Unveiling the Influence of Antimony Substitution on the Surface Properties and Adsorption Behavior of Ferrihydrite: From Molecular Mechanisms to Environmental Implications.

Antimony(V) substitution is common in secondary ferrihydrite, especially in mining areas and tailings. However, its impact on the adsorption behavior of ferrihydrite is still unclear. Therefore, this study investigated the influential mechanisms of Sb(V) substitution on the lattice structure and surface properties of Sb-substituted ferrihydrite (SbFh), and its adsorption of coexisting Sb(OH)6-. Antimony(V) is substituted at Fe1 sites and is primarily distributed on the surface. Substitution has opposing effects on the outer- and inner-sphere complexation of Sb(OH)6-. On one hand, substituted-Sb(V) transfers more positive charges to ≡FeOH, reducing the number of H bonds. Subsequently, the charge saturation of ≡FeOH decreases, surface charge increases, and outer-sphere complexation is promoted. On the other hand, the elevated bond valence of Sb-O increases charge saturation of ≡FeOH, reducing the charge capacity that ≡FeOH can accommodate from inner-sphere complexes. Thus, inner-sphere complexation is inhibited. Inner-sphere complexation plays a more important role, and Sb(OH)6- adsorption is inhibited. Additionally, the primary complexation modes of Sb(OH)6- transform from bidentate to monodentate complexation. This research has important implications for understanding the environmental behavior of ferrihydrite, as well as the fate and bioavailability of antimony in mining areas and tailings.

Distribution, sources, and risk assessment of polycyclic aromatic hydrocarbons in surface soils and plants from industrial and agricultural areas, Junggar Basin, Xinjiang.

The contamination characteristics of Polycyclic Aromatic Hydrocarbons (PAHs) in different environmental functional areas are different. In this study, the contamination of PAHs in soils and common plants in typical mining and farmland areas in Xinjiang, China, was analyzed. The results showed that the contamination levels of PAHs in mining soils were significantly higher than those in farmland soils, and the mining soils were dominated by 4-5-ring PAHs and farmland soils by 3-4-ring PAHs. Analysis of their sources using a positive definite factor matrix model showed that PAHs in mining soils mainly originated from coal and natural gas combustion, and transportation processes; while farmland soils mainly came from biomass and coal combustion, and fossil fuel volatile spills. The cancer risk of PAHs in soils was evaluated using a combination of the Monte Carlo and the lifetime carcinogenic risk models, and the results showed that the overall level of cancer risk for mining soils was higher than that for farmland soils, and can put some people in high risk of cancer. For plant samples, except for individual crop samples, the contamination levels of mining plants and crops were similar, with 4-5-ring PAHs dominating in desert plants in mining areas and the highest proportion of 3-ring PAHs in crops in agricultural fields, and PAHs in both plants were mainly from biomass and coal combustion. The results of correlation analysis showed that 2-ring PAHs in crop roots were significantly positively correlated with it in corresponding soils, and some high-ring PAHs in crop leaves were significantly negatively correlated with it in corresponding soils. Therefore, there were significant differences in the pollution characteristics of PAHs in soils and common plants in mining and agricultural areas. Human health risks and ecological risks are mainly concentrated in mining areas, and appropriate intervention measures should be taken for pollution remediation.

Varieties of P fractions in biochar-amended reconstructed soils as impacted by freeze-thaw interference.

With low cost and stable chemical properties, biochar has great potential in environmental pollution control and improving soil quality. Reusing tailings slag to reconstruct soil ecosystems and applying amendments such as biochar to enhance soil quality are significant for restoring waste mine lands. Phosphorus (P) as the restrictive nutrition element for plant growth is easily affected by freeze-thaw cycles (FTCs). However, effective information about FTCs on P dynamics in biochar-amended reconstructed soil is scanty. To further understand the effect of FTCs on P in reclaimed mine soils, three reconstructed soils composed of equal brown soil and tailings slag with the respective application of no amendment, 5% biochar and 5% powder both derived from Gleditsia japonica shells (GS), were prepared to evaluate P fraction changes after FTCs. The results indicated that GS biochar increased soil pH, total organic matter (TOM), and moisture content (MC). GS biomass had a similar impact on TOM and MC but decreased soil pH. The two agricultural amendments increased active P and microbial biomass P (MBP) by 46.13%-101.63% and 162.8%-185.7%, which might be largely contributed by soil organic matter and moisture. FTC numbers (0, 3, 6, 10, 15) significantly decreased MBP contents and slightly converted non-labile P into labile fractions while FTC temperature (-20∼5 °C and -10∼5 °C) hardly influenced soil P behavior. In addition, GS conditioners simultaneously enhanced available P content and P fixation potential by soil under FTCs.

Interplays between plants and environmental factors determine pullout resistance on different revegetated slopes in mining areas.

Plant roots play a crucial role in enhancing soil stability and protecting slopes during ecological restoration, particularly in mining areas where external-soil spray seeding is employed. However, the relationship between plant root pullout resistance and environmental factors on different types of slopes remains unclear. In this study, we investigated the interactions between the pullout resistance of a dominant species, Artemisia gmelinii, and environmental factors on three slope types (rocky, geotechnical, and soil) using multi-group structural equation modeling. Our findings reveal that the pullout resistance of plant roots was strongly influenced by various factors, including but not limited to biological factors such as plant height and biomass. It showed a positive correlation between soil silt content and soil nutrient levels. Notably, the pullout resistance on soil slopes was significantly higher than on rocky slopes. Furthermore, the impact of soil nutrients and texture on pullout resistance was more pronounced on geotechnical and soil slopes compared to rocky slopes. Multi-group structural equation modeling highlighted that among all environmental factors, slope gradient and underground biomass had the most significant influence on pullout resistance across all slope types. Specifically, slope gradient had a greater effect on soil slopes, whereas underground biomass played a more prominent role on rocky and geotechnical slopes. Overall, our study suggests that when implementing external-soil spray seeding in mining areas, it is crucial to consider the interplay between plant roots and environmental factors, including slope properties. This holistic approach is crucial for maximizing the effectiveness of plants in slope protection during eco-engineering projects.

Atypical caudal regression syndrome with lumbar agenesis, hypoplastic sacrum without sacroiliac joints in the eastern Democratic Republic of Congo: a case report.

The agenesis of any segment of the lower spinal column referred to as "caudal regression syndrome" (CRS) is a rare congenital defect of the spine. This malformation is characterized by the absence of some or the entire lumbosacral vertebral segment. Etiological factors remain unknown. We report an atypical caudal regression syndrome with lumbar agenesis, disconnected from the remaining hypoplastic sacrum, in the Eastern part of the Democratic Republic of Congo (DRC).An 11-month-old female infant with no particular fetal or maternal history presented limb weakness with flexed knees and flanges in the popliteal fossae, sphincter atony, and a sensation of emptiness on palpation in the lumbosacral region. A 3D CT scan of the spine showed the absence of the lumbar spine and disconnection of the upper segment of the thoracic spine from the hypoplastic sacrum. We noted also the absence of the sacroiliac joints bilaterally and an unusual trigonal shape of the iliac bones. MRI and sonographic examination are required in the investigation of the disease. The management is multidisciplinary and depends upon the degree of the defect. Spine reconstruction has proven to be a valuable management technique but has many complications. We wanted to draw the medical world's attention to the existence of this extremely rare malformation in the east of the Democratic Republic of Congo, a mining area.

Pollution characteristics and source identification of farmland soils in Pb-Zn mining areas through an integrated approach.

Long-term mining activities have caused serious heavy metals contamination of farmland soils. In this study, we investigated the concentrations, distributions, accumulations, potential ecological risk, and sources of eight heavy metals in farmland soils of Pb-Zn mining areas. According to the soil standard GB15618-2018, Cd was the most contaminated, followed by Pb and Zn. The geo-accumulation index showed that Pb, Zn, Cd, and Hg accumulated seriously. The potential risk index indicated that Cd, Hg, and Pb were the main environmental risk elements. An integrated approach combining multivariate statistical analysis, PMF, and GIS mapping was used to analyze the sources of heavy metals. Four main sources were identified and quantified: (1) mining activities source, the main source of Cd (71.09%) and Zn (61.88%); (2) agricultural activities source, dominated by Hg (73.01%); (3) atmospheric deposition sources, with Pb (85.11%) as the main contributor; (4) natural source, characterized by Cr (72.96%), Ni (66.04%), As (55.98%) and Cu (37.70%). This study would help us understand the pollution characteristics and sources of farmland soils in mining areas and provide basic information for the next step of pollution control and remediation.

Distribution dynamics and descriptive statistical analysis of radionuclides in the farmland soils near mining areas in Southwestern Nigeria.

Human exposure to ionizing radiation in the environment is mainly due to naturally occurring radionuclides in the soils, building materials and rocks, but the level may vary depending on the anthropogenic activities prevalent in each location. Presently, in Nigeria, there are concerns due to environmental health implications of all sorts of mineral mining and processing spreading across the southwestern states of the country. This work determines the activity concentrations of naturally occurring radionuclide materials (NORMs) in the farmland soil with the aim of evaluating the radiation hazards. A total of 200 composite soil samples were taken from five states in the southwest of Nigeria, close to active mining sites at the root (0.2 m) and at deep planting zones (0.5 m) for analysis by gamma-ray spectrometry using NaI(Tl) detector. The activity concentrations of natural radionuclides in the composite soil samples were determined to vary in the order of 40 K > 232Th > 226Ra/238U for all locations. In contrast to the other locations, Olode and Igbokoda had average radium equivalent activities (Raeq) to be 1.6 and 1.8 times, respectively, higher than the reference limit of 370 Bqkg-1. The estimated excess life cancer risk values were lower than the 0.29 × 10-3 global average value for soil by United Nations on Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) and International Commission on Radiological Protection (ICRP). Negative and low skewness values of 0.61 and 1.20 were obtained for 40 K in Itagunmodi, and also 0.47 and 0.66 for 232Th were obtained in Sagamu. The kurtosis analysis of the activity concentrations was low and negative for soil at Itagunmodi for 40 K and 226Ra/238U; Olode for 40 K and 232Th; and Igbokoda for 226Ra/238U and 232Th where mining activities are commonly practiced. The variation in the results has been attributed to different agriculture practices and artisanal mining operations in each location.

Effectiveness of common macrophytes for phytoremediation of hexavalent Cr prevalent in chromite mining areas.

Hexavalent chromium Cr(VI) is carcinogenic. To reduce Cr(VI) toxicity, a study was undertaken to assess the effectiveness of common macrophytes in the range of Cr concentration prevalent in chromite mining areas at Sukinda, Odisha, India. The metal varied from 0.09 to 2.14 mg/L during 2016 - 2019 and indicated that ≅70% waterbodies are contaminated with Cr(VI). Phytoremediation experimentation using five common macrophytes resulted in Pistia stratiotes, Salvinia minima and Ipomoea aquatica as suitable species by remediating 57 to 100% Cr(VI) from 0.2 to 1.0 mg/L within 54 days. S. minima had then found to remove 1 to 1.8 and 1.6 to 2.8 times more Cr (total) than P. stratiotes and I. aquatica respectively from a level of 0.5 to 2.5 mg/L Cr(VI) within 49 days. Irrespective of plant-duration, P. stratiotes excelled over S. minima by 59 to 68% and I. aquatica by 55 to 89% in BCF value. S. minima thus proved best by removing maximum Cr per unit time while the combination of S. minima and P. stratiotes would have promise in respect of generating low volume of remediated biomass in phytoremediation of Cr(VI).Novelty statementMacrophytes differ in their response to remove metal, screening against a given metal concentration suggests the suitable species and testing signifies their effectiveness of remediating metal from contaminated sources.

Risk assessment of cadmium intake via food among residents in the mining-affected areas of Nandan County, China.

This study investigated the dietary structure, Cadmium (Cd) contents in foods and exposure to Cd through diets of the residents in the mining-affected areas of Nandan County in summer 2013 (July to August) and winter 2014 (November to December). The weighing of foods and the chemical analysis of foods were applied to determine the dietary structure, and the concentration of trace element Cd in the diets, respectively, of the residents in the mining-affected areas (Chehe town, Dachang town, and Zhanglao town) and a control area (Liuzhai town), and subsequently the Cd exposure from the diets was estimated. In the mining-affected areas, the geometric mean of Cd in rice and rice products was the highest (0.29 µg/g) among all food types, and it exceeds the value of 0.2ug/g from the China Food Safety National Standard for Maximum Levels of Contaminants in Foods (GB2762-2017). The Cd contents in rice and rice products, vegetables, and beans in the mining-affected areas were significantly higher than those in the control area. The estimated daily food intakes of Cd in the mining-affected areas were higher than the intake in the control area. The THQ in the mining-affected areas of Chehe town, Dachang town, and Zhanglao town was 3.03, 2.31, and 3.27, respectively. All of which were higher than the value of 1.44 in the control area. Thus, the high level of dietary cadmium intakes of residents in this area deserves our attention.

Are the soils and vegetation of a forest close to tailings ponds affected by metals and arsenic?

This study aimed to determine the transfer of metals (Cd, Pb and Zn) and As to a Mediterranean forest close to five tailings ponds in Cartagena-La Union mining district (SE Spain). In addition, the effect of the rhizosphere of two native plant species, Olea europaea (OE) and Pistacia lentiscus (PL), on soil properties and chemical speciation of metal(oid)s was evaluated. Results showed there was no influence of the rhizosphere in the total concentration of metal(loid)s in soil, decreasing as Pb > Zn > As > Cd. Chemical partitioning revealed that only Cd and As can be considered hazardous, with a high percentage of these elements in the soil-labile fractions (20-40%). The accumulation in vegetal tissues was only high for Pb in PL roots, which makes it a suitable species for phytostabilization. Additionally, translocation factors showed transfer of Pb and Zn in OE, and Zn in PL to aerial parts, although no toxicity evidences for plants or animals were found. Finally, soil properties affected metal(loid)s accumulation in plants. The OE species was related to soil-labile metal(loid) fractions and pH, total N, organic carbon and silt content. The PL species were associated with immobilized metal(loid) fractions, sand content, electrical conductivity and total concentrations of As, Cd and Pb. Hence, mining activity has affected native adjacent soils, with accumulation of metals in plant species, although translocation was low, likely due to physiological strategies of the studied species to protect themselves against hazardous elements, and to the high soil pH, which limits metals' mobility.

Molybdenum contamination dispersion from mining site to a reservoir.

This study was conducted to assess heavy metals in the overlying water and sediments of Luhun Reservoir, Henan Province, China, which is positioned downstream from a molybdenum (Mo) mining area. The pollution indexes indicated that deposition of all metals may have been affected by the mining area. The single element pollution factor (Pi) of Mo was the highest among all heavy metals, with a mean value of 2.05. However, the sediments were subject to long-term accumulation of metals, particularly Mo, Cd, Pb, and Zn, which originated from anthropogenic sources. The mean individual element potential ecological risk index values for Cd were above 385, while the mean value comprehensive potential ecological risk index was 465, which indicates a high ecological risk. Moreover, the enriched heavy metals had different spatial distributions in the Luhun Reservoir sediments. Finally, Pearson correlation analysis indicated that the Pb was mainly affected by different anthropogenic sources and had no relationship with other metals, which suggests that the influence of mining area on heavy metal concentrations in the reservoir is difficult to disentangle.

Spatial and temporal distribution of Mo in the overlying water of a reservoir downstream from mining area.

This study aimed to evaluate the spatial and temporal variations of molybdenum (Mo) in the downstream water body of a Mo mine during three hydrologic periods (wet, dry and medium seasons). The physical properties in Luhun Reservoir reflected seasonal variations in different hydrological periods. The redox potential (ORP) and dissolved oxygen (DO) increased in the dry season. The concomitant decrease in temperature (T), conductivity (COND) and total dissolved solids (TDS) were lowest in the wet season. The pH value did not change significantly during the three hydrologic periods. The distribution of Mo in the dry season was high in upstream and low in downstream areas, which was significantly different from that of the wet and medium seasons. The total Mo concentration in wet (150.1 µg/L) and medium season (148.2 µg/L) was higher than that in the dry season, but the TDS (288.3 mg/L) and the percentage dissolved Mo (81.3%) in overlying water was lowest in the wet season. There was no significant relationship between the dissolved Mo and the total Mo with TDS. In the dry season, the mean total Mo concentration was 116.3 µg/L, which was higher than the standard limit value (70 µg/L) for drinking water (US EPA-United States Environmental Protection Agency recommended value 40 µg/L). Non-point source pollution is the main characteristic of mining area pollution, which was closely related to rainfall. Thus, the Luhun Reservoir contains substantial Mo pollution, which was a significant concern given that it is used as a source of drinking and irrigation water.

Monte Carlo simulation-based probabilistic health risk assessment of metals in groundwater via ingestion pathway in the mining areas of Singhbhum copper belt, India.

Probabilistic health risk assessment was conducted for metal exposure through groundwater in mining areas of Singhbhum Copper Belt, India. The concentrations of metals showed notable spatial variation exceeding drinking water standards at some of the locations. Hazard Quotient revealed that chronic risks to the local population were largely contributed by Mn, Co and As. The 95th percentiles of Hazard Index (HI) calculated using Monte Carlo simulations showed that the HI for male, female and child populations was 2.87, 2.54 and 4.57 for pre-monsoon, 2.16, 1.88 and 3.49 for monsoon and 2.28, 2.02 and 3.75 for post-monsoon seasons, respectively. The Hazard Indices indicated that amongst the populations, risk was greater for child population and considering the seasons the risk was higher during the pre-monsoon season. The sensitivity analysis suggested that concentration of metals in groundwater and exposure duration were 2 most influential input variables that contributed to the total risk.

Human health risk assessment due to metals in cow's milk from Singhbhum copper and iron mining areas, India.

The concentration of Al, As, Ba, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se and Zn were determined in the milk collected from the locally rearing cows from the vicinity of copper mining areas of East Singhbhum and iron mining areas of West Singhbhum using inductively coupled plasma-mass spectrometry for a risk assessment and source apportionment study. Principal component analysis suggested both natural and anthropogenic activities as causative sources of metals in the milk. The hazard indices ranged from 0.26 to 0.89 with a mean of 0.56 in the iron mining areas and 0.29-1.89 with a mean of 1.17 in the copper mining areas due to ingestion of milk, which indicated that the risk is negligible in the iron mining areas while there is an appreciable risk to the health of consumers of milk in the copper mining areas.

The use of a geostatistical model supported by multivariate analysis to assess the spatial distribution of mercury in soils from historical mining areas: Karczówka Mt., Miedzianka Mt., and Rudki (south-central Poland).

For the purpose of this study, 181 soil samples were collected from three post-mining areas (Miedzianka Mt. (62), Karczówka Mt. (61), and Rudki (58)) in the Holy Cross Mountains, south-central Poland. Collected samples were dried, disaggregated, and digested in a closed microwave system. All solutions were analyzed for Hg concentrations with cold vapor-atomic absorption spectroscopy (CV-AAS) technique using a continuous flow vapor accessory. The average Hg concentrations and the upper limits of geochemical background (UBG) were as follows: Miedzianka Mt. Hg 0.501 mg kg-1, UBG 0.312 mg kg-1; Karczówka Mt. Hg 0.150 mg kg-1, UBG 0.180 mg kg-1; Rudki area Hg 0.216 mg kg-1, UBG 0.193 mg kg-1. The use of a spatial distribution map of mercury concentrations integrated with computed geochemical factors and results of cluster analysis showed a direct relationship between mercury contents and mining activity conducted in these areas. Only in the case of Miedzianka Mt., this relationship was visible and probably resulted from the presence of tennantite (Cu,Fe)12As4S13 in soil samples, which was also confirmed with the factor analysis. Higher Hg concentrations in soil samples from Karczówka Mt. and Rudki resulted from the presence of clay and other secondary minerals that increase the mercury adsorption from atmospheric deposition. Fossil fuel and biomass combustion was classified as the main anthropogenic source of the metal, but the neighborhood of a cement factory may be taken under consideration. Our results showed that the use of integrated geostatistical models allows for better data visualization and interpretation.

Arsenic and lead contamination in soil and in feathers of three resident passerine species in a semi-arid mining region of the Mexican plateau.

The current study aimed at quantifying arsenic and lead in feathers from three passerine species that are residents from areas exposed to mining activities (Toxostoma curvirostre, Campylorhynchus brunneicapillus, and Melozone fusca). Lead and As contents in bird feathers and in superficial soil samples were measured with AAS. Levels of these metals were compared between sites exposed and unexposed to mining. Possible correlations of As and Pb between superficial soil and bird feathers were also investigated. Soil metal concentrations were significantly higher near mining sites, and metal concentrations in bird feathers showed a behavior similar to those recorded for soil samples. Individual birds from polluted sites had higher mean feather metal concentrations in comparison with non-polluted sites; no differences in metal concentrations were recorded among bird species. This work constitutes a basis for monitoring contaminants, and for future toxicological studies attempting to understand the impact that some mining activities may have on bird populations.

Phytostabilization of Heavy Metals and Fungal Community Response in Manganese Slag under the Mediation of Soil Amendments and Plants.

The addition of soil amendments and plants in heavy metal-contaminated soil can result in a significant impact on physicochemical properties, microbial communities and heavy metal distribution, but the specific mechanisms remain to be explored. In this study, Koelreuteria paniculata was used as a test plant, spent mushroom compost (SMC) and attapulgite (ATP) were used as amendments, and manganese slag was used as a substrate. CK (100% slag), M0 (90% slag + 5% SMC + 5% ATP) and M1 (90% slag + 5% SMC + 5% ATP, planting K. paniculata) groups were assessed in a pilot-scale experiment to explore their different impacts on phytoremediation. The results indicated that adding the amendments significantly improved the pH of the manganese slag, enhancing and maintaining its fertility and water retention. Adding the amendments and planting K. paniculata (M1) significantly reduced the bioavailability and migration of heavy metals (HMs). The loss of Mn, Pb and Zn via runoff decreased by 15.7%, 8.4% and 10.2%, respectively, compared to CK. K. paniculata recruited and enriched beneficial fungi, inhibited pathogenic fungi, and a more stable fungal community was built. This significantly improved the soil quality, promoted plant growth and mitigated heavy metal toxicity. In conclusion, this study demonstrated that the addition of SMC-ATP and planting K. paniculata showed a good phytostabilization effect in the manganese slag and further revealed the response process of the fungal community in phytoremediation.

[Characteristics of Cd Fluxe in Topsoil Around Typical Mining Area in Hezhou, Guangxi].

Guangxi is a typical geological high background area in southwest China, where carbonates, black rock series, basic-ultrabasic rock mass, and metal deposits (mineralized bodies) exhibit strong weathering into loam, resulting in higher cadmium (Cd) content in the soil than that in other areas of China. In order to investigate the degree of influence of mining activities on topsoil environmental quality in the area with high geological background, we chose a mining area and control area in Hezhou for this research and systematically carried out a comparative study on Cd transport routes and transport flux density in topsoil. The results showed that the average atmospheric dry and wet deposition flux densities of Cd in the soil of the mining area and control area were 1.87 g·(hm2·a)-1 and 1.52 g·(hm2·a)-1, accounting for 61.5% and 60.3% of the total input flux density, respectively. The flux density of Cd in the soil by fertilization and irrigation was lower. Surface water infiltration was the main avenue of soil Cd output in both the mining area and control area, accounting for 75.4% and 86.6% of the total output flux density, respectively. The harvest output flux density in the mining area was higher than that in the control area, and the Cd content of rice planted in the mining area was higher than the standard, whereas that of maize was safe. On the whole, the net transport flux densities of soil Cd in the mining area and control area were -3.05 g·(hm2·a)-1 and -4.05 g·(hm2·a)-1, both of which showed Cd leaching in the soil. However, the points of high atmospheric deposition flux density and exceeding Cd content in rice were mainly distributed around the mining area, which may have posed a potential threat to the health of local residents. Therefore, it is suggested to control the soil Cd pollution through monitoring and planting structure adjustment.

Geochemical Distribution and Environmental Risks of Radionuclides in Soils and Sediments Runoff of a Uranium Mining Area in South China.

Uranium mining activities have contributed to the distribution and uptake of radionuclides, which have increased the active concentrations of natural radionuclides in environmental media, causing elevated human health risks. The present study aims to assess the spatial distribution characteristics of natural radionuclides in the surface soils and river sediments of the typical granite uranium mining area in South China, as well as investigate the geochemical features of natural radionuclides in the soil and sediments to understand their migration processes. The activity concentrations for 238U, 226Ra, 232Th, and 40K ranged from 17-3925 Bq/kg, 50-1180 Bq/kg, 29-459 Bq/kg, and 240-1890 Bq/kg, respectively. The open-pit mining areas and tailings pond locations exhibited the highest concentrations of activity for all these radionuclides. This distribution points to an elevated potential health risk due to radiological exposure in these specific areas. Additionally, the values of radium equivalent activity (Raeq) and annual gonadal dose equivalent (AGDE) in those areas were higher than the limits recommended by ICRP (2021). 238U and 226Ra have a significant correlation (0.724), and the cluster analysis was showing a statistically meaningful cluster below 5 indicated that they have similar behavior during parent rock weathering and watershed erosion, and the distribution of 232Th and 40K were influenced by the addition of rock types. The activity ratios of 226Ra/238U, 226Ra/232Th, 238U/40K, and 226Ra/40K variation indicated that 40K more mobile than 226Ra and 238U, U(VI) was reduced to U(IV) by organic matter in the downstream area and re-entered into the sediment during the sediment surface runoff in the small watershed of the uranium ore open-pit mining area. Therefore, it is necessary to further seal up and repair the tailings landfill area.

Extraction of vegetation disturbance range using aboveground biomass estimated from Sentinel-2 imagery in coal mining areas with high groundwater table.

Coal mining in regions characterized by high groundwater table markedly predisposes to surface subsidence and water accumulation, thereby engendering substantial harm to surface vegetation, soil, and hydrological resources. Developing effective methods to extract surface disturbance information aids in quantitatively assessing the comprehensive impacts of coal mining on land, ecology, and society. Due to the shortcomings of traditional indicators in reflecting mining disturbance, vegetation aboveground biomass (AGB) is introduced as the primary indicator for extracting the mining disturbance range. Taking the Huaibei Coal Base as an example, Sentinel-2 MSI imagery is firstly used to calculate spectral factors and vegetation indices. Multiple machine learning algorithms are coupled to perform remote sensing estimation and spatial inversion of vegetation AGB based on measured samples of vegetation AGB. Secondly, an Orientation Distance-AGB (OD-AGB) curve is constructed outward from the center of subsidence water areas (SWA), with the Boltzmann function used for curve fitting. According to the location of the inflection point of the curve, the boundary points of vegetation disturbance are identified, and then the disturbance range is divided. The results show that (1) the TV-SVM model, utilizing total variables and support vector machine, achieves the highest estimation accuracy, with σMAE and σRMSE values of 208.47 g/m2 and 290.19 g/m2, respectively, for the validation set. (2) Thirty-six effective disturbance areas, totaling 29.89 km2, are identified; the Boltzmann function provides a good fit for the OD-AGB curve, with an R2 exceeding 0.8 for typical disturbance areas. (3) Analysis of general statistical laws indicates that disturbance distance conforms to the general characteristics of normal distribution, exhibiting boundedness and directional heterogeneity. The research is expected to provide scientific guidance for hierarchical zoning management, land reclamation, and ecological restoration in coal mining areas with high groundwater table.