Heavy metals in soil from gangue stacking areas increases children health risk and causes developmental neurotoxicity in zebrafish larvae

Fluoride and acid enrichment in coal fire sponges in the Wuda coalfield, Inner Mongolia, Northern China

Coal fire sponges (CFSs) are a type of sponge-like contaminated soil bulge common in coal fire areas. However, the impacts of CFSs on the local environment are not yet understood. Thus, this study investigated soil samples from CFSs in the Wuda coalfield, Inner Mongolia, China, focusing on the acidity, sulfate, and fluorine content. The results showed that the CFSs were highly acidic, with an average pH of 0.76, and contained high levels of SO42- (257.29 × 103 μg/g), total fluorine (TF, 2011.6 μg/g), and water-soluble fluorine (WF, 118.94 μg/g), significantly exceeding those in the regional background soil and indicating that CFSs are a point source of heavy pollution. Soils in the 8000 m2 reclamation zone showed elevated acidity and high SO42- (129.6 × 103 μg/g), TF (1237.8 μg/g), and WF (43.05 μg/g) levels, which was likely the result of the weathering and dissemination of CFS. The CFS samples were rich in hydrogen fluoride, releasing 202.05 ppb of it when heated to 40 °C. Correlation analysis indicated that the acid sulfate soils in CFSs are likely caused by HSO4-/SO42-. Time-of-flight secondary ion mass spectrometry detected four characteristic ions (F-, H3O+, H2SO4+, and HSO4-) in all micro-domains of each sample, indicating that ionic fluorine compounds and sulfuric acid hydrate were found in the CFS samples. Sulfate minerals detected in CFSs included CaSO4, Fe2(SO4)3, CdSO4, NH4HSO4, and Na2SO4. Thus, the results identified CFSs as a transmission channel for contamination, with erosional surface soils as the carrier, for the first time. CFSs pose a serious threat of contamination, albeit over limited areas.

Life cycle assessment of coal mines of diverse scales over time in China

Coal mining has important detrimental effects on the environment and human health. By the end of 2022, China mined more than 4 billion tons of raw coal, and coal mining contributed to adverse environmental impacts. The objective of this work is to evaluate the environmental impacts emanated from coal mines in different periods (construction period, production period and closing period) and to find the relationship between coal mine scale and ecological impacts. This study uses coal mines that produce 0.45 Mt/a (considered a medium sized mine), 3 Mt/a and 8 Mt/a (both classified as large mines in this study) and a 12 Mt/a extra-large coal mine. Based on the time dimension, the mine life cycle was classified into construction, production and closing period, and the life cycle assessment method was used to conduct environmental assessment. The main influencing substances and key processes were tracked. The results indicated that mining engineering and gangue are the main factors affecting the construction and production periods of coal mines. Freshwater ecotoxicity, marine ecotoxicity, and human toxicity are the main environmental effects of coal produce, and they are mostly brought up by the release of hazardous elements like copper, chromium, zinc, nickel, and copper. Furan, formaldehyde, and chromium emissions during mine closure can be effectively reduced through environmental compensation, however coal mines' environmental compensation during mine closure is minimal. The environmental impact of coal mines producing 3 Mt and 8 Mt annually is minimal. The environmental impact of 0.45 Mt/a and 3 Mt/a coal mines is more prominent in the construction period. The pollutant discharge throughout the production phase, particularly the metal leaching discharge from gangue, needs to receive more attention from the 8 Mt/a and 12 Mt/a coal mines. Additionally, the larger the scale of coal mine production, the greater the proportion of the total environmental impact in the production stage.

Assessing the disparity: comparative toxicity of Copper in zebrafish larvae exposes alarming consequences of permissible concentrations in Brazil

Copper (Cu) is a naturally occurring metal with essential micronutrient properties. However, this metal might also pose increased adverse environmental and health risks due to industrial and agricultural activities. In Brazil, the maximum allowable concentration of Cu in drinking water is 2 mg/L. Despite this standard, the impact of such concentrations on aquatic organisms remains unexplored. This study aimed to evaluate the toxicity of CuSO4 using larval zebrafish at environmentally relevant concentrations. Zebrafish (Danio rerio) larvae at 72 hr post-fertilization (hpf) were exposed to nominal CuSO4 concentrations ranging from 0.16 to 48 mg/L to determine the median lethal concentration (LC50), established at 8.4 mg/L. Subsequently, non-lethal concentrations of 0.16, 0.32, or 1.6 mg/L were selected for assessing CuSO4 -induced toxicity. Morphological parameters, including body length, yolk sac area, and swim bladder area, were adversely affected by CuSO4 exposure, particularly at 1.6 mg/L (3.31 mm ±0.1, 0.192 mm2 ±0.01, and 0.01 mm2 ±0.05, respectively). In contrast, the control group exhibited values of 3.62 mm ±0.09, 0.136 mm2 ±0.013, and 0.3 mm2 ±0.06, respectively. Behavioral assays demonstrated impairments in escape response and swimming capacity, accompanied by increased levels of reactive oxygen species (ROS) and lipid peroxidation. In addition, decreased levels of non-protein thiols and reduced cellular viability were noted. Data demonstrated that exposure to CuSO4 at similar concentrations as those permitted in Brazil for Cu adversely altered morphological, biochemical, and behavioral endpoints in zebrafish larvae. This study suggests that the permissible Cu concentrations in Brazil need to be reevaluated, given the potential enhanced adverse health risks of exposure to environmental metal contamination.

Comprehensive study on the spatial distribution of heavy metals and their environmental risks in high-sulfur coal gangue dumps in China

The accumulation of coal gangue (CG) from coal mining is an important source of heavy metals (HMs) in soil. Its spatial distribution and environment risk assessment are extremely important for the management and remediation of HMs. Eighty soil samples were collected from the high-sulfur CG site in northern China and analyzed for six HMs. The results showed that the soil was heavily contaminated by Mn, Cr and Ni based on the Nemerow index, and posed seriously ecological risk depended on the geo-accumulation index, potential ecological risk index and risk assessment code. The semi-variogram model and ordinary kriging interpolation accurately portrayed the spatial distribution of HMs. Fe, Mn, and Cr were distributed by band diffusion, Ni was distributed by core, the distribution of Cu had obvious patchiness and Zn was more uniform. The spatial autocorrelation indicated that all HMs had strong spatial heterogeneity. The BCR sequential extraction was employed to qualify the geochemical fractions of HMs. The data indicated that Fe and Cr were dominated by residual fraction; Cu, Ni and Zn were dominated by reducible and oxidizable fractions; Mn was dominated by reducible and acid-extractable (25.38%-44.67%) fractions. Pearson correlation analysis showed that pH was the main control factor affecting the non-residue fractions of HMs. Therefore, acid production from high sulfur CG reduced soil pH by 2-3, which indirectly promoted the activity of HMs. Finally, the conceptual model of HMs contamination at the CG site was proposed, which can be useful for the development of ecological remediation strategies.

Effects of long-term herbaceous plant restoration on microbial communities and metabolic profiles in coal gangue-contaminated soil

The soil microbial diversity in the gangue accumulation area is severely stressed by a variety of heavy metals, while the influence of long-term recovery of herbaceous plants on the ecological structure of gangue-contaminated soil is to be explored. Therefore, we analysed the differences in physicochemical properties, elemental changes, microbial community structure, metabolites and expression of related pathways in soils in the 10- and 20-year herbaceous remediation areas of coal gangue. Our results showed that phosphatase, soil urease, and sucrase activities of gangue soils significantly increased in the shallow layer after herbaceous remediation. However, in zone T1 (10-year remediation zone), the contents of harmful elements, such as Thorium (Th; 1.08-fold), Arsenic (As; 0.78-fold), lead (Pb; 0.99-fold), and uranium (U; 0.77-fold), increased significantly, whereas the soil microbial abundance and diversity also showed a significant decreasing trend. Conversely, in zone T2 (20-year restoration zone), the soil pH significantly increased by 1.03- to 1.06-fold and soil acidity significantly improved. Moreover, the abundance and diversity of soil microorganisms increased significantly, the expression of carbohydrates in soil was significantly downregulated, and sucrose content was significantly negatively correlated with the abundance of microorganisms, such as Streptomyces. A significant decrease in heavy metals was observed in the soil, such as U (1.01- to 1.09-fold) and Pb (1.13- to 1.25-fold). Additionally, the thiamin synthesis pathway was inhibited in the soil of the T1 zone; the expression level of sulfur (S)-containing histidine derivatives (Ergothioneine) was significantly up-regulated by 0.56-fold in the shallow soil of the T2 zone; and the S content in the soil significantly reduced. Aromatic compounds were significantly up-regulated in the soil after 20 years of herbaceous plant remediation in coal gangue soil, and microorganisms (Sphingomonas) with significant positive correlations with benzene ring-containing metabolites, such as Sulfaphenazole, were identified.

Spatial distribution characteristics and risk assessment of soil heavy metal pollution around typical coal gangue hill located in Fengfeng Mining area

The pollution of heavy metals in soil caused by exposed coal gangue and its prevention and control has become a hot issue restricting the green mining of coal in China. Nemerow integrated pollution index (NIPI), potential ecological risk index (RI) and human health risk assessment model were used to evaluate the pollution and risk of heavy metals (Cu, Cr, As, Pb) in the soil around the typical coal gangue hill in Fengfeng mining area of China. The results show that: firstly, the accumulation of coal gangue leads to the enrichment of four heavy metals in the surrounding shallow soil, and NIPI and RI were 1.0-4.4 and 21.63-91.28, respectively. The comprehensive pollution level of heavy metals in soil reached the warning line and above, and the potential ecological risk level reached slightly and above. When the horizontal distance exceeded 300 m, 300 m and 200 m, respectively, the influence of coal gangue hill on the heavy metal content in shallow soil, the comprehensive pollution level of heavy metals and the potential ecological risk level basically disappeared. In addition, based on the potential ecological risk assessment results and main risk factors, the ecological risk configuration of the study area was divided into five categories: "strong ecological risk + As," "intermediate ecological risk + As + Cu," "intermediate ecological risk + As + Cu or Pb," "minor ecological risk + As + Cu" and "minor ecological risk + As + Cu or Pb." The hazard index (HI) and total carcinogenic risk (TCR) of shallow soil polluted by heavy metals in the study area were 0.24-1.07 and 0.41 × 10-4-1.78 × 10-4, respectively, which posed non-carcinogenic and carcinogenic risks to children, but the risks were controllable. This study will help to take strategic measures to accurately control and repair the heavy metal pollution in the soil around the coal gangue hill and provide a scientific basis for solving the safe use of agricultural land and realizing the construction of ecological civilization.

Evaluation of the developmental effects of a glyphosate-based herbicide complexed with copper, zinc, and manganese metals in zebrafish

The use of glyphosate-based herbicides (GBH) has increased dramatically, being currently the most used herbicides worldwide. Glyphosate acts as a chelating agent, capable of chelate metals. The synergistic effects of metals and agrochemicals may pose an environmental problem as they have been shown to induce neurological abnormalities and behavioural changes in aquatic species. However, as their ecotoxicity effects are poorly understood, evaluating the impacts of GBH complexed with metals is an ecological priority. The main objective of the study was to evaluate the potentially toxic effects caused by exposure to a GBH (1 μg a.i. mL^-1), alone or complexed with metals (Copper, Manganese, and Zinc (100 μg L^-1)), at environmentally relevant concentrations, during the early period of zebrafish (Danio rerio) embryo development (96 h post-fertilization), a promising model for in vivo developmental studies. To clarify the mechanisms of toxicity involved, lethal and sublethal development endpoints were assessed. At the end of the exposure, biochemical and cell death parameters were evaluated and, 24 h later, different behavioural responses were assessed. The results showed that metals induced higher levels of toxicity. Copper caused high mortality, low hatching, malformations, and changes in biochemical parameters, such as decreased Catalase (CAT) activity, increased Glutathione Peroxidase (GPx), Glutathione S-Transferase (GST), reduced Glutathione (GSH) and decreased Acetylcholinesterase (AChE) activity, also inducing apoptosis and changes in larval behaviour. Manganese increased the activity of SODs enzymes. Zinc increased mortality, reactive oxygen species (ROS) levels, superoxide dismutase activity (SODs) and caused a decrease in AChE activity. Embryos/larvae exposed to the combination of GBH/Metal also showed teratogenic effects during their development but in smaller proportions than the metal alone. Although more studies are needed, the results suggest that GBH may interfere with the mechanisms of metal toxicity at the biochemical, physiological, and behavioural levels of zebrafish.

Effects of BPZ, BPC, BPF, and BPS Exposure on Adult Zebrafish (Danio rerio): Accumulation, Oxidative Stress, and Gene Expression

As substitutes for bisphenol A (BPA), bisphenol analogs (BPs) have been found to cause endocrine disorders and induce toxic effects. The objective of this study was to evaluate the bioaccumulation and subacute toxicity of bisphenol Z (BPZ), bisphenol C (BPC), bisphenol F (BPF), and bisphenol S (BPS) to zebrafish. Five-month-old zebrafish were exposed to 1/100 LC₅₀, 1/50 LC₅₀, and 1/10 LC₅₀ of BPZ, BPC, BPF, and BPS for 13 days, respectively. Bioaccumulation, oxidative stress, and related mRNA expression in zebrafish tissues were measured on days 1, 7, and 13. After exposure, the four kinds of BPs all resulted in the accumulation of concentration and lipid peroxidation in zebrafish tissues to varying degrees. BPZ and BPC had the highest bioaccumulation level and had the greatest influence on malonic dialdehyde (MDA). In addition, the enzyme activities of superoxide dismutase (SOD), peroxidase (POD), glutathione peroxidase (GSH-PX), and the content of glutathione (GSH) in zebrafish tissues were also affected at different levels. However, the enzyme activities of SOD and POD were inactivated in zebrafish exposed to a high concentration of BPC. Further studies showed that BPs exposure down-regulated the transcription level of sod but up-regulated the relative expression levels of cat and gpx. The mRNA relative expression level of erα was not significantly changed, while the mRNA relative expression level of erβ₁ was significantly down-regulated except under BPS exposure. These results indicate that BPZ, BPC, and BPF significantly affect the expression level of the estrogen receptor (ER) in zebrafish tissues. Overall, the results suggest that exposure to waterborne BPs can cause severe oxidative stress and tissue damage in adult zebrafish that is not sufficient to kill them after 13 days of waterborne exposure. The toxicity of BPs to organisms, therefore, should be further analyzed and evaluated.

Risk assessment and early warning of the presence of heavy metal pollution in strawberries

Heavy metal pollution is a major threat to agricultural produce and it can pose potential ecological risks which subsequently impacts on human health. Strawberries are an economically important produce of China. The intrinsic link of heavy metal pollution risk in the soil-strawberry ecosystem is of concern. In this study, the pollution index of heavy metal pollutants in farmlands of different provinces were evaluated, and the results showed significantly high levels of cadmium. In addition, Nemerow integrated pollution index analysis showed that low-pollution farmlands only accounted for 14.07% of the total arable land area. Then, the transfer factors were used to calculate the migration of heavy metals from the soil into strawberries. The results showed that cadmium and nickel were relatively high in strawberries from the Guangxi province. Similar results were found for mercury in Jiangxi Province. The pollution index of single food pollution also showed that mercury in strawberries from Jiangxi Province was at a moderate pollution level. The comprehensive pollution index indicated that heavy metal pollution in strawberries in Central China may be severe. In addition, spatial clustering analysis showed that cadmium, chromium, lead, arsenic and zinc in strawberries had significant hotspot clustering in central, south and southwest China. Finally, our studies also suggested that the risk of carcinogenic and non-carcinogenic diseases was higher in the (2, 4] years age group than in other age groups. People in Yunnan Province were also found to have a higher non-carcinogenic risk than those in other provinces and cities in China. This study provides a comprehensive view of the potential risks of heavy metal contamination in strawberries, which could provide assistance in the design of regulatory and risk management programs for chemical pollutants in strawberries, thus ensuring the safety of consumption of these edible fruits.

Coupling effects of mineral components on arsenic transformation during coal combustion

Exploring arsenic (As) transformation during coal combustion is beneficial for reducing its pollution. Herein, combustion experiments were developed at 1100-1300 °C in a fixed-bed experimental system with 25 types of coal samples. The occurrences of As in coal and combustion products were characterized. All the original forms of As in coal were found to be unstable during combustion. As retained in ash existed as water-soluble and ion-exchangeable and residual forms, but only as residual form at combustion temperature above 1200 °C. The distribution of As in gaseous and solid combustion products varied widely by coal types, which resulted from the coupling effects of multi-minerals in coal. Co-combustion experiments were conducted using As model compounds and pure minerals, by which the interaction of Ca, Fe, Si and Al minerals to retain As was elucidated. The As transformation during coal combustion was primarily attributed to the coupling action of Ca, Fe, Si and Al minerals in coal. As a result, As was retained as Ca-Si-Al-As and Fe-Si-Al-As composite salts in the ash, which have little environmental hazard. Utilizing the coupling effects of multi-minerals during combustion help reduce As pollution from coal-fired plants.

Zinc in soil reflecting the intensive coal mining activities: Evidence from stable zinc isotopes analysis

In the mining area affected by coal mining activities for a long time, heavy metal Zn pollution poses a serious threat to soil quality and human health, and direct evidence showing the relationship between Zn accumulation mechanism in soils and mining activities is lacking. In this study, the Zn content and isotopes composition (δ⁶⁶Zn) from soil and environmental samples around mining area were determined and analyzed to clarify the Zn characteristics in soil. Moreover, the distribution and source of Zn content in soil of mining area were analyzed by mathematical statistics, correlation analysis and isotope mass mixing model. The results showed that: (1) the Zn content in soil ranged from 95 to 327 mg·kg^-1 (mean: 233 mg·kg^-1), exceeding the control point and the soil background value of Anhui Province; (2) the results of Zn isotope analysis showed that Zn in soil mainly derived from the wind dispersion input of fine particles in gangue and fly ash, followed by the natural weathering of parent material; (3) isotopic mass mixing model can be used to distinguish the contribution of anthropogenic and natural Zn sources. Mining input was the main contribution source of Zn in soil (mean: 67%), followed by natural background (mean: 33%). The employment of Zn isotopes can effectively evaluate the impact of anthropogenic and natural long-term processes on Zn in the soil of the mining area, and provide important information for the formulation of soil metal pollution control measures.

Study on the distribution characteristics and ecological risk of heavy metal elements in coal gangue taken from 25 mining areas of China

The long-term, high-yield production of coal has resulted in the large-scale accumulation of coal gangue on the ground surface, which causes serious environmental problems. Therefore, clean and environmental treatment of coal gangue is urgently needed. In this study, the inductively coupled plasma mass spectrometer and atomic fluorescence spectrometer were used to test the background values of ten heavy metals in coal gangue taken from 25 coal mines across China; the average content, distribution characteristics, and genesis of heavy metals in these coal gangue were investigated, and the ecological risk of heavy metals in coal gangue in different regions and different geological ages was analyzed and tested. The results show that the average contents of Hg, Pb, Cd, Cr, As, Cu, Zn, Mn, Se, and Be in the coal gangue are 0.081, 17.444, 0.234, 63.329, 2.658, 43.697, 59.290, 427.460, 1.205, and 1.819 mg/kg, respectively; the enrichment sequence of heavy metal elements of coal gangue in geographical areas and geological ages are ordered as follows: South China region > North China region > Northeast China region > Northwest China region, P₂ > C₂-P₁ > K₁ > J_1-2 > E-N. The results also show that Hg has a strong pollution risk, Cd has a moderate pollution risk, and the remaining eight heavy metals have minor pollution risks, and the overall ecological risk indices (RI) of heavy metals in different geographical areas are ordered as [Formula: see text] (South China) > [Formula: see text] (North China) > [Formula: see text] (Northeast China) > [Formula: see text] (Northwest China). Moreover, the hydrothermal process occurring in unique sedimentary environments during the formation period is a key factor for the regional heavy metal enrichment in coal gangue.

The immunotoxicity of Cd exposure to gypsy moth larvae: An integrated analysis of cellular immunity and humoral immunity

Heavy metal exposure-triggered growth retardation and physiology disorder in phytophagous insects have been widely understood, but only a few studies have investigated its immunomodulatory effects on herbivorous insects. Here, the innate immunity of gypsy moth (Lymantria dispar) larvae under Cd stress was evaluated by integrating cellular and humoral immunity, and the immunomodulation mechanism of Cd stress was further understood by the proteomics analysis of larval hemolymph. Our results showed that the total hemocyte count, as well as phagocytic, encapsulation and bacteriostatic activity, of hemolymph in gypsy moth larvae exposed to Cd stress was significantly lower than that in un-treated larvae. Further proteomic analysis revealed that Cd exposure may reduce the total hemocyte count in larval hemolymph by inducing endoplasmic reticulum pathway-mediated hemocyte apoptosis, thereby causing the collapse of cellular immunity in gypsy moth larvae. In addition, the transcriptional level of signal transduction genes (IMD, Toll, Relish, JAK and STAT) and antimicrobial peptide genes (cecropin and lebocin), as well as the protein abundance of pattern recognition receptors (PGRP and GNBP3) in the Toll, IMD and JAK/STAT signaling pathways was significantly decreased in Cd-treated larvae, clearly implying an immunosuppresive effect of Cd stress on pathogen recognition, signal transduction and effector synthesis of humoral immunity in gypsy moth larvae. Taken together, these results suggest that Cd exposure decreases both cellular immunity and humoral immunity of gypsy moth larvae, and provides a new entry point for systematically and comprehensively unraveling the heavy metal pollutants-caused immunotoxicity.

Preparation of Poly Aluminum-Ferric Chloride (PAFC) Coagulant by Extracting Aluminum and Iron Ions from High Iron Content Coal Gangue

Poly aluminum-ferric Chloride (PAFC) is a new type of high efficiency coagulant. In this study, high iron type gangue is used as a main raw material. It is calcined at 675 °C for 1 h and 3% CaF2 is added to the calcined powder and reacted with 20% hydrochloric acid at 93 °C for 4 h. The leaching ratio of aluminum ions is 90% and that of iron ions is 91%. After Fe2+ ions are oxidized in the filtrate, CaCO3 is used to adjust the pH of the filtrate to 0.7. The microwave power is adjusted to 80 W and the filtrate is radiated for 5 min. After being aged for 24 h, PAFC product is obtained. The prepared PAFC is used to treat mine water and compared with the results of PAC and PAF, the turbidity removal ratio of PAFC is 99.6%, which is greater than 96.4% of PAC and 93.7% of PAF. PAFC is a mixture with different degrees of polymerization. It demonstrates that extracting aluminum and iron ions from high iron content gangue to prepare PAFC by microwave is efficient and feasible.

Research on the co-pyrolysis of coal gangue and coffee industry residue based on machine language: Interaction, kinetics, and thermodynamics

Co-pyrolysis technology of urban solid waste and biomass has broad application prospects in alleviating energy crisis and environmental pollution. In this study, thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR) was used to study the co-pyrolysis characteristics of coal gangue (CG) and coffee industry residue (CIR). CG and CIR were uniformly mixed according to the mass ratios of 1: 0, 7:3, 5:5, 3:7, and 0:1. Then the samples were heated and pyrolyzed in an atmosphere with a nitrogen flow rate of 60 mL/min. As the proportion of CG increased, the comprehensive pyrolysis index (CPI) showed an exponential decrease. FTIR detected that the gas produced by pyrolysis of CG-CIR contained hydroxyl compounds, hydrocarbons, CO₂, CO, Phenols, and NH₃. CG-CIR co-pyrolysis had obvious interaction. By using Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods, the relationship between activation energy (E_α) and kinetic parameters and conversion degree was studied. Principal component analysis (PCA) was used to determine the principal reaction of CG-CIR pyrolysis. ANN 21 was the best model for predicting the pyrolysis of CG-CIR.