Slag Sites Research Articles

Migration mechanism of PTEs in polymetallic mines under pioneer phytoremediation: A Lanmuchang mercury-thallium mine perspective

The establishment of pioneer plants in waste slag sites not only modifies the nutrient content of the waste, but also plays a significant role in regulating the pH and potentially toxic elements (PTEs), thereby providing favorable conditions for the quick introduction of other plants. However, the mechanisms by which pioneer plants impact the migration and transformation of PTEs in polymetallic mines have rarely been studied. In this study, we investigated the effects of pioneer phytoremediation on the migration and transformation of PTEs, specifically thallium (Tl), mercury (Hg), arsenic (As), and antimony (Sb), in mercury-thallium mine waste. The results showed that pioneer phytoremediation increased esters and ethers containing C-O and P-O groups in dissolved organic matter, which subsequently formed soluble complexes with Hg, As, and Sb. Nevertheless, pioneer phytoremediation reduced the migration of Tl in the waste, this was mainly because pioneer phytoremediation reduced Fe3+ in silicate minerals and iron-containing minerals to more reactive Fe2+, thereby increasing the electronegativity (El) of the waste and enhancing its adsorption capacity for metal cations, such as Hg and Tl, thus maintaining electrical neutrality. However, the increased El of the waste was detrimental to the adsorption of negatively charged oxygen-containing anions, such as As and Sb. At the same time, the dissolution of Fe2+ resulted in the release and mobility of As and Sb that had been adsorbed onto iron oxides. The results offer significant theoretical support for guiding the ecological restoration of PTEs in polymetallic mines.

Chemodiversity of dissolved organic matter and its association with the bacterial community at a zinc smelting slag site after 10 years of direct revegetation

Dissolved organic matter (DOM) plays a critical role in driving the development of biogeochemical functions in revegetated metal smelting slag sites, laying a fundamental basis for their sustainable rehabilitation. However, the DOM composition at the molecular level and its interaction with the microbial community in such sites undergoing long-term direct revegetation remain poorly understood. This study investigated the chemodiversity of DOM and its association with the bacterial community in the rhizosphere and non-rhizosphere slags of four plant species (Arundo donax, Broussonetia papyrifera, Cryptomeria fortunei, and Robinia pseudoacacia) planted at a zinc smelting slag site for 10 years. The results indicated that the relative abundance of lipids decreased from 18 % to 5 %, while the relative abundance of tannins and lignins/CRAM-like substances increased from 4 % to 10 % and from 44 % to 64 % in the revegetated slags, respectively. The chemical stability of the organic matter in the rhizosphere slag increased due to the retention of recalcitrant DOM components, such as lignins, aromatics, and tannins. As the diversity and relative abundance of the bacterial community increased, particularly within the Proteobacteria, there was better utilization of recalcitrant components (e.g., lignins/CRAM-like compounds), but this utilization was not invariable. In addition, potential preference associations between specific bacterial OTUs and DOM molecules were observed, possibly stimulated by heavy metal bioavailability. Network analysis revealed complex connectivity and strong interactions between the bacterial community and DOM molecules. These specific interactions between DOM molecules and the bacterial community enable adaptation to the harsh conditions of the slag environment. Overall, these findings provide novel insights into the transformation of DOM chemodiversity at the molecular level at a zinc smelting slag sites undergoing long-term revegetation. This knowledge could serve as a crucial foundation for developing direct revegetation strategies for the sustainable rehabilitation of metal smelting slag sites.

Vertical migration behavior simulation and prediction of Pb and Cd in co-contaminated soil around Pb-Zn smelting slag site

Heavy metal migration in soil poses a serious threat to the soil and groundwater. Understanding the migration pattern of heavy metals (HMs) under different factors could provide a more reasonable position for pollution evaluation and targetoriented treatment of soil heavy metal. In this study, the migration behavior of Pb and Cd in co-contaminated soil under different pH and ionic strength (NaCl concentration) was simulated using convective dispersion equation (CDE). We predicted the migration trends of Pb and Cd in soils after 5, 10, and 20 years via PHREEQC. The results showed that the migration time of Cd in the soil column experiment was about 60 days faster than that of Pb, and the migration trend was much steeper. The CDE was proved to describe the migration behavior of Pb and Cd (R2 > 0.75) in soil. The predicted results showed that Cd migrated to 15–20 cm of soil within 7 years and Pb stayed mainly in the top 0–6 cm of soil within 5 years as the duration of irrigation increased. Overall, our study is expected to provide new insight into the migration of heavy metal in soil ecosystems and guidance for reducing risk of heavy metal in the environment.

Organic amendment application affects the release behaviour, bioavailability, and speciation of heavy metals in zinc smelting slag: Insight into dissolved organic matter

Organic amendments are commonly used in assisted phytostabilization of mine wastes by improving their physicochemical and biological properties. These amendments are susceptible to leaching and degradation, resulting in the generation of dissolved organic matter (DOM), which significantly influences the geochemical behaviour of heavy metals (HMs). However, the geochemical behaviour of HMs in metal smelting slag driven by organic amendment-derived DOM remains unclear. In this study, we investigated the impact of cow manure-derived DOM on the release behaviour, bioavailability, and speciation of HMs (Cu, Pb, Zn, and Cd) in zinc smelting slag using a multidisciplinary approach. The results showed that DOM enhanced the weathering of the slag, with a minimal impact on the slag’s mineral phases, except for causing gypsum dissolution. The DOM addition resulted in a slight increase in HM release from the slag during the initial inoculation period, followed by a reduction in HM release during the later period. Furthermore, the DOM addition increased the diversity and relative abundance of the bacterial community. This, in turn, led to a decrease in the dissolved organic carbon (DOC) content and enhanced the transformation of labile DOM compounds into recalcitrant compounds. The variation in HM release during various inoculation periods can be attributed to the bacterial decomposition and transformation of DOM, which further enhanced the transformation of HM fractions. Specifically, during the later period, DOM promoted the conversion of a portion of the reducible and oxidizable fractions of Cu, Pb, and Zn into the acid-soluble and residual fractions. Moreover, it partially transformed the reducible, oxidizable, and residual fractions of Cd into the acid-soluble fraction. Overall, this study provides new insights into the geochemical behaviour of HMs in slag governed by the coupling effect of DOM and the bacterial community. These findings have implications for the use of organic amendments in assisted phytostabilization of metal smelting slag. Environmental implicationMetal smelting slag is hazardous due to its high levels of HMs, and its improper disposal has serious consequences for the ecosystem. Organic amendments are employed in assisted phytostabilization of the slag site by improving its microecological properties. However, the impact of organic amendment-derived DOM on HM migration and transformation in slag remains unclear. This study indicated that the coupling effects of DOM and microbes governed the geochemical behaviour of HMs in slag. These findings provide new insights into how organic amendments impact the geochemical behaviour of HMs in slag, contributing to the development of phytostabilization technology.

Quantitative Analysis of Soil Cd Content Based on the Fusion of Vis-NIR and XRF Spectral Data in the Impacted Area of a Metallurgical Slag Site in Gejiu, Yunnan

Vis-NIR and XRF spectroscopy are widely used in monitoring heavy metals in soil due to their advantages of being fast, non-destructive, cost-effective, and non-polluting. However, when used individually, XRF and vis-NIR may not meet the accuracy requirements for Cd determination. In this study, we focused on the impact area of a non-ferrous metal smelting slag site in Gejiu City, Yunnan Province, fused the pre-selected vis-NIR and XRF spectra using the Pearson correlation coefficient (PCC), and identified the characteristic spectra using the competitive adaptive reweighted sampling (CARS) method. Based on this, a quantitative model for soil Cd concentration was established using partial least squares regression (PLSR). The results showed that among the four fusion spectral quantitative models constructed, the model combining vis-NIR spectral second-order derivative transformation and XRF spectral first-order derivative transformation (D2(vis-NIR) + D1(XRF)) had the highest coefficient of determination (R2 = 0.9505) and the smallest root mean square error (RMSE = 0.1174). Compared to the estimation models built using vis-NIR and XRF spectra alone, the average computational time of the fusion models was reduced by 68.19% and 63.92%, respectively. This study provides important technical means for real-time and large-scale on-site rapid estimation of Cd content using multi-source spectral fusion.

Analyzing topsoil heavy metal pollution sources and ecological risks around antimony mine waste sites by a joint methodology

Studies on soil contamination caused by waste sites near antimony mining areas are scarce. For environmental protection, it is critical to investigate the contamination levels, spatial distribution, and ecological risk assessment of heavy metals (HMs) in the surface soils of different land use types around waste sites and to identify related potential sources. In this study, the pollution status, spatial distribution, sources and ecological risks of Hg, Pb, Cd, Cr, As and Sb in the surface soils of built-up areas, woodlands and croplands around the waste sites of antimony mining areas were resolved for the first time by combining self-organizing maps (SOM), K-means clustering, geographic information systems (GIS) and positive matrix factorization (PMF). According to the analysis results of soil samples, the average abundance order of HMs is: Sb > As > Cd > Pb > Cr > Hg. The cumulative geological index defines Sb as a severe pollution level. The pollution index shows that Sb and Cd in all samples are above the severe pollution level. The pollution load index shows that 67.7% of soil samples are heavily polluted. SOM and K-means divided the studied elements into three clusters and were combined with GIS analysis to from Cd as cluster 1, Sb and As as cluster 2, and Pb, Hg and Cr as cluster 3. The PMF analysis yielded three potential sources of heavy metals: natural sources dominated by Hg, Pb and Cr (48.6%), direct sources caused by the accumulation of waste sites represented by Sb and As (32.9%) and mixed sources caused by human activities and transportation represented by Cd (18.5%). Ecological risk shows that the risk of construction area is prominent, and Sb is the main contribution element of high risk. This study combines multiple methods to investigate the current status of heavy metal pollution in the soil environment around antimony mine slag sites, providing a theoretical basis for better research on the pollution of heavy metals in the soil around antimony mine slag sites and source control, and contributing to the scarcity of antimony mine slag site pollution research.

Effect of simulated root exudates on the distribution, bioavailability, and fractionation of potentially toxic elements (PTEs) in various particle size fractions of zinc smelting slag: Implication of direct revegetation

Direct revegetation is a promising strategy for phytostabilization of metal smelting slag sites. Slag comes into direct contact with root exudates when slag sites undergo direct revegetation. The slag particle size fractions are considered the key factor influencing the geochemical behaviour of potentially toxic elements (PTEs). However, the effects of root exudates on the geochemical behaviours of PTEs in various slag particle size fractions remain unclear. Here, the effects of simulated root exudates of perennial ryegrass (Lolium perenne) directly revegetated at a zinc smelting slag site on the distribution, bioavailability, and fractionation of PTEs (Cu, Pb, Zn, and Cd) in various slag particle size fractions were investigated. The results showed that PTEs mainly occurred in the <1 mm slag particles; the mass loads of PTEs in the <1 mm slag particles were higher than those in the >1 mm slag particles. The bioavailability of Cu, Zn, and Cd rather than Pb in the slag increased as the particle size decreased. There was a decrease in the <0.25 and 1–2 mm slag particles and an increase in the 0.25–0.5, 0.5–1, and >2 mm slag particles in the presence of root exudates. Root exudates enhanced the transformation of acid-soluble PTEs into other more stable fractions in various slag particle size fractions. Root exudates enhanced the aggregation of slag particles associated with the migration of PTEs, causing differences in the geochemical behaviour of PTEs in various slag particle size fractions. These findings are beneficial for understanding the geochemical behaviour of PTEs in metal smelting slags undergoing direct revegetation and provide an important basis for the guidance of environmental risk management of the revegetated metal smelting slag sites.

Influence mechanism of plant litter mediated reduction of iron and sulfur on migration of potentially toxic elements from mercury-thallium mine waste

The decomposition of plant litter in soil changes soil nutrient content and plays an important role in regulating soil pH and availability of potentially toxic elements (PTEs). However, there remains limited studies on the mechanism under which litter influences the transport of PTEs in the process of ecological restoration. This study examined the effect of plant litter decomposition mediated reduction of iron and sulfur components on migration of PTEs from mercury-thallium mine waste. The results showed that the four kinds of litter alleviated the acidity of the waste, especially the Bpa and Tre litter. The nitro and nitroso groups produced by the decomposition of the litter were adsorbed onto the waste, thereby providing an electron transfer medium for iron reducing microorganisms, such as Geobacter. This promoted the reduction and release of Fe3+ to Fe2+ and reduced the electronegativity (El) value of waste. The reduced El promoted the adsorption of metal cations such as Hg and Tl to maintain electrical neutrality. However, it was not conducive to the adsorption of oxygen containing anions of As and Sb. An increase in litter resulted in an increase in reductivity of mercury-thallium mine waste. This maintained the reduction of Fe3+ to Fe2+ and changed or destroyed the structure of silicate minerals. PTEs, such as Tl, Hg, As, and Sb, were released, resulting in reductions in their residual fraction. However, the strong reduction conditions, especially the decomposition of Bpa, caused part of the released Hg(II) combining with S2− produced by the reduction of SO42− to form insoluble HgS, thereby reducing its migration. The findings could provide a theoretical basis to guide the situ-control and ecological restoration of PTEs in waste slag site.

Vertical distribution of nutrients, enzyme activities, microbial properties, and heavy metals in zinc smelting slag site revegetated with two herb species: Implications for direct revegetation

Direct revegetation is an important measure to immobilize heavy metals and improve the microecological properties of metal smelting slag sites. However, the vertical distribution of nutrients, microecological properties, and heavy metals at a directly revegetated metal smelting slag site remains unclear. Here, the distribution characteristics of nutrients, enzyme activities, microbial properties, and heavy metals in the vertical profile at a zinc smelting slag site directly revegetated with two herb species (Lolium perenne and Trifolium repens) for 5 years were investigated. The results showed that the nutrient contents, enzyme activities, and microbial properties decreased with increasing slag depth after revegetation with the two herb species. The nutrient contents, enzyme activities, and microbial properties of the surface slag revegetated with Trifolium repens were better than those in the surface slag revegetated with Lolium perenne. The higher root activity in the surface slag (0–30 cm) resulted in relatively higher contents of pseudo-total and available heavy metals in the surface slag. Moreover, the contents of pseudo-total heavy metals (except for Zn) and available heavy metals in the slag revegetated with Trifolium repens were lower than those in the slag revegetated with Lolium perenne at most slag depths. Overall, the greater phytoremediation efficiency of the two herb species occurred mainly in the surface slag (0–30 cm), and the phytoremediation efficiency of Trifolium repens was higher than that of Lolium perenne. The findings are beneficial for understanding the phytoremediation efficiency of direct revegetation strategies for metal smelting slag sites.

The community assembly for understanding the viral-assisted response of bacterial community to Cr-contamination in soils

Microbial community assembly contributes to the restoration and rehabilitation of the disturbed ecosystems. However, the viral assembly mechanism and its difference from bacterial communities under soil contamination have not been previously reported. Here, clean, light and heavy chromium (Cr)-contaminated soils were collected from two Cr slag sites and adjacent soils in northwestern and southwestern China. Through metagenome and virome sequencing analysis, we found that the alpha diversity of bacterial genes (including overall genes and Cr detoxifying genes) showed no clear variance (p>0.05) across soils, indicating the functional redundancy in the bacterial communities. The assembly of both the bacteria and virus taxa were primarily controlled by deterministic process across soils The assembly of bacterial genes turned from stochastic processes to deterministic processes when the Cr content increased in soils. By contrast, the assembly of viral genes altered from deterministic processes in clean soil into stochastic processes in Cr-contaminated soils. Virus-host linkage results showed that the niche breadth of bacteria and viruses was closely related. The normalized stochasticity ratio of viral functional assembly was positively correlated with the Simpson index of the bacteria (p<0.05). The results suggested that the stochasticity of viral functional assembly was conducive to facilitating the functional redundancy of bacterial communities and their evolution toward the deterministic direction. • Bacteria maintained functional redundancy under Cr exposure. • Deterministic process dominated the assemblies of bacterial and viral taxa. • Bacterial and viral genes were driven by distinct processes due to Cr exposure. • Viral communities facilitated the functional redundancy of host bacteria.

Characteristics and source analysis of potentially toxic elements pollution in atmospheric fallout around non-ferrous metal smelting slag sites-taking southwest China as an example.

More accurate source analysis of potentially toxic elements (PTEs) in atmospheric fallout that endanger biodiversity and human health remains needed. This study determined the concentrations of seven PTEs, including Pb, Cd, As, Cu, Zn, Ni, and Cr, by inductively coupled plasma mass spectrometry (ICP-MS), and the sources of PTE pollution were quantified using multivariate statistical analysis, including principal component analysis (PCA), cluster analysis (CA), and Pearson correlation analysis, and Moran index was applied for mutual verification and supplementation. PCA and CA revealed that the same mixed sources of Pb, Cd, As, Cu, and Zn were found in the atmospheric dust fall in the study area, while Ni and Cr had the same source of pollution. Pearson correlation analysis provided that there were strong correlations between Pb-Cd, Pb-As, Pb-Cu, Cd-As, Cd-Cu, As-Cu, and Ni-Cr, indicating commonality between the two sources of heavy metal pollution. Additionally, the Moran index showed that strong spatial correlations were observed between Pb, Cd, As, Cu, and Zn, whose sources were mainly related to non-ferrous metal processing smelter smelting slag sites and an environmental company in the study area. However, no spatial correlation was found between Ni and Cr, which mainly originated from the local geological background.

Removal of arsenic in the leachate by a porous carbonaceous solid waste generated from pyrolysis of oily sludge

The leachate derived from lead smelting slag site is a potential hazard to the soil and water nearby due to its excessively high arsenic content. A porous carbonaceous solid waste (PCSW), resulting from the pyrolysis of oily sludge of tank bottom, was proposed to remove arsenic (As) from leachate. According to the results of As removal from simulated solution, PCSW can remove As efficiently and synchronously increase solution pH at equilibrium. The removal efficiency of As was 96.26% and the solution pH at equilibrium was 8.98 under the optimal conditions of PCSW dosage of 3 g⋅L−1, and initial As concentration of 12 mg⋅L−1 with the initial pH of 7.5. The adsorption rate of As was 0.319 g·(mg·min)−1, and the maximum adsorption capacity of As on PCSW was 45.314 mg⋅g−1. The removal of As from the solution was attributed mainly to the formation of stable calcium-arsenate precipitations and Fe–As complexes on PCSW surface. PCSW can also simultaneously and effectively remove the heavy metals (As, Pb, Zn, Cu, Cd) in leachate from lead smelting slag sites, and the residual concentration of all heavy metals were lower than the emission concentration (GB25466-2010, China). It is proved to be feasible for PCSW application in the treatment of leachate containing heavy metals.

Effect of different direct revegetation strategies on the mobility of heavy metals in artificial zinc smelting waste slag: Implications for phytoremediation

The establishment of vegetation cover is an important strategy to reduce wind and water erosion at metal smelting waste slag sites. However, the mobility of heavy metals in waste slag-vegetation-leachate systems after the application of revegetation strategies is still unclear. Large microcosm experiments were conducted for revegetation of waste slag for 98 d using combined amendments, i.e., phosphate rock and an organic waste coming from the anaerobic digestion of pig manure (named as biogas residue), and by single- and co-planted perennial ryegrass (Lolium perenne L.) and Trifolium repens (T. repens). The results showed that the application of biogas residue slightly increased the concentrations of Zn and Cd in the leachates; however, the establishment of plants could avoid the excessive leaching of heavy metals coming from the biogas residue. The bioavailability of Cu, Zn, and Cd slightly increased, but Pb bioavailability significantly decreased regardless of single- or co-planting patterns. Additionally, the bioavailability of Cu, Zn, and Cd in the waste slag revegetated with perennial ryegrass was lower than that in T. repens under the single-planting pattern. The change in the heavy metals bioavailability under different revegetation strategies was mainly due to the root-induced change in the pH and speciation of heavy metals in the waste slag. The application of biogas residue and phosphate rock tends to the immobilization of Pb. Heavy metals mainly accumulated in the underground parts of the two herbs, and the heavy metal contents in the underground parts of perennial ryegrass were higher than those in T. repens regardless of single- or co-planting patterns. The heavy metals accumulated in T. repens were lower than those in perennial ryegrass in the single-planting pattern. The bioaccumulation and transportation factors of the two herbs were extremely low. Thus, the two herbs are potential candidates for phytostabilization of zinc smelting waste slag sites.

Effects of four woody plant species revegetation on habitat improvement and the spatial distribution of arsenic and antimony in zinc smelting slag

Broussonetia papyrifera, Cryptomeria fortunei, Arundo donax, and Robinia pseudoacacia were planted on a zinc smelting slag site. The habitat conditions and spatial distribution of arsenic (As) and antimony (Sb) in slag were analyzed after seven years of restoration. The results showed that the pH, conductivity (EC), and moisture content of phytoremediated slag were lower than those of the control slag. The redox potential (Eh) and EC decreased with increasing slag depth. Phytostabilization significantly increased the contents of total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), available phosphorus (AP), and dissolved organic carbon (DOC) in slag. TN, AN, AP, and DOC in slag showed obvious surface polymerization. Phytostabilization increased the content of calcite and gypsum in the slag. As and Sb concentrations were significantly lower than control slag, with an average decrease of 651–844 and 422–693 mg·kg −1, respectively. Residual As and Sb in phytoremediated slag was the most present form, the proportion of which was higher than that in the control slag. The proportions of calcium-bound and aluminum-bound As and Sb were lower. The contents of arsenic and antimony in plants had lower levels and followed the order of roots > leaves > stems. As and Sb showed a strong positive correlation with pH, EC, moisture content, and a negative correlation with TN, TP, AN, AP, and DOC. In summary, phytostabilization significantly improved slag site conditions and reduce As and Sb available concentrations. Novelty statement Co-contamination of As and Sb is common in mining areas because of similar chemical properties. There are only few reports on the effects of matrix modification and phytoremediation (without additional soil cover) on the soil physicochemical properties, the spatial distribution, and the bioavailability of As and Sb in zinc slag with an alkaline pH. The research determined that phytostabilization significantly improved slag site conditions and reduce As and Sb available concentrations. The results obtained can be used as necessary information for the large-scale ecological restoration or vegetation reconstruction of zinc smelting slag yards.

Effects of Zinc Smelting Waste Slag Treated with Root Organic Acids on the Liver of Zebrafish (Danio rerio).

Vegetation reconstruction was widely adopted for the waste slag site. But the toxic elements may be made public from slag due to the organic acid secreted by plant roots, which will pollute the surrounding environment and harm human health. The purpose of the study was to evaluate the harm of toxic substances released from zinc (Zn) smelting waste slag to zebrafish. The effect was simulated by adding organic acid to slag, and the toxicity of the slag was evaluated through the enzyme activity, genetic toxicity, tissue sections of zebrafish liver tissue. The results showed that more heavy metals were made public from the slag, as the concentration of organic acids increased. Exposure to toxic substances for 14days, the antioxidant enzyme activities, termed as superoxide dismutase (SOD) and catalase (CAT), were significantly affected, which caused obvious malondialdehyde (MDA) accumulation. A comet assay revealed dose-dependent DNA damage in hepatocytes. Depending on the histopathological analysis, atrophy and necrosis of cells and increased hepatic plate gap were observed. The obtained results highlighted that toxic substances from slag may be deleterious to zebrafish.

Spatial distribution prediction of soil As in a large-scale arsenic slag contaminated site based on an integrated model and multi-source environmental data

Different prediction models have important effects on the accuracy of spatial distribution simulations of heavy metals in soil. This study proposes a model (RFOK) combining a random forest (RF) with ordinary kriging (OK), multi-source environmental data such as terrain elements, site environmental elements, and remote sensing data were incorporated to predict the spatial distribution of heavy arsenic (As) in soil of a certain large arsenic slag site. The predictions results of RFOK were compared with those obtained using the RF, OK, inverse distance weighted (IDW), and stepwise regression (STEPREG) models for assessment of prediction accuracy. The results showed that arsenic pollution was widely distributed and the center of the site, including arsenic slag stacking area and production area were seriously polluted. The overall spatial distribution of arsenic pollution simulated by the five models was similar, but the IDW, RF, OK, and STEPREG showed less spatial variation of soil pollution, while RFOK simulation can better express the characteristics of details in change. The cross-validation results showed that RFOK had the lowest root-mean-square error (RMSE), mean absolute error (MAE), and mean relative error (MRE) relative to the other four models, followed by RF, OK, IDW, and STEPREG. The RMSE, MAE and MRE of RFOK decreased by 62.2%, 64.3% and 68.7%, respectively, relative to the RF model with the second highest accuracy. Compared with the traditional spatial distribution prediction model, the RFOK model proposed in this study has excellent spatial distribution prediction ability for soil heavy metal pollution with large spatial variation characteristics, which can fully explain the nonlinear relationship between pollutant content and its environmental impact elements.

Ancient Mining and Metallurgy Activities in Mazayjan District, Fars Province

Ancient Mining and Metallurgy Activities in Mazayjan District, Fars Province

Study on Test and Detection Method of Mechanical Properties of Heavy Metal Contaminated Soil

ABSTRACT Heavy metal pollution in soil has an increasingly serious impact on the ecological environment, quality of agricultural and livestock products, and healthy living. Researches on detection methods and remediation technologies for heavy metal contaminated soil have received widespread attention. In this paper, the conventional mechanical properties and viscoelastic properties of heavy metal (cadmium, chromium, lead, zinc) contaminated soils were experimentally studied in combination with heavy metal pollution for agricultural soil. Compressive stress and strain, compressive strength, compressive modulus, and other indices of compressive mechanical properties, shear strength, shear modulus, and other indices of shear mechanical properties, bending strength, bending stiffness, elastic modulus, and other indices of bending mechanical properties in four metal contaminated soil samples and control group at different moisture contents were tested. Because viscoelastic plasticity and time effect soil, the correlation between creep parameters such as delay elastic modulus, viscosity coefficient, and heavy metal content were studied. The difference between the mechanical properties of the heavy metal contaminated soil sample and the control soil sample was analyzed, and a significant difference index was selected, and a discriminative model for heavy metal contaminated soil was proposed through multiple logistic regression analysis. The discriminative model was used to verify the heavy metal contaminated soils configured in the laboratory and contaminated soil retrieved from chromium slag site, and a detection method for expressing soil heavy metal pollution by using mechanical property parameters was explored to provide method reference for the detection of heavy metal contaminated soil.

Spatial Distribution characteristics and Ecological risk Assessment of heavy Metal As, Ba in soil of a Chemical Slag Field in Sichuan Province

45 boreholes were determined according to the situation of an industrial slag field in Sichuan Province. According to 10~20cm stratification as soil sampling, the content and characteristic distribution of heavy metal elements, such as barium (Ba), arsenic (AS) in soil, were determined, and the spatial distribution characteristics of As, Ba were studied by Geostatistics method. The pollution and ecological risk of As, Ba in the industrial slag site were analyzed by using the single factor index method, the Nemerow index method and the potential risk index evaluation. The results show that barium is the main pollution factor of waste residue, with an average value of 127576μg/L, which is mainly distributed in the range of 2.908~2667000 μg/L. The mean value of arsenic was 8.72 mg/kg, respectively.

Risk post-assessment and management of a waste slag site under extreme scenarios

The failure of waste slag is a disaster that impacting both environment and lives. In China, there are many waste slags after the engineering projects such as the construction of railway and road. Although the treatment of the waste slags obeys the regulations that the government have established, some accidents still happened. In order to ascertain the reason for the unexpected failure, the inverse analysis is needed to check the initial stability status and the level of potential damage of slag sites. The conventional failure probability of waste slag site is analyzed based on relevant factors that have considerable uncertainty and are difficult to quantify. Therefore, assuming that the failure of slag sites will occur under extreme scenarios, a methodological procedure of risk post-assessment and management under extreme scenarios is proposed in the paper, which indicates that risk management is necessary during the procedure of design, operation, and maintenance of the slag site. In this method, the Tsunami-Squares method was used to simulate the movement process of tailings sand due to the dam failure and generate hazard mapping with the intensity parameters (flow path and thickness). The integrated risk of economic loss, fatalities, and contamination to children and adults was considered in the paper. Following the As Low As Reasonably Possible principle, the F–N diagram was divided into five domains to represent four different risk acceptable conditions, and accordingly, the risk treatment measures were proposed respectively for waste slag sites. A risk management mode of “risk-sharing community” was presented that sparkplugged the representatives of multi-stakeholder to participate in the risk management. The proposed methodological procedure of risk analysis and management could provide effective supports to the decision-making of the design factors and the implementation of stabilization and monitoring of waste slag sites.