, Cd, Mn, and Ni were found to be the predominant heavy metal (loid)s in groundwater, with respective exceedance rates of 44.4%, 50.0%, 72.2%, 88.9%, 88.9%, and 61.1%. Combined with the groundwater pollution characteristics, the representative hydrogeochemical factors were screened out to optimize the following aquifer vulnerability evaluation using the AHP-DRASTICH method. A comprehensive evaluation model (DI-NCPI) for groundwater pollution risk was established by combining the DRASTICH index (DI) obtained after optimization and the Nemerow comprehensive contamination index (NCPI) of topsoil. The fit between DI-NCPI and groundwater heavy metal (loid) pollution index reached 0.956, which laterally confirms that the model has some reference value. In terms of distribution, the high-risk and very high-risk zones were mainly concentrated in the zinc smelting system, located in the southeastern and central-western parts of the site. These areas have relatively high levels of topsoil contamination and aquifer vulnerability and require focused attention in site remediation. This research highlights the importance of combining topsoil contamination and aquifer vulnerability to evaluate groundwater pollution risk in smelting areas. It provides a more targeted reference for groundwater remediation strategies in abandoned smelting sites, as well as severely polluted industrial areas. [Display omitted] • As, Pb, Zn, Cd, Mn, and Ni were the predominant heavy metal (loid)s in groundwater. • Propose a groundwater pollution risk evaluation model in abandoned smelting sites. • The fit of the evaluation results to the pollution status reached 0.956. • The evaluation model provides more targeted references for remediation strategies. [ABSTRACT FROM AUTHOR]

• EDXRF combined machine learning proposed rapid identify heavy metal contained waste. • Spectral mechanism with random forest model were analyzed and accuracy reached 100%. • Application in environmental management and pollution traceability were discussed. • It can become a new technical mean to identify genome of different industrial waste. To address the time-consuming identification and poor timeliness of environmental pollution tracing problems of traditional chemical detection methods for hazardous solid waste, a rapid identification and characterization methodology for hazardous waste containing heavy metals is established by using the EDXRF spectroscopy principle combined with an optical intelligent optimization algorithm. Two years of long-time serial optical spectrum information are collected from nine typical types of hazardous waste containing heavy metals produced in the zinc smelting process using EDXRFs, online analytical instruments installed on different process lines. Then, different machine learning models are applied to identify the key spectral factors that are first screened after noise reduction and standardization to pretreat all spectrum information data to distinguish different characteristics of each type of hazardous waste. Finally, the random forest model is selected and optimized to improve its identification accuracy. The results show that the spectral line signals corresponding to heavy metal elements such as Fe, Zn, Cu, Cd, and Ag in zinc smelting materials can be used as important factors to distinguish different types of zinc smelting solid waste. Because different smelting processes lead to different heavy metal contents in different types of zinc smelting hazardous waste, the optimized random forest model can be implemented to accurately identify and characterize nine typical types of hazardous waste containing heavy metals, and an accuracy rate of 100% is achieved. This method provides an efficient tool for the environmental management of hazardous waste and the rapid tracing of environmental risks in the future. Especially in tracking soil or surface water pollution caused by the illegal dumping of solid waste, the rapid identification and characterization of solid waste are of great significance for the quality supervision of regional ecological environments. [Display omitted] [ABSTRACT FROM AUTHOR]

Particulate organic matter (POM) significantly affects the distribution of heavy metals in contaminated soil. However, the effect of POM on the fate of heavy metals during in situ- aided phytostabilization of waste slag is unclear. The objective of this study was to investigate the distributions of heavy metals such as Cu, Pb, Zn, and Cd in the POM fractions at a zinc smelting waste slag site under in situ- aided phytostabilization after five years. The results showed that the litters and residues of four plants― Arundo donax, Broussonetia papyrifera , Cryptomeria fortunei , and Robinia pseudoacacia ―decomposed to form different POM size fractions. The percentage of the 0.05–0.25 mm POM size fraction was the highest, followed by the >1 mm and 0.5–1 mm POM size fractions, and that of the 0.25–0.5 mm POM size fraction was the lowest. The masses of POM derived from the four plants were in the following order: C. fortunei > B. papyrifera > A. donax > R. pseudoacacia. The contents, enrichment coefficients, and mass loads of heavy metals such as Cu, Pb, Zn, and Cd in the POM increased with decreasing POM size, and those in the 0.05–0.25 mm POM size fraction were the highest. The mass load of heavy metals in the POM occurred in the following order: Cu > Cd > Zn > Pb. The surfaces of the POM with coarser and smaller size fractions were smoother and rougher, respectively, and the smaller POM size fractions had larger specific surface areas. The main functional groups in the different POM size fractions were –COOH, –OH, C O, C C, C–H, Si–O, and –CH 3. The POM fractions played a significant role in determining the distribution of heavy metals in the revegetated waste slag. These findings have important implications for aided phytostabilization, which significantly influences the fate and speciation of heavy metals at the phytoremediation site. Image 10791 • POM fractions on heavy metal fate at a phytoremediation site was firstly studied. • Heavy metal enrichment in the POM fractions increased with decreasing POM size. • The 0.05–0.25 mm POM fractions had the highest adsorption capacity for metals. • The kinds of functional groups in the different POM size fractions were similar. Heavy metal distributions in different particulate organic matter size fractions significantly influenced the fate and speciation of heavy metals at a phytoremediation site. [ABSTRACT FROM AUTHOR]

• A germanium bearing secondary zinc oxide was evaluated mineralogically. • Germanium exists in zinc and lead bearing minerals dispersedly. • Leaching behavior of Ge was revealed by leaching tests and residue characterization. • The limiting reasons of Ge and Zn leaching rates were found out. • 99.7% of Ge and 99.4% of Zn could be leached in oxygen pressure leaching. To improve the sulfuric-acid leaching of germanium-bearing secondary zinc oxide, the occurrence states and sulfuric-acid leaching behavior of germanium in secondary zinc oxide were investigated experimentally via inductively coupled plasma optical emission spectrometry (ICP–OES), X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive spectroscopy (SEM–EDS), electron probe microanalysis (EPMA), and chemical phase analysis combined with leaching tests. The germanium-bearing secondary zinc oxide was produced via a fuming process of lead smelting slag and zinc leaching residue in a lead and zinc smelter. The results show that zincite, wurtzite, galena, and anglesite are the major minerals containing zinc and lead in the secondary zinc oxide. Further, these zinc- and lead-bearing materials contain germanium (without independent minerals). In the sulfuric-acid leaching process without oxidant, wurtzite and galena cannot be leached, which results in a loss of germanium. Anglesite, which exists originally in the secondary zinc oxide or was formed in the leaching process, contains a low amount of germanium and exhibits a loss of germanium in the residue. Moreover, the leaching efficiencies of germanium and zinc increased to 99.7% and 99.4% in the leaching process under oxygen pressure, respectively. [ABSTRACT FROM AUTHOR]

The city of Port Pirie in South Australia has been a world leading centre for lead and zinc smelting and processing since 1889 that continues to cause contamination of its environment and resident population. This study quantifies the effect of lead and SO 2 emissions from Nyrstar Port Pirie Pty Ltd's smelter on blood lead and respiratory health outcomes, respectively, and establishes what air quality values are required to better protect human health. Blood lead and emergency department presentation data collected by South Australia Health (SA Health) and lead in air and SO 2 data collected by the South Australian Environment Protection Authority (SAEPA) were obtained and analysed to quantify health outcomes due to smelter emissions in Port Pirie. Regression analysis was used to assess the relationship between the concentration of lead in air and children's blood lead levels between the years of available data: 2003 to 2017. Ambient SO 2 concentrations (SAEPA) measured continuously between 2008 and 2018 were 24-hour averaged and compared to daily local emergency department respiratory presentation rates (available from July 2012 to October 2018). Rates of emergency department respiratory presentations at Port Pirie and regional comparators were calculated as age-standardised rates. The data show that increases in ambient SO 2 concentrations are associated with increased rates of emergency department respiratory presentations of Port Pirie residents, in which children are over-represented. The 30-day rolling average of respiratory presentations was significantly associated (p < 0.05) with incremental increases in SO 2. Analysis of the relationship between lead in air and blood lead shows that annual geometric mean air lead concentrations need to be <0.11 μg/m3 to ensure the geometric mean blood lead of Port Pirie children under 5 years is ≤5 μg/dL. For children aged 24 months, lead in air needs to be no greater than 0.082 μg/m3 (annual geometric mean) to ensure geometric mean blood lead does not exceed 5 μg/dL. Current smelting emissions continue to pose a clear risk of harm to Port Pirie children. Allowable emissions must be lowered significantly to limit adverse childhood health outcomes including respiratory illness and IQ, academic achievement and socio-behavioural problems that are associated with lead exposure at levels experienced by Port Pirie children. Current SO 2 levels are likely to be responsible for increased rates of emergency department respiratory presentations in Port Pirie compared with other South Australian locations. As a minimum, Australian SO 2 air quality standards need to be enforced in Port Pirie to better protect human health. Lead in air needs to be approximately 80% lower than the current national standard (0.5 μg/m3) to ensure that the geometric blood lead of children under 5 years is less than or equal to 5 μg/dL. Unlabelled Image • Lead and SO 2 smelter emissions continue to pollute Port Pirie, Australia. • 47% of children under 5 had a blood lead >5μg/dL in 2017. • Air lead needs to fall to less than 0.11µg/m3 to keep blood lead below 5µg/dL. • The 1-hr SO 2 air standard (0.2 ppm) has been exceeded >1000 times since 2003. • Emergency department respiratory presentations are associated with SO2 levels. [ABSTRACT FROM AUTHOR]

Data-driven modeling has been widely recognized as an effective and essential approach for predicting key quality variables in industrial processes. However, due to the long production process and the dynamic fluctuation of operating conditions, it is necessary to integrate data from various spatial and temporal points to comprehensively describe the production process. Furthermore, data is characterized by massive redundancies and high dimensionalities, which pose challenges for modeling dynamic processes. To address these issues, this paper proposes a strategy of spatio-temporal bidirectional redundancy removal to extract dynamic features and applies it to quality prediction. Firstly, it constructs input samples with the spatio-temporal two-dimensional structure. Then, information redundancy is removed by implementing feature extraction in both the spatial and temporal directions, respectively. Additionally, a spatio-temporal weight matrix is used in this process to capture dynamic information which is more related to the output quality variable. Its effectiveness was verified by applying it to the debutanizer column process and the leaching process in zinc smelting. Results show that the proposed strategy generates efficient dynamic features with no information redundancy and low dimensionalities. Moreover, it outperforms other common types of dynamic process modeling methods in terms of quality prediction performance. • A novel dynamic feature extraction strategy is proposed. • W-(2D) 2 PCA is proposed to extract dynamic features for the quality prediction. • The strategy generates features with no information redundancy and low dimensionalities. • The method outperforms other dynamic process modeling methods in the quality prediction. [ABSTRACT FROM AUTHOR]

Zinc smelting wastewater contains high concentrations of Cd. Here, the treatment efficiency of Cd using electrodialysis was evaluated. In addition, scale accumulation of ion-exchange membrane (IEM) was analyzed, and fouling control was studied. The results showed that spacers effectively improved the limiting current density but accelerated foulant accumulation. The Cd-treatment efficiency improved to 85.4% without a spacer. Dissolved organic carbon (DOC) and hydrophobic DOC levels in diluted water decreased by 0.65 mg L−1 and 2.1 mg L−1, respectively; in contrast, hydrophilic DOC level increased by 1.45 mg L−1. Some of the hydrophobic DOC in the diluted water was converted to hydrophilic DOC and subsequently to low-molecular-weight (LMW) DOC. DOC level in the concentrated water did not change substantially, but the LMW fraction of the hydrophilic DOC increased. In the cation-exchange membrane, a material composed of calcium sulfate accumulated in the bottom layer, and hydroxides of divalent and trivalent ions accumulated on top of it. In contrast, the anion-exchange membrane was fouled by humic substances. In terms of fouling control, physical and acid cleaning of IEMs was more effective than the reversal operation. [Display omitted] • Electrodialysis can effectively remove high concentrations of Cd. • Spacers promote heavy metal hydroxide formation, leading to fouling. • Natural organic matter affects fouling of anion-exchange membranes. • Hydrophobic dissolved organic carbon (DOC) in diluate decreased during treatment. • Hydrophilic DOC and its ratio to low molecular weight DOC increased. [ABSTRACT FROM AUTHOR]

Abstract We investigated potentially toxic metal (loid)s (arsenic, As; cadmium, Cd; chromium, Cr; copper, Cu; mercury, Hg; lead, Pb; selenium, Se; and zinc, Zn) in agricultural samples (i.e., Solanum tuberosum L. tubers (potatoes) and their planting media) in the indigenous zinc smelting area of northwestern Guizhou Province, China. Based on the pollution index values for As, Cd, Pb and Zn, the order of the samples was as follow: slag > planting soil with slag > planting soil without slag, and the order of the samples in terms of the bioconcentration factor was the opposite. Cr, Cu and Hg were present in the planting soil with and without slag at slight pollution levels, and the other potentially toxic metal (loid)s had different degrees of contamination. Additionally, the potentially toxic metal (loid) contents in potato were under their limit values except for Cd (all samples) and Pb and Se (some samples). All bioconcentration factors for potatoes were below 0.5, and no health risk index value for potatoes was higher than 0.1. Therefore, although no significant health risk associated with potentially toxic metal (loid)s via consuming potato exists for either adult men or women in the research area, the Cd concentration in this crop should be monitored. Highlights • The planting media order in terms of PI for As, Cd, Pb and Zn is slag > planting soil with slag > planting soil without slag. • The planting media order in terms of BCFs for As, Cd, Pb and Zn is opposite that of the PI order. • Solanum tuberosum L. is an excluder or is tolerant of As, Cd, Cr, Cu, Hg, Pb, Se and Zn. • There is no significant health risk associated with potato consumption for either adult men or women in the research area. • The As, Cd, Pb, Se and Zn contents in crops in the indigenous zinc smelting area should be monitored. [ABSTRACT FROM AUTHOR]

To determine the effects of dietary constituents on soil Pb oral bioavailability, Pb relative bioavailability (RBA) in 3 soils contaminated by zinc smelting (ZS), wire-rope production (WR), and metal mining (MM) was measured under fasted and fed states with 9 foods. Under fasted state, Pb-RBA was 84.4 ± 10.3, 82.6 ± 4.70, and 32.3 ± 1.10% for ZS, WR, and MM soils; however, it decreased by 1.3–3.5 fold to 23.9–58.8, 25.6–49.9, and 14.8–24.2% under fed states with foods excluding Pb-RBA with egg in WR soil (97.3 ± 4.46%), and with cabbage and egg in MM soil (40.0 ± 8.62 and 44.4 ± 0.96%). In the presence of foods, egg and pork with significantly higher protein and fat contents leaded to the highest soil Pb-RBA (44.4–97.3%), while Pb-RBA determined with mineral-rich mouse feed was 1.6–7.9 fold lower (9.41–13.5%), suggesting high fat and protein foods tended to increase soil Pb-RBA, while high mineral diets decreased soil Pb-RBA. The increased Pb-RBA of MM soil with cabbage compared to fasted state was due to high organic content in cabbage, which could increase soil Pb solubility by inhibiting Fe and Pb co-precipitation in the intestine. For accurate assessment of health risks of contaminated soils, dietary influence on soil Pb-RBA should be considered. [ABSTRACT FROM AUTHOR]

Abstract In order to understand the size distribution and the main kind of heavy metals in particulate matter on the lead and zinc smelting affected area, particulate matter (PM) and the source samples were collected in Zhuzhou, Hunan Province from December 2011 to January 2012 and the results were discussed and interpreted. Atmospheric particles were collected with different sizes by a cascade impactor. The concentrations of heavy metals in atmospheric particles of different sizes, collected from the air and from factories, were measured using an inductively coupled plasma mass spectrometry (ICP-MS). The results indicated that the average concentration of PM, chromium (Cr), arsenic (As), cadmium (Cd) and lead (Pb) in PM was 177.3 ± 33.2 μg/m3, 37.3 ± 8.8 ng/m3, 17.3 ± 8.1 ng/m3, 4.8 ± 3.1 ng/m3 and 141.6 ± 49.1 ng/m3, respectively. The size distribution of PM displayed a bimodal distribution; the maximum PM size distribution was at 1.1–2.1 μm, followed by 9–10 μm. The size distribution of As, Cd and Pb in PM was similar to the distribution of the PM mass, with peaks observed at the range of 1.1–2.1 μm and 9–10 μm ranges while for Cr, only a single-mode at 4.7–5.8 μm was observed. PM (64.7%), As (72.5%), Cd (72.2%) and Pb (75.8%) were associated with the fine mode below 2.1 μm, respectively, while Cr (46.6%) was associated with the coarse mode. The size distribution characteristics, enrichment factor, correlation coefficient values, source information and the analysis of source samples showed that As, Cd and Pb in PM were the typical heavy metal in lead and zinc smelting affected areas, which originated mainly from lead and zinc smelting sources. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of plant litter input on the chemical and microbiological characteristics of zinc smelting slag. A laboratory microcosm experiment was conducted to evaluate the effect of litters from four specific plant species ( Trifolium repens (TR), Rumex acetosa (RA), Buddleia davidii (BD), and Neyraudia reynaudiana (NR)) on slag quality after 90 days of litter decomposition. The nutrient and organic matter contents, enzyme activities, abundances of microbes, and availability of heavy metals were measured. The results showed that compared with the control treatment (CK), the four litter treatments significantly increased the concentrations of nutrients (N, P, K) and organic matter, enzyme activity (invertase, phosphatase, and urease), and the abundances of three dominant microbes (bacteria, fungi, and actinomycetes) in the substrate. RA and TR litters showed the highest improvement in the nutrient contents and microbiological characteristics of slag. The presence of plant litters strongly influenced the availability of heavy metals, and the effect varied among plant litter species and types of heavy metals. For example, both TR and RA litters significantly increased the content of available Cu and reduced those of Cd and Pb, while all four litters significantly reduced Zn availability. A comprehensive evaluation of the abovementioned factors showed that the application of RA litter had a greater effect on the improvement of the micro-ecological environment and nutrient contents of the slag. This result suggested that the selection of suitable pioneer plant litter as an organic amendment could significantly enhance the quality of zinc smelting slag using indigenous methods. [ABSTRACT FROM AUTHOR]

Soil contamination due to atmospheric deposition of metals originating from smelters is a global environmental problem. A common problem associated with this contamination is the discrimination between anthropic and natural contributions to soil metal concentrations: In this context, we investigated the characteristics of soil contamination in the surrounding area of a world class smelter. We attempted to combine several approaches in order to identify sources of metals in soils and to examine contamination characteristics, such as pollution level, range, and spatial distribution. Soil samples were collected at 100 sites during a field survey and total concentrations of As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, and Zn were analyzed. We conducted a multivariate statistical analysis, and also examined the spatial distribution by 1) identifying the horizontal variation of metals according to particular wind directions and distance from the smelter and 2) drawing a distribution map by means of a GIS tool. As, Cd, Cu, Hg, Pb, and Zn in the soil were found to originate from smelter emissions, and As also originated from other sources such as abandoned mines and waste landfill. Among anthropogenic metals, the horizontal distribution of Cd, Hg, Pb, and Zn according to the downwind direction and distance from the smelter showed a typical feature of atmospheric deposition (regression model: y  =  y 0 + αe − βx ). Lithogenic Fe was used as an indicator, and it revealed the continuous input and accumulation of these four elements in the surrounding soils. Our approach was effective in clearly identifying the sources of metals and analyzing their contamination characteristics. We believe this study will provide useful information to future studies on soil pollution by metals around smelters. [ABSTRACT FROM AUTHOR]

Co-contaminant behavior of arsenic (As) and selenium (Se) in groundwater is examined in this study at a former lead and zinc smelting facility. We collected water quality data, including concentrations of trace metals, major ions, and metalloid speciation, over a 15-year period to document long-term trends and relationships between As, Se, geochemical parameters, and other redox-sensitive trace metals. Concentrations of dissolved As and Se were negatively correlated (Kendall's Tau B correlation coefficient, r = −0.72) and showed a distinctive L-shaped relationship. High-concentration arsenic wells (>5 mg L −1 ) were characterized by intermediate oxidation-reduction conditions (75 < Eh < 275 mV), near-neutral pH (6.1–7.9), low Ca/Na ratios, elevated Fe and Mn concentrations, and high proportions of As(III) relative to total dissolved As. High-concentration Se wells (>500 μg L −1 ) were characterized by more positive Eh (305–500 mV), low Fe concentrations, and high proportions of As(V). Batch micocosm experiments showed that aquifer solids contain mineral surfaces and/or microbial communities capable of removing selenate from groundwater. Electron microprobe and Se K -edge X-ray absorption near-edge spectroscopic analyses demonstrated that Se was predominantly associated with elemental Se in the reduced aquifer solids. Factor analysis revealed three discernible groupings of trace metals. Group I includes U, Se, and nitrate-N, all of which are mobile under oxygenated to moderately oxygenated conditions. Group II includes elements that are mobile under Fe(III)-reducing conditions: Fe, total dissolved As, As(III), and ammonium-N. Group III elements (Mo, Sb, and V) showed mobility across the entire range of redox conditions encountered in site groundwater; As(V) clustered with this group of elements. Geochemical modeling suggests that As and Se species were in a state of disequilibrium with respect to measured parameters indicative of redox conditions, although predicted patterns of redox-controlled mobility and attenuation were confirmed. This analysis is important to better understand groundwater contaminant behavior in response to redox conditions ranging from oxic/suboxic to Fe(III)-reducing, but excluding sulfate-reducing conditions. [ABSTRACT FROM AUTHOR]

The contribution by anthropogenic sources to abnormally high Zn concentrations in soils with naturally abundant Zn was investigated at a contaminated site surrounding a Zn smelter in eastern Korea. Nineteen soil samples were collected within a 2 km radius of the smelter, and analyzed for metal concentrations and Pb isotope ratios using an inductively coupled plasma-optical emission spectrometer and -mass spectrometer, respectively. Higher Zn concentrations in locations closer to the smelter implied that the smelter was the source of the Zn pollution. Lead isotope ratios ( 206/207 Pb) from soil samples assumed to be unaffected by the smelter were higher than those found in the contaminated area, suggesting that the raw materials of Zn concentrates (ZnS, sphalerites) and smelting by-products from the smelter with low 206/207 Pb ratios were the anthropogenic Zn source impacting the area. To verify this finding, the mineralogical forms of Zn found in the different soil fractions were investigated by X-ray diffraction analysis, scanning-electron-microscope energy-dispersive spectrometer analysis, and sulfur element analysis. Since approximately 50% of Zn concentrates have particle sizes less than 0.044 mm, the observation of sphalerites and elevated sulfur concentrations in the finer soil fraction (< 0.044 mm) provide substantial support to the hypothesis that the deposition of airborne Zn-containing dust from the smelter is responsible for the high Zn concentration in the area. [ABSTRACT FROM AUTHOR]

• Human methylmercury (MeHg) exposure pathways were quantified by stable isotope in typical Hg-emission areas. • CSIA can track pollution sources of MeHg and inorganic Hg (IHg) in rice grain. • Fish MeHg potentially originates from plankton in the euphotic zone. • Fish IHg was partially derived from in vivo demethylation of MeHg. • Positive shifts of δ202Hg from diet to hair indicated internal MeHg demethylation. Anthropogenic mercury (Hg) emissions have increased significantly since the Industrial Revolution, resulting in severe health impacts to humans. The consumptions of fish and rice were primary human methylmercury (MeHg) exposure pathways in Asia. However, the lifecycle from anthropogenic Hg emissions to human MeHg exposure is not fully understood. In this study, a recently developed approach, termed MeHg Compound-Specific Isotope Analysis (CSIA), was employed to track lifecycle of Hg in four typical Hg-emission areas. Distinct Δ199Hg of MeHg and inorganic Hg (IHg) were observed among rice, fish and hair. The Δ199Hg of MeHg averaged at 0.07 ± 0.15 ‰, 0.80 ± 0.55 ‰ and 0.43 ± 0.29 ‰ in rice, fish and hair, respectively, while those of IHg averaged at − 0.08 ± 0.24 ‰, 0.85 ± 0.43 ‰ and − 0.28 ± 0.68 ‰. In paddy ecosystem, Δ199Hg of MeHg in rice showed slightly positive shifts (∼0.2 ‰) from those of IHg, and comparable Δ199Hg of IHg between rice grain and raw/processed materials (coal, Hg ore, gold ore and sphalerite) were observed. Simultaneously, it was proved that IHg in fish muscle was partially derived from in vivo demethylation of MeHg. By a binary model, we estimated the relative contributions of rice consumption to human MeHg exposure to be 84 ± 14 %, 58 ± 26 %, 52 ± 20 % and 34 ± 15 % on average in Hg mining area, gold mining area, zinc smelting area and coal-fired power plant area, respectively, and positive shifts of δ202Hg MeHg from fish/rice to human hair occurred during human metabolic processes. Therefore, the CSIA approach can be an effective tool for tracking Hg biogeochemical cycle and human exposure, from which new scientific knowledge can be generated to support Hg pollution control policies and to protect human health. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new leaching method of zinc and germanium was designed. • The occurrence state of Ge, Fe, Si and Zn before and after leaching was shown. • The leaching rate was increased by 10% and the reaction time was shortened by 50%. • Lead is highly enriched and recovered. As a byproduct of lead and zinc smelting, zinc oxide dust often contains abundant valuable metals such as zinc and germanium. To improve the leaching of zinc and germanium in sulfuric acid, the correlation between germanium and other elements in zinc oxide dust, the phase composition of the main elements, and Eh-pH dominant area of germanium were analyzed. Finally, ultrasonic waves and potassium dichromate were added to enhance the leaching of zinc and germanium in the leaching process. The results show that the best recoveries of zinc and germanium are 99.25 % and 90.44 %, respectively, under the optimum conditions. Compared with the existing process, the leaching rate is increased by 8 ∼ 10 % and the leaching time is reduced by more than 50 %. There are fewer impurities in the leaching residue after leaching, and the lead content is about 50 % and can be directly recycled back into the lead smelting process for recycling. In conclusion, the oxidation leaching of zinc and germanium from zinc oxide dust with potassium dichromate under ultrasound proves to be efficient, economical and practical. [ABSTRACT FROM AUTHOR]

Trace elements (TE) are indicative of industrial pollution in soils, but geochemical methods are difficult to implement in contaminated sites with large numbers of samples. Therefore, measurement of soil magnetic susceptibility (MS) has been used to map TE pollutions, albeit with contrasted results in some cases. Effective radium concentration ( EC Ra ), product of radium concentration by the emanation factor, can be measured in a cost-effective manner in the laboratory, and could then provide a useful addition. We evaluate this possibility using 186 topsoils sampled over about 783 km 2 around two former lead and zinc smelters in Northern France. The EC Ra values, obtained from 319 measurements, range from 0.70 ± 0.06 to 12.53 ± 0.49 Bq·kg − 1 , and are remarkably organized spatially, away from the smelters, in domains corresponding to geographical units. Lead-contaminated soils, with lead concentrations above 100 mg·kg − 1 < 3 km from the smelters, are characterized on average by larger peak EC Ra values and larger dispersion. At large scales, away from the smelters, spatial variations of EC Ra correlate well with spatial variations of MS, thus suggesting that, at distance larger than 5 km, variability of MS contains a significant natural component. Larger EC Ra values are correlated with larger fine fraction and, possibly, mercury concentration. While MS is enhanced in the vicinity of the smelters and is associated with the presence of soft ferrimagnetic minerals such as magnetite, it does not correlate systematically with metal concentrations. When multiple industrial and urban sources are present, EC Ra mapping, thus, can help in identifying at least part of the natural spatial variability of MS. More generally, this study shows that EC Ra mapping provides an independent and reliable assessment of the background spatial structure which underlies the structure of a given contamination. Furthermore, EC Ra may provide a novel index to identify soils potentially able to fix leached components. [ABSTRACT FROM AUTHOR]

The study of zinc distillation technology in ancient China has recently been published by Zhou et al. 2012, 2014. From these two papers we know more detail informations about it. But, there are still some key technologies we do not know exactly. The first question is if there is any difference between the coal used as fuel or as reductant agent? We also don't know the exact smelting temperature in this kind of smelting activity. The last and most important thing, we know that the retorts were charged with zinc ores, coal and charcoal, but we know little about the exact ration between them. In order to solve these questions, this paper presents the analytical study by OM, XRF, XRD, DIL and SEM-EDS of zinc production that remains from the archaeological site of Lijiangerdui, in the same region, dated to the Ming dynasty, probably a few years earlier than the previous studies. The results indicated that there are different coals used for the smelting activity, and the smelting temperature can be as high as 1306 °C, all of these are over 1180 °C. The ratios for the raw material may be 1:2.7 [(coal + charcoal) / zinc ores]. [ABSTRACT FROM AUTHOR]

Since lager quantities of the zinc (Zn) smelting slags were traditionally dumped at the indigenous Zn smelting sites, the release characterization of potentially toxic elements (PTEs) from the Zn smelting slags under various environmental conditions were of great significance for an environmental risk analysis. The acidification of the Zn smelting slags to pH= 4 and 6 would result in the leaching concentrations of Cd and Mn exceeding the fourth–class standard of surface water quality standard in China (GB3838–2002). Notably, most metals exhibited an amphoteric leaching pattern, where the highest leached concentrations of As, Cd, Cu, Mn, Pb, and Zn were 4.15, 4.21, 140.0, 78.1, 156.9 and 477.0 mg/L, respectively. In addition, the highest release of toxic metals within 96 h reached 0.17 % of As, 3.50 % of Cd, 2.77 % of Cu, 6.92 % of Mn, 0.13 % of Pb, and 2.57 % of Zn, respectively. The combined results of various characterization techniques suggested that the PTEs remobilization effected by rhizosphere–like organic acids were mainly controlled by the precipitation of newly formed Fe, Mn and Al (hydr) oxides and the complexation of organic ligands. The present study results could provide valuable insights into the long–term leaching behaviors of PTEs from the Zn smelting slags to reduce ecological hazard. [Display omitted] • The leaching behaviors of toxic elements were investigated at the slag dumping sites. • The leaching concentrations of toxic elements varied depending on pH and particle sizes. • The second order model described the metal release under the rhizosphere environment. • Fe (oxyhydr) oxides controlled the metal remobilization by rhizosphere–like organic acids. [ABSTRACT FROM AUTHOR]

In this study, ground surface dust samples from two contrasting areas, a former zinc smelting area in Guizhou Province and a common urban district in Wuhan city, Hubei Province, China, were assessed for in vitro Pb bioaccessibility using a physiologically based extraction test (PBET). Extremely elevated concentrations of Pb (220–6348 mg/kg) and other trace metals were observed in the zinc smelting area. While moderate high metal concentrations (79–1544 mg/kg of Pb) in the urban dusts were attributed to various urban activities, coal combustion and traffic emissions. Lead bioaccessibility in the stomach-phase varied from 17.6 to 76.1% and no significant difference was found between industrial and urban dust samples. Compared with the stomach-phase, Pb bioaccessibility in the more alkaline intestinal-phase was considerably lower (1.2–21.8%). A significantly negative correlation was found between dust Ca concentrations and Pb bioaccessibility in the intestinal-phase, suggesting that Ca plays an important role in reducing the bioaccessible Pb in the intestinal-phase. The estimated Pb exposure based on gastric bioaccessible Pb was 13.9 and 1.8 μg/kg day for children living in the industrial and urban areas, respectively, accounting for 85% and 41% of their corresponding total Pb exposure. [ABSTRACT FROM AUTHOR]

The production of zinc has played an important role in both the technological and the economic history of ancient china. However, the lack of studies on zinc smelting remains with convincing chronology limits our understanding on the history of zinc production. Our recent field survey in Yunnan province, southwest china, has discovered zinc-smelting sites in Qiaojia County. The location is in the Jinsha River Valley, which has abundant lead, zinc, copper and mineral coals. Large numbers of crucible and slags were excavated, which indicates a large scale of zinc production in the region. A profile of 10 layers containing slag pellets altered with fluvial sediments presents clear evidence of a series of zinc smelting events. The ages of both the fluvial sediment and slag layers have been obtained using luminescence dating. Detailed chronology indicates that large scale of zinc production in this area can be traced back to late Qing Dynasty (AD 1854). [ABSTRACT FROM AUTHOR]

A comprehensive comparison of the levels and profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in fly ash samples from multiple industrial sources may help to prioritize sources and to understand discrepancies in profiles. In this study, PCDD/F data from 113 fly ash samples from 14 sources reported in previous studies were summarized and compared. The highest PCDD/F levels occurred in samples from secondary copper smelting (SCu). Although PCDD/F levels from secondary zinc smelting (SZn) were slightly lower than those of SCu, the PCDD/F profiles varied widely between the two sources. For SCu, more chlorinated homologs were dominant, with highest degrees of chlorination being 6.6 for PCDF and 7.2 for PCDD. For SZn, less chlorinated homologs were dominant, with lowest degrees of chlorination being 4.4 for PCDF and 4.8 for PCDD. We speculate that copper and zinc might promote PCDD/F formation by catalyzing different pathways of thermal reactions. Diagnostic ratios of specific PCDD/F congeners for different sources were suggested to identify potential sources of PCDD/Fs in the environment. Equations describing correlations between congeners and PCDD/F toxic equivalents were established, which may be useful for rapid and inexpensive screening of the toxic levels of PCDD/Fs in fly ash samples. [ABSTRACT FROM AUTHOR]

Contaminated sites pose a significant risk to human health and the regional environment. A comprehensive study was dedicated to improving the understanding of the contamination condition of a smelting site by integrating multi-source information through 3D visualization techniques. The results showed that 3D visualization reveals excellent potential for application in the environmental studies to finely depict contamination in soils and establish relationships with geological features, hydrological conditions, and sources of contamination. The contamination plume model revealed that the soil environment at the site was seriously threatened by toxic metals, and dominated by multi-metal contamination, with contamination soil volume ranked as Cd > As > Pb> Zn > Hg. The stratigraphic model revealed the heterogeneous geological conditions of the site and identified the mixed fill layer as the primary remediation soil layer. The permeability model revealed that soil permeability significantly influenced contamination dispersion and contributed to delineate the contamination boundary accurately. The ecological hazard model targeted the high ecological hazard area and determined the high hazard contribution of Cd and Hg in the site soil. The outcomes can be directly applied to actual site remediation and provide a reference for the contaminated sites evaluation and restoration in the future. [Display omitted] • Multi-source model establishes relationships between influences on site pollution. • 3D visualization holds great potential for finely delineating soil pollution. • 3D visualization of multi-metal composite pollution plumes was realized. [ABSTRACT FROM AUTHOR]

• There was severe Cd and Cr pollution in the soil of Hutou Village. • The primary source of soil pollution was the use of coal. • Mineralogical and geochemical characteristics revealed the migration direction of the pollution. • The contents of REY and Eu in the soil were significantly higher than those in road dust. • The fractionation of LREY and HREY in the soil was more substantial than that in the road dust. This study aimed to reveal the status and source apportionment of trace element soil pollution in a village with a relatively high incidence of lung cancer in China and determine the element migration characteristics from coal to road dust and soil. To this end, 24 soil samples, 48 road dust samples (from a previous study), and 2 coal samples were collected; major element oxides, V, Cr, Co, Ni, Cu, Zn, Zr, Cd, and rare earth elements were analyzed; minerals were identified by SEM-EDX and XRD; a geoaccumulation index (I geo), Spearman's correlation analysis, provenance index (PI) and positive matrix factorization (PMF) were carried out to assess the status and source apportionment of soil pollution; and mineralogical and geochemical methods were used for provenance discrimination and migration characteristics identification. The results demonstrated that (1) the Cd and Cr pollution of the soil was severe and originated mainly from indigenous zinc smelting, agricultural activities, and the use of coal. (2) The pollution migrated from Yantang coal to the road dust to the soil through mineralogical and geochemical methods. (3) A stronger fractionation of light and heavy rare earth elements was observed in the soil than in the road dust, indicating a single pollution source in the road dust and a complex source in the soil. (4) The primary reason for the lower rare earth element values in the road dust could be physical separation by the wind. [ABSTRACT FROM AUTHOR]

[Display omitted] • Building "ionic liquid (IL) + tributyl phosphatev(TBP) + Di(2-ethylhexyl)phosphoric acid (P204)" extraction system. • TBP and [BMIm]PF 6 (IL) together inhibit the P-OH activity of P204, which makes the extraction performance of Fe3+ was completely suppressed. "IL + TBP + P204" extraction system has an exclusive extraction of indium ions from H 2 SO 4 solution and avoid iron ions cyclic accumulation in organic phase. And indium can be efficiently stripped from "IL + TBP + P204" organic phase by HCl. For low indium ion concentration, high Fe/Zn ions concentration of acid leaching solution of wet zinc smelting waste slag, it was challenging to efficiently separate indium because iron ion was usually extracted simultaneously with indium ion by sulfonated kerosene and acid-phosphate-type extractants. It was found that the extraction system of"hydrophobic ionic liquid and acid-phosphate-type extractants and tributyl phosphate (TBP)"(i.e. "IL + P204 + TBP") could extract indium ion exclusively and indium ion could be stripped efficiently with HCl. Research results indicated that the best extraction conditions by "IL + TBP + P204" were sulfur acid solution pH = 0.9 ∼ 1.1, IL:TBP:P204 = 2:3:1, A/O = 3:1, t = 5 ∼ 10 min. The indium extraction rate was 98.11% and Fe 0.0% under the optimal extraction conditions. The best indium stripping conditions of "IL + TBP + P204" system were HCl 1.5 ∼ 2 mol/L, O/A = 1:1, t = 15 min. The indium stripping efficiency was 100% under the optimal stripping conditions. Mechanism investigations showed that indium ions in sulfuric acid solution were extracted into the organic phase as InSO 4 +, and also showed that TBP and [BMIm]PF 6 (IL) together inhibited the P-OH activity of P204, which made the extraction performance of Fe3+ was completely suppressed. Thus, "IL + TBP + P204" extraction system had an exclusive extraction of indium ions from sulfuric acid solution and avoided iron ions cyclic accumulation in organic phase. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel two-stage process is proposed to recovery of Zn and Pb from waste zinc smelting slag. [•] Brick with low bulk density and high compressive strength is made by zinc smelting slag and clay. [•] The leaching toxicity of sintered brick is below the regulatory thresholds of Chinese National Standards. [ABSTRACT FROM AUTHOR]

Highlights: [•] Slag heap after Zn–Pb smelting was disturbed during removal. [•] The interior comprises fine grained material dominated by secondary phases. [•] Interior of the slag heap can be more intensely weathered than the outside parts. [•] The weathering is probably facilitated by long-term disposal. [•] The weathered material can pose environmental risk due to high metal contents. [ABSTRACT FROM AUTHOR]

Toxic metal(loid) (TM) soil pollution at large-scale non-ferrous metal smelting contaminated sites is of great concern in China, but there are no detailed reports relating to them. A comprehensive study was conducted to determine contamination characteristics and horizontal and vertical spatial distribution patterns of soils at an abandoned zinc smelting site in Southern China. The spatial distribution of TMs revealed that soil environmental quality was seriously threatened, with Cd, Zn, As, Pb and Hg being the main contaminants present. The distribution of all TMs showed strong spatial heterogeneity and were expressed as a "patchy aggregation" pattern due to strong anthropogenic and production activities. Vertical migration of TMs indicated that the pollutants were mainly concentrated in the fill layers. Different contaminants had various migration depths, with migration occurring as: Cd > Hg > As > Zn > Pb> Cu> Mn> Sb. Analysis of their spatial variability showed that As, Pb, Cd and Hg had strong regional spatial variability. This research provides a new approach to comprehensively analyze TM pollution characteristics of non-ferrous smelting sites. It provides valuable information for guiding post-remediation strategies at abandoned non-ferrous metal smelting sites. [Display omitted] • Multidimensional distribution pattern of TMs at smelting sites is described. • Variability of TM pollution is determined both horizontally and vertically. • TM distribution revealed "patchy aggregation" due to production activities. • TMs revealed varying migration depths, expressed as: Cd > Hg > As > Zn > Pb> Cu > Mn > Sb. [ABSTRACT FROM AUTHOR]

Smelting slags is a well-known industrial solid waste, while there were limited studies on the key factors controlling the potential health risks caused by these smelting slags. In this work, the metal bioaccessibility in the size fractionated–zinc smelting slags was examined using various In vitro assays, in combination with multidisciplinary methods. The results indicated that the bioaccessible fractions of heavy metals showed a significant difference, but no statistical difference among different particle sizes of the zinc smelting slags. The bioaccessible metal fractions in the gastric (GP) and gastrointestinal (GIP) phases were 0 (Cr) – 91.39% (Cd)) and 0 (Cr) – 47.80% (Ni). Among the studied metals, Cd, Cu, Mn, Pb and Zn were the most bioaccessible to human. The Pearson correlation analysis showed that the carbonate bound phases of heavy metals were responsible for their bioaccessibility in GP and GIP. Moreover, the combined results of multidisciplinary characterization also further implied that the solubility behaviors of toxic elements in the smelting slags were dominated by soluble metal bearing– mineral phases and absorbable Fe, Mn and Al–rich minerals and metal bearing–precipitates during SBRC extractions. Therefore, these study results provide a insight into the potential controls of metal bioaccessibility in the zinc smelting slags, which was of great significance from the aspects of their resource recycling and risk management. [Display omitted] • The zinc smelting slags were studied with multidisciplinary characterization. • Cd, Cu, Mn, Pb and Zn were the most bioavailable elements in the smelting slags. • Bioaccessibility was not affected by particle sizes based on the statistical results • The bioaccessible elements originated from the dissolution of carbonate minerals. • Slag mineralogy played important roles in the metal bioaccessibility assessment. [ABSTRACT FROM AUTHOR]

The lack of emission data of major Cd-emitting enterprises has long limited the source apportionment of soil cadmium (Cd). Non-ferrous metal enterprises (NMEs) contribute the most Cd emissions in China in recent years. We estimated the cumulative Cd emission of 8750 NMEs across China through public data collection and material balance methods for the first time. The results showed that the total Cd emissions were estimated at 133,177 tons, of which 78.68% contributed by zinc primary smelting and mining. The emission hotspots are mainly concentrated in the south of the Yangtze River, such as Nanling Mountain areas, Nanpan River Basin, and Jincheng River Basin, as well as a few parts of the North and Northwest China. Then a significant positive spatial correlation was furtherly detected between NMEs and soil Cd, except for secondary smelting enterprises. Moreover, the hotspots of soil Cd pollution caused by NMEs were identified across China. By promoting the accounting calibrator from annual emission intensity of regional (mainly provincial) scale to the cumulative emission of site-specific enterprise in its entire life cycle, this study realized the finer description of the spatial heterogeneity of Cd emission from non-ferrous industry on a large scale and make it possible to refine the reliability of follow-up site-specific source apportionment, by introducing the emission intensity instead of the enterprise sites density. Finally, a modified approach for the regional source apportionment of soil pollution was proposed to obtain a more realistic and precise drawing. The results pointed out key NMEs subcategories and the affected hotspots which require continuous strengthening of Cd-related rectification. This methodological framework is expected to contribute to the precise management and differential sources control of Cd pollution and can be further extended to other pollutants for the precise targeting of key industries and hotspots during source pollution control in the future. [Display omitted] • The cumulative Cd emissions of national non-ferrous metal enterprises were estimated. • Varied Cd emission was observed between different non-ferrous industrial subcategories. • An improved approach framework included Cd emission intensity for source identifying was proposed. • Pollution hotspots of soil Cd and associated key industrial subcategories were first identified across China. [ABSTRACT FROM AUTHOR]

[Display omitted] • A cheap and readily available adsorbent using intermediate as raw material was purposefully synthesized. • The as-prepared ZnS-300℃-120 min adsorbent exhibits the best performance for Hg0 capture performance. • Abundant unsaturated sulfur species are generated on the surface of ZnS adsorbent. Exploiting a cheap and readily available adsorbent for elemental mercury (Hg0) immobilization from zinc smelting flue gas has become an urgent requirement to ensure the sustainable development of zinc smelting industry. Herein, a novel protocol of using intermediate products derived from zinc smelting process to synthesize porous ZnS adsorbent is proposed in this study to provide a practicable support for efficient capture of Hg0. The as-prepared ZnS-300℃-120 min adsorbent exhibits an outstanding performance for Hg0 capture. Approximately 100% of Hg0 can be entrapped even under the extreme conditions of high gaseous hourly space velocity (GHSV) values and wide temperature ranges. Additionally, its saturated adsorption capacity and average adsorption rate reach 3.6 mg/g and 1.3 μg/g/min, respectively, much higher than common adsorbents. The in-situ Raman spectra and XPS spectra results confirm that the unsaturated short-chain S n 2- is dominant adsorption site. The active S n 2- site would be formed on the surface of ZnS during the calcination process. The formed S n 2- ligand would promptly and selectively react with Hg0 to form stable HgS, consequently achieving the efficient immobilization of Hg0. After Hg0 capture, the spent ZnS adsorbent can be safely disposal of by thermal desorption, simultaneously realizing the recycling of zinc and mercury resource. The purposefully synthesized ZnS adsorbent can provide a practical and yet easy-to-adopt strategy for mercury pollution control of zinc smelting industry, while opening a new path to recycle valuable metal from smelting waste. [ABSTRACT FROM AUTHOR]

Abstract: Historic emissions from two zinc smelters have injured the forest on Blue Mountain near Palmerton, Pennsylvania, USA. Seedlings of soybeans and five tree species were grown in a greenhouse in a series of mixtures of smelter-contaminated and reference soils and then phytotoxic thresholds were calculated. As little as 10% Palmerton soil mixed with reference soil killed or greatly stunted seedlings of most species. Zinc was the principal cause of the phytotoxicity to the tree seedlings, although Mn and Cd may also have been phytotoxic in the most contaminated soil mixtures. Calcium deficiency seemed to play a role in the observed phytotoxicity. Exposed soybeans showed symptoms of Mn toxicity. A test of the effect of liming on remediation of the Zn and Mn phytotoxicity caused a striking decrease in Sr-nitrate extractable metals in soils and demonstrated that liming was critical to remediation and restoration. [Copyright &y& Elsevier]

Abstract: In this study, field measurements were conducted to estimate and characterize the atmospheric emission levels and profiles of polychlorinated biphenyls (PCBs) from multiple industrial thermal processes. The emission levels and profiles of PCBs from five types of thermal processes at twenty-three plants were studied and compared with eight processes reported in our previous studies. Correlation analysis was preformed to identify a marker congener for emission of ΣPCB. A significant correlation was observed between congener CB-118 and ΣPCB (R 2 =0.65 and p <0.01), which suggests that CB-118 is a good marker congener for emission of ΣPCB. The profiles of PCBs emitted from the thirteen thermal processes were compared, and this information could be used for studying source–receptor relationships and identifying the specific sources of PCBs. To prioritize the sources for control, the concentrations of PCBs from thirteen industrial thermal sources were compared. The PCB concentrations from secondary zinc smelting and thermal wire reclamation were about one to three order magnitude higher than those of other sources, which suggests that these two sources be given priority in PCB source control. Finally, the atmospheric emission factors of PCBs from the thirteen industrial sources were summarized, and these data will be useful for developing an integrated emission inventory of PCBs. [Copyright &y& Elsevier]

Abstract: The Flin Flon copper–zinc smelter is a site of concern as it has been the largest single source of atmospheric mercury emissions in Canada. Variations in total mercury concentration and mercury isotopic composition were determined in three lake sediment cores at different distances from the Flin Flon smelter. Total mercury concentrations ranged from 90 to 19,000ng/g and were much higher in cores obtained closer to the smelter. The observed mass dependent mercury isotope fraction (MDF) varied significantly among sediment cores collected closer to the smelter (−0.67 to −1.48‰) and cores collected from further away (−1.44 to −2.71‰). Mass independent fraction (MIF) was detectable in some but not all samples (−0.05 to 0.14‰). A simple binary mixing model showed that mercury in all sediment samples investigated in this study originated in variable proportions from the Flin Flon smelter. The study demonstrated that mercury isotope ratio measurements could serve as an effective tool for tracing mercury contamination caused by atmospheric emissions from metal smelting activities. [Copyright &y& Elsevier]