Evaluation of metal pollution characteristics using water and moss in the Luanchuan molybdenum mining area, China.

Luanchuan is rich in molybdenum resources, and mining activities are frequent, but over-mining can cause serious metal pollution to the local environment. To explore the degree of metal pollution caused by mining activities, the content characteristics and spatial distribution of metals in mining areas were studied by measuring the concentrations of Fe, Mn, Zn, Ba, Mo, Cu, Cr, Co, V, and W in surface water and mosses of mining areas. In addition, the metal pollution index (HPI), contamination factor (CF), and pollution load index (PLI) were used to evaluate metal pollution, and factor analysis was used to analyze the sources of metals. The results of the analysis of surface water at the mine site indicate the most abundant element in surface water, with a maximum concentration of 3713.8 µg/L, and its content far exceeds the water quality standard of Class III of the Environmental Quality Standard for Surface Water. The results of the HPI analysis showed that nearly 90% of the surface water was moderately contaminated (HPI ≥ 15). The results of the analysis of atmospheric deposition at the mine site confirm that the metal elements with a high threat to the atmospheric environment are Mo and W. The results of PLI indicate that the level of atmospheric deposition pollution in the study area is severe (PLI > 4). Factor analysis indicated that rock weathering and mining activities were the main sources of metals. This study provides a theoretical basis for the investigation and control of metal pollution in similar metal mining areas.

Deciphering the impacts of chromium contamination on soil bacterial communities: A comparative analysis across various soil types.

Addressing the widespread concern of chromium (Cr) pollution, this study investigated its impacts on bacterial communities across eight soil types, alongside the potential Cr transformation-related genes. Utilizing real-time PCR, 16S rRNA gene sequencing and gene prediction, we revealed shifts in bacterial community structure and function at three Cr exposure levels. Our results showed that the bacterial abundance in all eight soil types was influenced by Cr to varying extents, with yellow‒brown soil being the most sensitive. The bacterial community composition of different soil types exhibited diverse responses to Cr, with only the relative abundance of Proteobacteria decreasing with increasing Cr concentration across all soil types. Beta diversity analysis revealed that while Cr concentration impacted the assembly process of bacterial communities to a certain extent, the influence on the compositional structure of bacterial communities was primarily driven by soil type rather than Cr concentration. The study also identified biomarkers for each soil type under three Cr levels, offering a basis for monitoring changes in Cr pollution. By predicting crucial functional genes related to Cr transformation, it was observed that the relative abundance of chrA (chromate transporter) in yellow‒brown soil significantly exceeded that in all other soil types, suggesting its potential for Cr adaptation. The study also revealed correlations among soil physicochemical properties, Cr concentration, and these functional genes, providing a foundation for future research aimed at more precise functional analysis and the development of effective soil remediation strategies.

Physicochemical properties of environmental media can affect the adsorption of arsenic (As) by microplastics.

Microplastics are emerging pollutants that can adsorb heavy metals and threaten human health through food chain. Recently, there has been increasing interest in understanding the adsorption behavior of heavy metals by microplastics in farmland soil. In particular, arsenic (As), as a carcinogen, has the potential to be adsorbed by soil microplastics. However, the mechanisms and controlling factors of As adsorption by microplastics in farmland soil under natural conditions are still unknown. Here, microplastics and As were respectively added to farmland soils with different physicochemical properties from twelve provinces of China for adsorption experiment. We performed surface analysis of microplastics, quantified As accumulation through quasi-first-order kinetic equation and developed regression models to screen the factors controlling As adsorption. The results showed that the adsorption of As by soil microplastics was a chemical process accompanied by the loss of electrons from oxygen-containing functional groups. Soil cation exchange capacity (CEC) was the main factor controlling the adsorption rate, while soil organic matter (SOM), total nitrogen (TN) and CEC mainly influenced the equilibrium adsorption capacity. This is the first report on microplastic-As adsorption in natural soil, which allows deeper insights into risk assessment, prediction and control of microplastic-As pollution in agricultural soil.

Response of soil fungal community to chromium contamination in agricultural soils with different physicochemical properties.

Chromium (Cr) contamination has been of great concern in agricultural soil health due to its persistence, toxicity and bioaccumulation. Fungi, as an essential regulator of soil remediation and biochemical processes, had an unclear response to Cr contamination. In this study, the composition, diversity and interaction mechanisms of fungal communities in agricultural soils from ten different provinces of China were investigated in order to elucidate the fungal community response to varying soil properties and Cr concentrations. The results showed that high concentrations of Cr led to substantial alterations in the fungal community composition. The complex soil properties had a far greater impact on the fungal community structure than the single factor of Cr concentration, with soil available phosphorus (AP) and pH being most influential. Function predictions based on FUNGuild indicated that high concentrations of Cr have a significant impact on certain functional groups of fungi, including mycorrhizal fungi and plant saprotroph. The fungal community tended to resist Cr stress by enhancing interactions and clustering among network modules, while generating new keystone taxa. This study allowed insights into the response of soil fungal community to Cr contamination in different agricultural soils from different provinces and provided a theoretical basis for soil Cr ecological risk assessment and the development of bioremediation techniques for Cr-contaminated soils.

Community response of soil microorganisms to combined contamination of polycyclic aromatic hydrocarbons and potentially toxic elements in a typical coking plant.

Both polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs) of coking industries impose negative effects on the stability of soil ecosystem. Soil microbes are regarded as an essential moderator of biochemical processes and soil remediation, while their responses to PAHs-PTEs combined contamination are largely unknown. In the present study, soil microbial diversity and community composition in the typical coking plant under the chronic co-exposure of PAHs and PTEs were investigated and microbial interaction networks were built to reveal microbial co-occurrence patterns. The results indicated that the concentrations of PAHs in the soil inside the coking plant were significantly higher than those outside the plant. The mean concentration of ∑16PAHs was 2894.4 ng·g-1, which is 5.58 times higher than that outside the plant. The average Hg concentration inside the coking plant was 22 times higher than the background value of Hebei province. The soil fungal community inside the coking plant showed lower richness compared with that of outside community, and there are significant difference in the bacterial and fungal community composition between inside and outside of coking plant (p < 0.01). Predicted contribution of different environmental factors to each dominant species based on random forest identified 20 and 25 biomarkers in bacteria and fungi, respectively, that were highly sensitive to coking plant soil in operation, such as Betaproteobacteria，Sordariomycetes and Dothideomycetes. Bacterial and fungal communities were shaped by the soil chemical properties (pH), PTEs (Hg), and PAHs together in the coking plant soils. Furthermore, the bacterial and fungal interaction patterns were investigated separately or jointly by intradomain and interdomain networks. Competition is the main strategy based on the co-exclusion pattern in fungal community, and the competitive relationship inside the coking plant is more complex than that outside the plant. In contrast, cooperation is the dominant strategy in bacterial networks based on the co-occurrence pattern. The present study provided insights into microbial response strategies and the interactions between bacteria and fungi under long-term combined contamination.

Do the Reclaimed Fungal Communities Succeed Toward the Original Structure in Eco-Fragile Regions of Coal Mining Disturbances? A Case Study in North China Loess-Aeolian Sand Area.

Mining activity has caused serious environmental damage, particularly for soil ecosystems. How the soil fungal community evolves in mine reclamation and what are the succession patterns of molecular ecological networks still needs to be studied in depth. We used high-throughput sequencing to explore the changes in soil fungal communities, molecular ecological networks, and interactions with soil environmental factors in five different ages (the including control group) during 14 years of reclamation in eco-fragile mines. The results showed that the abundance and diversity of soil fungi after 14 years of reclamation were close to, but still lower than, those in the undisturbed control area, but the dominant phylum was Ascomycota. Soil nitrate-N, C/N ratio, pH, and water content significantly affected the fungal community with increasing reclamation ages. Moreover, we found that Mortierellomycota, despite its high relative abundance, had little significant connectivity with other species in the molecular ecological network. Fungal molecular ecological networks evolve with increasing ages of reclamation, with larger modules, more positive connections, and tighter networks, forming large modules of more than 60 nodes by age 9. The large modules were composed mainly of Ascomycota and Basidiomycota, which can form mycorrhiza with plant roots, and are not only capable of degrading pollution but are also "encouraged" by most (more than 64%) physicochemical factors in the soil environment. The results can provide a basis for scientific mine ecological restoration, especially for eco-fragile regions.

Feasibility Study on the Application of Microbial Agent Modified Water-Jet Loom Sludge for the Restoration of Degraded Soil in Mining Areas.

Open-pit mining causes soil damage and affects the health of the ecosystem. In the arid grassland mining areas, the soil is severely sanded, water-starved, and saline, thus making it difficult for plants and microorganisms to survive. Water-jet loom sludge can be used to improve the quality as it contains a lot of clay and is rich in organic matter, which provides a material basis for microorganism activity. To explore the effects of microbial agent-modified water-jet loom sludge on the restoration of degraded soil in grassland mining areas, four pot trials were set up, i.e., for untreated soil, the application of a microbial agent alone, the application of water-jet loom sludge alone, and the combined application of water-jet loom sludge and the microbial agent. The results show that (1) microbial agent-modified sludge can improve soil water-holding capacity and aggregate stability; (2) the nutrient content of the restored soil fraction increased significantly, and the pH of the original saline soil decreased from 9.06 to 7.84; (3) this method significantly increased plant biomass and microbial biomass carbon and enhanced the abundance and diversity of fungi and bacteria. The three treatments had different results in different soil properties, and the effect of the combined water-jet loom sludge and microbial agent treatment on soil remediation was significantly better than the individual application of either.