Zinc Smelting Plant Research Articles

Fixing sulfur dioxide by feeding calcine oxide into the rotary volatilization kiln in zinc smelting plant.

Sulfur dioxide (SO2) is a toxic pollutant and its fixation is a high cost but imperative task for sulfide metallurgy industry. Although being a mature technology for on-line fixation of SO2 by limestone injection in coal-fired boilers, its application is rarely investigated in the sulfide metallurgy plant. Extending this technology to the metallurgy industry is highly plausible, but with the feasibility and practicability waiting to be uncovered. Herein, feeding CaO into the rotary volatilization kiln as SO2-fixation agent is demonstrated to be an efficient in-furnace desulfurization strategy for zinc smelting plant. The sulfur distribution within the entire smelting process is systematically analyzed, determining that the critical procedure for pressuring the desulfurization system is the rotary volatilization kiln. The thermodynamics analysis shows that addition of CaO is feasible for SO2 fixation by forming CaS or restraining the reductive decomposition of SO42-. The industrial tests, including the online monitoring of kiln flue gas and kiln slag analysis, validate the thermodynamics analysis, realizing a 24.6% reduction of SO2 in the flue gas by converting gaseous SO2 to solid CaS via feeding 20% CaO. The present study highlights an effective strategy for on-line fixing the SO2, being a potential way for relieving the desulfurization pressures in zinc sulfide metallurgy plant.

Distribution Characteristics of Heavy Metals in Soils Affected by Different Land Use Types in a Superimposed Pollution Area with High Geological Background

The high geological background and the residual pollution of historical zinc smelting in the karst area of northwest Guizhou has led to serious soil heavy metal pollution. In order to understand the characteristics of soil heavy metal pollution in agricultural land, wasteland, and forestland, 126 surface and profile soil samples were collected from a typical zinc powder factory-polluted small watershed in Weining County, Northwest Guizhou Province. The concentrations and distribution characteristics of Cd, As, Pb, Cu, and Zn in soils were studied. The results showed that the average ω(Cd), ω(As), ω(Pb), ω(Cu), and ω(Zn) in the surface soil were 8.14, 45.07, 263.97, 41.36, and 716.98 mg·kg-1, respectively, which were 1.29-12.33 times higher than the background values. The content of heavy metals in soil of different land uses in descending order was agricultural land, wasteland, and forestland. From the perspective of spatial distribution, the soil with high heavy metal concentration was concentrated around the zinc smelting plant and slag, and the accumulation of heavy metals in soil was greatly affected by the pollution sources of mining activities but less affected by the land use mode. In soil profile, heavy metals in the surface layer were generally higher than those in bottom layers, showing a significant difference (P<0.05) in wasteland. Five heavy metals in 80-100 cm soil were higher than the background value, reflecting the existence of a high geological background value. Correlation analysis and principal component analysis showed that Pb, Zn, and As in the surface soil were mainly affected by human activities such as mining and transportation, whereas Cd and Cu were both affected by high geological background and human activities. The single ecological risk coefficient of Cd in soil was the highest, which reached very strong or very strong risk, whereas As, Zn, Cu, and Pb reached slight or medium risk. The comprehensive potential ecological risk index indicated strong ecological risk, which in agricultural land was higher than that in wasteland and forestland. In the karst high geological background area, the influence of lead and zinc smelting on the distribution and accumulation of heavy metals in soils was greater than that of land use; soil heavy metal pollution was serious, and ecological risk was high in this area. Therefore, strict control of heavy metal-contaminated soil should be strengthened.

Superposition Effects of Zinc Smelting Atmospheric Deposition on Soil Heavy Metal Pollution Under Geochemical Anomaly

Guizhou Province is covered by a large area of carbonate rocks where, with a higher background of heavy metals under the geochemical anomaly, more than 3.6 × 105 ha of heavy metal–contaminated soil in the northwest area is related to historical indigenous zinc smelting. To explore the superposition effect of industrial source atmospheric deposition on soil, two watersheds were selected for study: 1) Maoshui reservoir watershed (MS), where there is a zinc smelting plant, and 2) Haishe lake watershed (HS), which was the control. We collected atmospheric depositions and soil for 3 years and analyzed Cadmium (Cd), lead (Pb), chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn) content. The results show that the heavy metals in the atmospheric deposition of the pollution watershed in MS were much higher than those in the control site, HS. The deposition fluxes of Cd, Pb, Cr, Ni, and Zn in MS were 27.8, 602, 145, 43.9, and 2,225 mg·m−2·a−1, respectively, and were 1.37–2.01 times higher than in HS. Soil heavy metals in MS were 1.01–5.69 times higher than in HS. The elevated concentrations were found focused from northeast to southwest around the plant but was distributed uniformly in HS. The average concentration of Cd, Pb, and Zn in the soil was 6.54, 67.4, and 264 mg·kg−1, respectively, in HS, which represents a high geochemical background even without pollution. After 13 years of deposition by prediction, the contribution of the atmospheric deposition on the soil in the zinc-smelting area was lowest, at 5.10%, for Ni, and highest, at 17.9%, for Cd. Principal component analysis of atmospheric deposition and soil heavy metals reflected that the pollution sources in MS were more diversification than those in HS. Zinc smelting atmospheric deposition showed superposition effects on the accumulation of heavy metals in soil under the geochemical anomaly in this region.

Health risk assessment of heavy metals in street dust around a zinc smelting plant in China based on bioavailability and bioaccessibility.

In order to investigate pollution level, chemical speciation and health risk of exposure to heavy metals in street dust from smelting district, we carried the following studies: (a). the differences in the morphology of street dust in smelting and non-smelting districts using a scanning electron microscope; (b). the chemical speciation and bioavailability of heavy metals in <100μm and <63μm particles near a smelting district using a modified three-stage BCR sequential extraction procedure and in vitro digestion test, respectively; (c). the evaluation of the non-carcinogenic risk of children and adults exposure to dust based on bioaccessibility. The results showed that most of the dust particles near Huludao Zinc Plant (HZP) were relatively solid with less porosity, which might originate from incompletely burned mineral particles from the smelting process. The concentrations of Pb, Cd and Cu were much higher than the background levels: 1560, 178.5 and 917.9mgkg-1 in <100μm dust samples, and 2099, 198.4, 1038mgkg-1 in <63μm dust samples, respectively. Pb was mostly present in the reducible fraction and the acid exchangeable fraction, while Cd and Cu were the most common heavy metals in the acid exchangeable fraction and oxidizable fraction, respectively. The rank order of bioaccessibility for the gastric and intestinal phase was Cd (58.13%)>Pb (50.00%)>Cu (19.19%) and Cd (20.36%)>Cu (15.67%)>Pb (5.08%), respectively. Hand-to-mouth ingestion poses the greatest non-carcinogenic exposure risk compared with other exposure pathways. When bioavailability is taken into account, children experienced higher non-carcinogenic and carcinogenic risks of dust exposure compared with adults, and the <63μm particles posed greater risks than <100μm particles.

Simultaneous Removal of Nickel and Cadmium During the Cold Purification of Zinc Sulfate Solution

One of the most important steps in the zinc processing industries is the removal of impurities. In this step, cobalt, nickel and cadmium are removed from the leach solution by hot and cold purification, respectively. In this research, the effective parameters on cold purification reactor of Dandi zinc smelting plant (Zanjan—Iran) such as temperature, consumption of zinc dust, residence time, copper sulfate additive, pH of solution, zinc dust particle size and mixing speed are studied. Results demonstrated that optimum concentration of zinc dust to remove impurities properly is 2 g/L, which is less than the factory’s consumption by up to 30%. It was also found that the copper sulfate had no effect on the removal process of nickel and cadmium, and hence exclusion of this additive can cause cost-effectiveness in the process. Optimum amounts of residence time, temperature, pH and mixing speed are 75 min, 80 °C, 4.5 and 400 rpm, respectively. It was demonstrated that the smaller particle size has more effect on the removal of nickel and cadmium. The maximum efficiency was observed at < 45 µm. More ever, the high density of zinc ions had a deterrent effect on the efficiency of nickel and cadmium removal.

Lead Recovery from Zinc Leaching Residue by Flotation

With the depletion of natural mineral resources, secondary resources such as zinc leaching residue (ZLR) should be processed to recover valuable metals. In this study, flotation recovery of lead (anglesite) in ZLR from a zinc smelting plant was investigated, and the mechanism studied by using Fourier-transform infrared (FTIR) spectroscopy measurements. The flotation results indicated lead recovery and grade of the concentrates of 76.39% and 47.18%, respectively, after flotation of one-roughing, one-scavenging, three-cleaning, and middles back to the flowsheet in turn after washing ZLR with tap water. FTIR measurements suggested that salicylhydroxamic acid was chemically adsorbed onto the surface of anglesite (PbSO4). The results of this study show that lead in ZLR can be successfully recovered by flotation, having not only economic but also environmental benefits.

Industrial Symbiosis: A Case Study Involving a Steelmaking, a Cement Manufacturing, and a Zinc Smelting Plant

Industrial Symbiosis is the part of Industrial Ecology that manages environmental and economic improvements through the exchange of materials, resources, utilities, and by-products between members of a network of companies, such as supply chains or technological clusters. The purpose of this article is to analyze the mutual exchange of materials that occur among a steelmaking plant, vendors, and other business partners in a network of industrial companies. The research object is a steelmaking plant of Brazil. Almost 100 % of the raw material of the steelmaking industry is metallic scrap originated from other industries. Likewise, the steelmaking industry routes almost 100 % of the waste to other companies provided there is commercial and logistical feasibility. Seven major companies form the network, but this study involves only three companies. The complete study involves the entire network. This study involves a steelmaking plant, that generates by-products (slag, electric arc furnace dust, mill scale, and zinc sludge) used by a cement plant and a zinc smelting plant as raw materials. The zinc smelting plant closes the loop of the circular economy, as the sludge serves as raw material for zinc ingots used by the steelmaking plant in the galvanization process of its wire rod manufacture. The study concluded that synergetic relationships of mutual interest are the main factor that drives the industrial symbiosis in the network. Environmental aspects are also relevant. Even existing mutual interest, industrial symbiosis strongly depends on external factors, like logistics and legal compliance. The companies must rely on intermediate transportation companies that usually have difficulties to comply with the legislation and rarely has competitive costs or high production scale.

Distribution and health risk assessment of heavy metals in soil surrounding a lead and zinc smelting plant in Zanjan, Iran

ABSTRACTOne of the problematic issues in soil pollution studies is heavy metal particles which are produced by mines and smelting units and spread through wind action and/or runoff. Pollution and health risk assessment of cadmium, lead, zinc, copper, and nickel in soil around the lead and zinc smelting factory was carried out in Zanjan City, Iran. Contamination factor (Cf), pollution load index (PLI), geoaccumulation index (Igeo), hazard quotient (HQ), hazard index (HI), and carcinogenic risk were pollution and human health risk assessment metrics in this study. Based on the Iranian soil guideline value, soil samples in the studied areas were contaminated the least by copper and nickel and the most by cadmium. PLI results showed that soils near the production line were heavily or extremely heavily polluted. The results of Cf and Igeo showed that lead and zinc were the most important contaminants. Health risk assessment indicated that lead and cadmium in soil were the main contaminants, which pose both carcinogenic and non-carcinogenic risks to human health; carcinogenic risk levels were unacceptably high (above 1 × 10−4). It can be concluded that mining and smelting activities degrade soil quality in this region and the soil pollution might be extended to farming areas.

Lead Contamination and Source Characterization in Soils Around a Lead–Zinc Smelting Plant in a Near-Urban Environment in Baoji, China

Economic reforms in China since 1978 have promoted nationwide socioeconomic advancement but led to a considerable amount of environmental pollution. The distribution and sources of Pb in a typical peri-urban industrial part of Baoji, China, were assessed by determining the Pb contents and isotopic compositions in 52 topsoil samples from the study area. The topsoil samples were polluted averagely with 40.88mg Pb kg-1, was 1.86 times higher than the Pb content of local background soil (22.04mg kg-1). Pb isotopic compositions were determined by analyzing samples prepared using total digestion and acid extraction methods. Radiogenic isotopes contributed more to the Pb concentrations in the acid extracts than in the total digests. This was shown by the 207/206Pb and 208/206Pb ratios, which were 0.845-0.88 and 2.088-2.128, respectively, in the acid extracts and 0.841-0.875 and 2.086-2.125, respectively, in the total digests. This indicates that anthropogenic sources of Pb could be identified more sensitively in acid extracts than in total digests. The Pb isotope ratios showed that burning coal and smelting ore are the predominant anthropogenic sources of Pb in the study area, i.e., a lead-zinc smelter and a coking plant are major sources of Pb in the study area.

Environmental mobility of trace elements present in dusts emitted from Zn–Pb metallurgical processes

The paper presents results of investigations into possibility of migration to the soil and water environment of trace elements present in one of the main phases, zinc sulphide, emitted in dusts from various operations of pyrometallurgical extraction of Zn and Pb at the Miasteczko Śląskie Zinc Smelting Plant. The quantity of elements was estimated on the basis of: (1) dust fall, (2) zinc sulphide content in dust, (3) element content in zinc sulphide and (4) mobility of zinc sulphide under the hypergenic conditions of the soil and water environment of the Smelting Plant area. Among the elements considered, arsenic emitted with zinc sulphide contained in dusts from the Sintering Machine will pose a potential hazard for the soil and water environment of the Miasteczko Śląskie Zinc Smelting Plant area.

&lt;p&gt;&lt;strong&gt;Oribatid mite communities in contaminated soils nearby a lead and zinc smelting plant in Zanjan, Iran&lt;/strong&gt;&lt;/p&gt;

Many studies have shown that the composition of invertebrate communities in soil changes under the influence of stressors in the soil ecosystem. Conversely, an observed altered community structure may be indicative of stress. In this study we aimed to investigate responses of oribatid mite communities to heavy metal (zinc, copper and cadmium) contamination of grasslands nearby a lead and zinc smelting plant at Zanjan, Iran. Soil analysis showed that the Zanjan plant is a major source of zinc and cadmium in the area. No relationship could be found between metal pollution and total density of oribatids, but the number of species and the Shannon diversity index were lowest in the sites polluted by zinc and cadmium. Species diversity was significantly negatively correlated with zinc and cadmium, but not with copper concentrations. Oribatula (Zygoribatula) connexa connexa Berlese, 1904, was a dominant species at all sites; the percentage dominance of this species was highest at the most polluted site. Our survey confirms that oribatid mite communities display a great variety of responses to heavy metals, depending on the species.

Characterization and environmental risk assessment of heavy metals in construction and demolition wastes from five sources (chemical, metallurgical and light industries, and residential and recycled aggregates).

Total concentrations of heavy metals (Cu, Zn, Pb, Cr, Cd, and Ni) were measured among 63 samples of construction and demolition (C&D) wastes collected from chemical, metallurgical and light industries, and residential and recycled aggregates within China for risk assessment. The heavy metal contamination was primarily concentrated in the chemical and metallurgical industries, especially in the electroplating factory and zinc smelting plant. High concentrations of Cd were found in light industry samples, while the residential and recycled aggregate samples were severely polluted by Zn. Six most polluted samples were selected for deep research. Mineralogical analysis by X-ray fluorescence (XRF) spectrometry and X-ray diffraction (XRD), combined with element speciation through European Community Bureau of Reference (BCR) sequential extraction, revealed that a relatively slight corrosion happened in the four samples from electroplating plants but high transfer ability for large quantities of Zn and Cu. Lead arsenate existed in the acid extractable fraction in CI7-8 and potassium chromium oxide existed in the mobility fraction. High concentration of Cr could be in amorphous forms existing in CI9. The high content of sodium in the two samples from zinc smelter plants suggested severe deposition and erosion on the workshop floor. Large quantities of Cu existed as copper halide and most of the Zn appeared to be zinc, zinc oxide, barium zinc oxide, and zincite. From the results of the risk assessment code (RAC), the samples from the electroplating factory posed a very high risk of Zn, Cu, and Cr, a high risk of Ni, a middle risk of Pb, and a low risk of Cd. The samples from the zinc smelting plant presented a high risk of Zn, a middle risk of Cu, and a low risk of Pb, Cr, Cd, and Ni.

Content, speciation and pollution assessment of Cu, Pb and Zn in soil around the lead–zinc smelting plant of Baoji, NW China

The concentration and speciation of Cu, Pb and Zn in soil samples collected around the lead–zinc smelting plant of Baoji, NW China, were determined using X-ray fluorescence spectrometry and the modified European Community Bureau of Reference sequential extraction procedure. The single pollution index (PI) and the integrated pollution index (IPI) were calculated to evaluate the contamination levels of Cu, Pb and Zn in the soil. The mean concentrations of Cu, Pb and Zn in the topsoil samples are 31.8, 41.3 and 102.6 mg kg−1, respectively, higher than their concentrations in the control sample. The concentrations of Cu, Pb and Zn decreased significantly with depth from 0 to 35 cm, while they were relatively constant for depths between 35 and 100 cm. The concentrations of Cu, Pb and Zn in topsoil north of the lead–zinc smelting plant decreased exponentially with distance from the plant. Cu and Zn in the soil are mainly associated with the residual fraction, while Pb is dominated by the reducible and residual forms. The mobile fractions of Cu, Pb and Zn in topsoil are Pb (60.1 %) > Cu (20.1 %) ≈ Zn (20.6 %). The PI for Cu, Pb and Zn varies from 1.1 to 1.4, 1.0 to 2.5 and 1.1 to 2.0, with means of 1.2, 1.4 and 1.4, respectively, indicating that Cu, Pb and Zn are all moderately polluted in the topsoil around the lead–zinc smelting plant. IPI values range from 1.1 to 2.0 with an average of 1.3, showing that the topsoil samples are moderately contaminated by Cu, Pb and Zn.

Residents health risk of Pb, Cd and Cu exposure to street dust based on different particle sizes around zinc smelting plant, Northeast of China.

The residents health risk of Pb, Cd and Cu exposure to street dust with different particle sizes (<100 and <63 μm) near Huludao Zinc Plant (HZP) was investigated in this study. The average concentrations of Pb, Cd and Cu in the <100-μm and <63-μm dust were 1,559, 178.5, 917.9 and 2,099, 198.4, 1,038 mg kg(-1), respectively. It showed that smaller particles tended to contain higher element concentrations. Metals in dust around HZP decreased gradually from the zinc smelter to west and east directions. There was significantly positive correlation among Pb, Cd and Cu in street dust with different particle sizes. The contents of Pb, Cd and Cu in dust increased with decreasing pH or increasing organic matter. Non-carcinogenic health risk assessment showed that the health index (HI) for children and adult exposed to <63-μm particles were higher than exposed to <100-μm particles, which indicated that smaller particles tend to have higher non-carcinogenic health risk. Non-carcinogenic risk of Pb was the highest in both particle sizes, followed by Cd and Cu. HI for Pb and Cd in both particle sizes for children had exceeded the acceptable value, indicated that children living around HZP were experiencing the non-carcinogenic health risk from Pb and Cd exposure to street dust.

Leachability of cadmium, lead, and zinc in a long-term spontaneously revegetated slag heap: implications for phytostabilization

Purpose: For abandoned slag heaps, the spontaneous establishment of a vegetation cover is usually considered beneficial as it represents a means of phytostabilization. However, for slag containing heavy metals, such a vegetation cover has a potential long-term effect on the fate of the metals. The objective of this study was to investigate how the long-term spontaneous revegetation of a slag heap can affect the fractionation and the leachability of Cd, Zn, and Pb. Materials and methods: Soils from two plots covered by either Armeria maritima or Agrostis tenuis and a bare plot soil were sampled from a slag heap from a zinc smelting plant and characterized. The BCR sequential extraction scheme was adopted to determine the metal pools. The leachability of Cd, Pb and Zn was assessed by means of a leaching column experiment. Results and discussion: Long-term presence of a plant cover increased the proportion of Zn in the most mobile fraction and Pb in the fraction bound to organic matter. Cd distribution was relatively unaffected. Overall, the metal leachability was enhanced in the revegetated soils, notably due to higher organic anion release. However, responses of metal behavior to revegetation depended on the established plant species. The highest leachability of Cd was found in the soil covered by A. tenuis while the highest leachability of both Zn and Pb was observed in the soil below A. maritima. Conclusions: Any remediation strategy for metal-rich waste dumps by phytostabilization should take into careful consideration the potential long-term mobilization effect of plant establishment on heavy metals. We conclude that when using pioneer plants for phytostabilization purposes, preference should be given to pseudo-metallophyte over hyperaccumulator species.

Determination of historical emission of heavy metals into the atmosphere: Celje case study

The research shows that in the Celje area (Slovenia), the historical anthropogenical emissions are 1,712 tons of Zn and 9.1 tons of Cd. For Zn, this value represents approximately 0.3% of the total Zn production in that area. Close to the former zinc smelting plant, the “Zn precipitation” has been estimated to be up to 0.036 mm. The 100-year Zn production left behind a heavily contaminated area with maximum concentrations of Zn of up to 5.6% in attic dust and 0.85% in the soil, and 456 mg/kg of Cd in attic dust and 59.1 mg/kg in the soil. The calculation of historical emissions is based on the data of heavy metals concentration in the attic dust at 98 sampling points and on the data from 19 measurement sites of the weight of total monthly air deposit. The main idea behind determining past emissions is that when the weight of the deposited dust on a small area is multiplied by the concentration of the element in that area, the mass of the polluter which has been transported to the place of interest by air can be calculated. If we sum up all the weight over the whole geochemical anomaly, we get the quantity of historical emissions.

Modelling of atmospheric dispersion of heavy metals in the Celje area, Slovenia

The aim of this research was to determine how fast the level of heavy metal concentrations in the air decreases in relation to increasing distance from the source of pollution and what the influence area is of the zinc smelting plant which existed for 100 years in Celje. In that period it produced approximately 580,000 tons of raw Zn from sphalerite ore by the pyrometallurgical process. The production left behind a heavily contaminated area, where the concentrations of Pb and Zn in the soil can be expressed as a percentage. A model has been made on the basis of the data of concentrations of Zn and Cd in the soil and attic dust regarding the distance and direction from the source of the pollution. Because Celje lies in a basin we chose a linear model, which describes the decreasing of the concentrations of Zn and Cd only in one direction. Sampling has been conducted on the four river valleys which stretch from the source of the pollution in all four directions: north, west, south and east, up to 13 km from the source. The power function with a negative exponent was used. With the solution to the calculated functions according to the distance, we can estimate the theoretical distance when the concentrations drop to the natural background level. The range of influence of the zinc smelting plant has been estimated to be between 14 and 52 km for the presence of anthropogenic Zn in attic dust and between 9 and 14 km for the presence of anthropogenic Zn in the soil, depending on the direction from the plant. Correlations between the measured values and the ones from the model are high: from 0.75 up to 0.98.

Health risk of Hg, Pb, Cd, Zn, and Cu to the inhabitants around Huludao Zinc Plant in China via consumption of vegetables

Huludao Zinc Plant in Huludao City, China is the largest zinc smelting plant in Asia. Heavy metals have contaminated its neighboring environment seriously. We collected 20 vegetables and the corresponding soil samples from eight sampling plots near Huludao Zinc Plant to investigate health risk of Hg, Pb, Cd, Zn, and Cu to the inhabitants around Huludao Zinc Plant in China via consumption of vegetables. Transfer factor (TF) values of Hg, Pb, Cd, Zn, and Cu from soil to vegetable and the target hazard quotients (THQs) to the possible health risks to local population through the food chain transfer were calculated accordingly. TF values of heavy metals from soil to vegetable decrease in the order of Cd>Zn>Cu>Pb>Hg. These TF values of leaves are higher than other tissues. Daily intakes of Hg, Pb, Cd, Zn, and Cu through the consumption of vegetables are 1.322, 574.3, 301.4, 5263, and 292.5 microg, respectively, for adults, and 1.029, 446.8, 234.5, 4095, and 227.6 microg, respectively, for children around Huludao Zinc Plant. This would lead to potential health risk, especially for children, since Cd or Pb individual THQ is high than 1. The total metal THQs (TTHQs) due to consumption of vegetables for adult and child are 5.79-9.90, 7.6-13.0, respectively. Comparing TTHQs in the sampling plots of different distances to Huludao Zinc Plant, it indicate that the health risks to inhabitants close to Huludao Zinc Plant (<500 m) is the highest, and at >1000 m distance is relatively higher than in 500-1000 m distance. However, the inhabitants who lived in 500-1000 m distance to Huludao Zinc Plant is also experiencing the adverse health risk due to TTHQ being higher than 1.

Mercury contamination and health risk to crops around the zinc smelting plant in Huludao City, northeastern China

The Huludao zinc plant in Liaoning province, northeast China was the largest in Asia, and its smelting activities had seriously contaminated soil, water and atmosphere in the surrounding area. For the first time, we investigated the total mercury (THg) content in maize, soybean, broomcorn, 22 vegetables, and the soil around their roots from eight sampling plots near the Huludao zinc plant. THg contents of the seeds of maize, soybean, and broomcorn are 0.008, 0.006, and 0.057 mg kg(-1), respectively, with the broomcorn being the highest, exceeding the maximum level of contaminant in food (GB2762-2005) by 4.7 times. The edible parts of vegetables are also contaminated with a range of mercury contents of 0.001-0.147 mg kg(-1) (dry weight). THg contents in plant tissue decrease in the order of leaves > root > stalk > grain. Using correlation analysis, we show that mercury in the roots of these plants is mainly derived from soil, and the uptake of gaseous mercury is the predominant path by which the mercury accumulated in the foliage. The average and maximum mercury daily intake (DI) of adult around the Huludao zinc plant via consuming vegetables are 0.015 and 0.051 microg/kg/d, respectively, and those of children are 0.02 and 0.07 microg/kg/d, respectively. The average and maximum weekly intakes of total mercury for adult are 2.1 and 7.1%, respectively, of the provisional tolerable weekly intake (PTWI), and 2.8 and 9.7%, respectively, of the PTWI for children.

Mobility of heavy metals in self-burning waste heaps of the zinc smelting plant in Belovo (Kemerovo Region, Russia)

Approximately 70,000 tons of slags, containing a high concentration of fine-grained carbon and heavy metals were accumulated in the town of Belovo (Kemerovo region, Russia) as a result of Zn-smelting between 1950 and 1994. Spontaneous ignition of fine-grained carbonaceous material and the subsequent burning of the waste heaps produced a zoning pattern which is characterized by three types of altered waste material: burned (or pyrometamorphic) waste, metamorphosed waste, and weakly altered waste. The self-combustion process is the reason for a redistribution of various elements. Leaching tests were carried out to understand the behavior of soluble (extracted by distilled water) and mobile (extracted by 1N HCl) metal forms; water analyses were performed using atomic absorption spectroscopy. The mobile metal species were accumulated close to the combustion center, in the burned and metamorphosed waste. In contrast to this, the soluble species were precipitated further away from the combustion center, on the surface of the waste heaps near active fumaroles, which provide evidence for ongoing combustion in the interior parts of the heaps. These observations are confirmed by mineralogical studies using routine mineralogical techniques: elementary copper and newly formed zincite and willemite are found in the burned and thermally metamorphosed waste, whereas soluble sulfates of Cu, Zn and Fe were deposited in the weakly altered zones near the surface of the waste heaps. The relative ability of the studied elements to migrate, determined as the proportion of the mobile or soluble to total metal concentrations, decreases in the order Cd>Zn>Cu>Pb>Fe for both the soluble and mobile forms. Primary metal-bearing waste material appears to be more resistant to weathering than the secondary phases formed as a result of combustion. Every hour, drainage waters remove about 3 kg Zn and 2 kg Cu from the waste heaps.