Effect of Bactericides on Control of Acidification Pollution and Spontaneous Combustion of Coal Gangue Dumps in China and Its Mechanism

The Effects of Low Concentrations and Long-Term Contamination by Sodium Dodecyl Sulfate on the Structure and Function of Bacterial Communities in the Lake-Terrestrial Ecotone

Due to the growing focus on daily hygiene practices, sodium dodecyl sulfate (SDS), a widely used surfactant, is increasingly found in domestic sewage and rainfall runoff. Upon entering the lake-terrestrial ecotone, SDS affects the composition, abundance, and functional capacity of soil bacterial communities due to its bacteriostatic properties. To investigate the effects of long-term discharge of sewage containing low concentrations of SDS on microorganisms in the lake-terrestrial ecotone, alterations in bacterial community structure, functional genes, and biomass were examined using a simulated continuous pollutant input. The results indicated the following: (1) The degradation rate of sodium dodecyl sulfate (SDS) by soil microorganisms in the lake-terrestrial ecotone under long-term and low concentrations of SDS stress ranged from 11 to 16 mg/kg·d. (2) The effects of low concentrations and long-term SDS stress on bacterial community structure and gene function in the lake-terrestrial ecotone differed significantly from those of short-term pollution. The damage to microbial-promoted material cycling in the lake-terrestrial ecotone was more severe; however, the proliferation of pathogenic bacteria remained continuously suppressed. (3) Soil bacteria in the lake-terrestrial ecotone responded to the stress of long-term and low concentrations of SDS primarily by enhancing chemotaxis and tolerance.

A review of passive acid mine drainage treatment by PRB and LPB: From design, testing, to construction

An extensive volume of acid mine drainage (AMD) generated throughout the mining process has been widely regarded as one of the most catastrophic environmental problems. Surface water and groundwater impacted by pollution exhibit extreme low pH values and elevated sulfate and metal/metalloid concentrations, posing a serious threat to the production efficiency of enterprises, domestic water safety, and the ecological health of the basin. Over the recent years, a plethora of techniques has been developed to address the issue of AMD, encompassing nanofiltration membranes, lime neutralization, and carrier-microencapsulation. Nonetheless, these approaches often come with substantial financial implications and exhibit restricted long-term sustainability. Among the array of choices, the permeable reactive barrier (PRB) system emerges as a noteworthy passive remediation method for AMD. Distinguished by its modest construction expenses and enduring stability, this approach proves particularly well-suited for addressing the environmental challenges posed by abandoned mines. This study undertook a comprehensive evaluation of the PRB systems utilized in the remediation of AMD. Furthermore, it introduced the concept of low permeability barrier, derived from the realm of site-contaminated groundwater management. The strategies pertaining to the selection of materials, the physicochemical aspects influencing long-term efficacy, the intricacies of design and construction, as well as the challenges and prospects inherent in barrier technology, are elaborated upon in this discourse.

The role of afforestation with diverse woody species in enhancing and restructuring the soil microenvironment in polymetallic coal gangue dumps

To elucidate the effects of long-term (20 years) afforestation with different woody plant species on the soil microenvironment in coal gangue polymetallic contaminated areas. This study analyzed the soil physicochemical properties, soil enzyme activities, soil ionophore, bacterial community structure, soil metabolite, and their interaction relationships at different vertical depths. Urease, sucrase, and acid phosphatase activities in the shallow soil layers increased by 4.70-7.45, 3.83-7.64, and 3.27-4.85 times, respectively, after the restoration by the four arboreal plant species compared to the plant-free control soil. Additionally, it reduced the content of available elements in the soil and alleviated the toxicity stress for Cd, Ni, Co, Cr, As, Fe, Cu, U, and Pb. After the long-term restoration of arboreal plants, the richness and Shannon indices of soil bacteria significantly increased by 4.77-23.81% and 2.93-7.93%, respectively, broadening the bacterial ecological niche. The bacterial community structure shaped by different arboreal plants exhibited high similarity, but the community similarity decreased with increasing vertical depth. Soils Zn, U, Sr, S, P, Mg, K, Fe, Cu, Ca, Ba, and pH were identified as important influencing factors for the community structure of Sphingomonas, Pseudarthrobacter, Nocardioides, and Thiobacillus. The metabolites such as sucrose, raffinose, L-valine, D-fructose 2, 6-bisphosphate, and oxoglutaric acid were found to have the greatest effect on the bacterial community in the rhizosphere soils for arboreal plants. The results of the study demonstrated that long-term planting for woody plants in gangue dumps could regulate microbial abundance and symbiotic patterns through the accumulation of rhizosphere metabolites in the soil, increase soil enzyme activity, reduce heavy metal levels, and improve the soil environment in coal gangue dumps.

Examining the effect of spontaneous combustion on vegetation restoration at coal waste dumps after reclamation: Taking Medicago sativa L. (alfalfa) as an indicator

The Spontaneous combustion problem poses a significant threat to the coal waste dumps after reclamation. Spontaneous combustion alters the soil environment and further affects vegetation growth. Therefore, it is essential to understand the response of vegetation and soil to spontaneous combustion for ensuring vegetation restoration. Here, taking the reclaimed plant type, Medicago sativa L. (alfalfa), as an indicator, this study carried out a field survey in a typical spontaneous combustion area (study area) of a coal waste dump after reclamation. A total of 41 soil and 70 vegetation sampling points were investigated in the field survey, including soil environmental factors (soil temperature, ST; soil water content, SWC; soil organic carbon, SOC; total nitrogen, TN; available phosphorus, AP; available potassium, AK; bulk density, BD; pH) and alfalfa growth indicator (above-ground biomass, AGB). The spatial variation of alfalfa AGB reached 69.9 %, and all soil environmental factors showed moderate variation (12.28-35.03 %) except for BD and pH. ST was found to have a strong explanatory ability on the variation of AGB in the entire study area (q = 0.62, p < 0.01), but the ability weakened with the improvement of the health grades of alfalfa (Grades A, B, C, and D). From Grade D to Grade A, the q-value gradually reduced from 0.71 (p < 0.01) to 0.05 (no significance). The interaction effects of soil environmental factors showed mostly bilinear and non-linear enhancement. In regions with severe vegetation degradation (Grade C and Grade D of alfalfa), the interaction of ST with BD, AP, AK, and TN played a dominant role in the spatial variation of alfalfa AGB (44.8-86.15 %). However, in the regions of Grade A and Grade B, the spatial variation of alfalfa AGB was mainly affected by the interaction effects of AK, TN, AP, and SOC (60.13-84.77 %). As a simple analysis method, Geodetector can help researchers to better understand the complex response mechanism of vegetation-soil under spontaneous combustion of coal waste dump. This study provides a theoretical reference for vegetation restoration of coal waste dumps.

16S rDNA Sequencing-Based Insights into the Bacterial Community Structure and Function in Co-Existing Soil and Coal Gangue

Coal gangue is a solid waste emitted during coal production. Coal gangue is deployed adjacent to mining land and has characteristics similar to those of the soils of these areas. Coal gangue-soil ecosystems provide habitats for a rich and active bacterial community. However, co-existence networks and the functionality of soil and coal gangue bacterial communities have not been studied. Here, we performed Illumina MiSeq high-throughput sequencing, symbiotic network and statistical analyses, and microbial phenotype prediction to study the microbial community in coal gangue and soil samples from Shanxi Province, China. In general, the structural difference between the bacterial communities in coal gangue and soil was large, indicating that interactions between soil and coal gangue are limited but not absent. The bacterial community exhibited a significant symbiosis network in soil and coal gangue. The co-occurrence network was primarily formed by Proteobacteria, Firmicutes, and Actinobacteria. In addition, BugBase microbiome phenotype predictions and PICRUSt bacterial functional potential predictions showed that transcription regulators represented the highest functional category of symbiotic bacteria in soil and coal gangue. Proteobacteria played an important role in various processes such as mobile element pathogenicity, oxidative stress tolerance, and biofilm formation. In general, this work provides a theoretical basis and data support for the in situ remediation of acidified coal gangue hills based on microbiological methods.

Mechanism of 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) in controlling microbial problems in aircraft fuel systems

This research investigated the potential use of 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) as a biocide in aircraft fuel systems, which is rarely studied due to the unique properties of such systems. The study assessed the effectiveness of CMIT against three microbial isolates using minimum inhibitory concentrations and bacteriostatic tests, and showed that CMIT had good activity against them. Electrochemical studies were conducted to determine the impact of CMIT on the 7B04 aluminum alloy, which demonstrated that CMIT acted as a cathodic inhibitor and exhibited certain levels of short-term and long-term corrosion inhibition effects at concentrations of 100 mg L^-1 and 60 mg L^-1, respectively. Additionally, the research provided insights into the mechanisms governing microbial problems by studying the reaction of CMIT with glutathione and sulfate. Overall, the study suggested that CMIT may be a useful biocide in aircraft fuel systems and provided important information on its efficacy and mechanism of action.

Addition of carbon sources and nutrient salts can inhibit gangue acidification by changing microbial community structure

Acidic pollution from gangue oxidation has become a primary environmental problem in coal mining areas in China. The use of microorganisms to remediate acidic pollution in coal gangue piles has been indicated to be effective, but environmental differences and carbon sources in different mining areas have become important factors restricting microbial activity. Instead of the addition of new functional bacteria to gangue piles, carbon sources and nutrient salts were added to recently discharged gangue to enhance the activity of beneficial bacteria in the indigenous microbial community. The changes in pH and electrical conductivity (EC) of the gangue leachate as well as the composition and abundance of the functional microbial community on the surface of the gangue were analyzed by leaching simulation experiments and 16S rRNA sequencing. The results showed that the addition of a carbon source maintained the pH of the gangue leachate at 6.31~6.65 in 14 d, which was significantly higher than that of the control group, but the pH of the leachate decreased significantly after the addition of the carbon source was stopped. The most effective treatment is adding a low concentration of nutrient salt (20% concentration) and sodium lactate (0.02 g/L) to the gangue first, and then adding sodium lactate (0.1 mg/L) every 7 days. The addition of carbon sources and nutrient salts changed the microbial community composition on the surface of the gangue, and the species diversity index decreased. The dominant genera in the experimental group were Listeria, Arthrobacter, and Enterococcus. The functional gene types in the experimental and control groups were almost the same, but their relative abundance changed. The abundance of functional genes related to the sulfur cycle increased substantially in the experimental group, and the abundance of genes involved in the nitrogen and carbon cycles also increased, albeit to different degrees.