The impact of microbial community structure changes on the migration and release of typical heavy metal (loid)s during the revegetation process of mercury-thallium mining waste slag.

The effect of changes in microbial community structure on the migration and release of toxic heavy metal (loid)s is often ignored in ecological restoration. Here, we investigated a multi-metal (mercury and thallium, Tl) mine waste slag. With particular focus on its strong acidity, poor nutrition, and high toxicity pollution characteristics, we added fish manure and carbonate to the slag as environmental-friendly amendments. On this basis, ryegrass, which is suitable for the remediation of metal waste dumps, was then planted for ecological restoration. We finally explored the influence of changes in microbial community structure on the release of Tl and As in the waste slag during vegetation reconstruction. The results show that the combination of fish manure and carbonate temporarily halted the release of Tl, but subsequently promoted the release of Tl and arsenic (As), which was closely related to changes in the microbial community structure in the waste slag after fish manure and carbonate addition. The main reason for these patterns was that in the early stage of the experiment, Bacillaceae inhibited the release of Tl by secreting extracellular polymeric substances; with increasing time, Actinobacteriota became the dominant bacterium, which promoted the migration and release of Tl by mycelial disintegration of minerals. In addition, the exogenously added organic matter acted as an electron transport medium for reducing microorganisms and thus helped to reduce nitrate or As (Ⅴ) in the substrate, which reduced the redox potential of the waste slag and promoted As release. At the same time, the phylum Firmicutes, including specific dissimilatory As-reducing bacteria that are capable of converting As into a more soluble form, further promoted the release of As. Our findings provide a theoretical basis for guiding the ecological restoration of relevant heavy-metal (loid) mine waste dumps.

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 14 days, 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.

Screening of salt tolerance of maize (Zea mays L.) lines using membership function value and GGE biplot analysis.

Soil salinization is a widely recognized global environmental concern that has a significant impact on the sustainable development of agriculture at a global scale. Maize, a major crop that contributes to the global agricultural economy, is particularly vulnerable to the adverse effects of salt stress, which can hinder its growth and development from germination to the seedling stage. This study aimed to screen highly salt-tolerant maize varieties by using four NaCl concentrations of 0, 60, 120, and 180 mMol/L. Various agronomic traits and physiological and biochemical indices associated with salt tolerance were measured, and salt tolerance was evaluated using principal component analysis, membership function method, and GGE biplot analysis. A total of 41 local maize varieties were assessed based on their D values. The results show that stem thickness, germ length, radicle length, leaf area, germination rate, germination index, salt tolerance index, and seed vigor all decreased as salt concentration increased, while electrical conductivity and salt injury index increased with the concentration of saline solution. Under the stress of 120 mMol/L and 180 mMol/L NaCl, changes in antioxidant enzymes occurred, reflecting the physiological response mechanisms of maize under salt stress. Principal component analysis identified six major components including germination vigor, peroxidase (POD), plant height, embryo length, SPAD chlorophyll and proline (PRO) factors. After calculating the comprehensive index (D value) of each variety's performance in different environments using principal component analysis and the membership function method, a GGE biplot analysis was conducted to identify maize varieties with good salt tolerance stability: Qun Ce 888, You Qi 909, Ping An 1523, Xin Nong 008, Xinyu 66, and Hong Xin 990, as well as varieties with poor salt tolerance: Feng Tian 14, Xi Meng 668, Ji Xing 218, Gan Xin 2818, Hu Xin 712, and Heng Yu 369. Furthermore, it was determined that a 120 mMol/L NaCl concentration was suitable for screening maize varieties during germination and seedling stages. This study further confirmed the reliability of GGE biplot analysis in germplasm selection, expanded the genetic resources of salt-tolerant maize, and provided theoretical references and germplasm utilization for the introduction of maize in saline-alkali areas. These research findings contribute to a better understanding of maize salt tolerance and promote its cultivation in challenging environments.

Comprehensive Evaluation and Selection of 192 Maize Accessions from Different Sources.

In the period 2022-2023, an analysis of fourteen phenotypic traits was conducted across 192 maize accessions in the Aral region of Xinjiang. The Shannon-Wiener diversity index was employed to quantify the phenotypic diversity among the accessions. Subsequently, a comprehensive evaluation of the index was performed utilizing correlation analysis, principal component analysis (PCA) and cluster analysis. The results highlighted significant findings: (1) A pronounced diversity was evident across the 192 maize accessions, accompanied by complex interrelationships among the traits. (2) The 14 phenotypic traits were transformed into 3 independent indicators through principal component analysis: spike factor, leaf width factor, and number of spikes per plant. (3) The 192 materials were divided into three groups using cluster analysis. The phenotypes in Group III exhibited the best performance, followed by those in Group I, and finally Group II. The selection of the three groups can vary depending on the breeding objectives. This study analysed the diversity of phenotypic traits in maize germplasm resources. Maize germplasm was categorised based on similar phenotypes. These findings provide theoretical insights for the study of maize accessions under analogous climatic conditions in Alar City, which lay the groundwork for the efficient utilization of existing germplasm as well as the development and selection of new varieties.

Experimental study on new structure teeth in a high-temperature environment.

In high-temperature drilling, especially in high-temperature geothermal drilling, cone bits often experience common and severe tooth loss. This issue significantly reduces the cone bit's service life and has a detrimental impact on drilling efficiency. The quality of the fixed teeth plays a crucial role in the performance of the cone bit. In high-temperature environments, conventional methods fail to meet the requirements for securing the cone bit's teeth. Therefore, to address the tooth loss problem in high-temperature drilling, a new tapered tooth structure is proposed. Laboratory experiments were conducted to secure teeth with varying tapers at both normal and high temperatures. The results revealed that the maximum fastening force increased progressively with the degree of taper, reaching its peak at C50. Compared to conventional cylindrical teeth, the maximum fastening force increased by approximately 88.6%-271.1% at different temperatures. The tapered structure demonstrated superior tooth-fixing strength. The maximum fastening force is the smallest at 300 °C, approximately 23.7%-61.2% lower than at normal temperature. Under the same interference conditions, the maximum fastening force increased with greater taper. With interference values of 0.075, 0.095, and 0.115, the maximum fastening force increased by 48.9%-175.1%, 14%-141.6%, and 53%-271.1%, respectively, when compared to cylindrical teeth with C300, C200, C100, and C50 tapers. The tapered structure exhibited superior tooth-fixing strength and significantly enhanced tooth retention strength at high temperatures.

Study on bioleaching of heavy metals and resource potential from tannery yard sludge.

Tannery sludge that has accumulated in the natural environment of a tannery industrial zone for a long time contains large amounts of toxic heavy metal elements such as Cr, which has a serious impact on the surrounding environment. This study used indigenous acidophilic sulfur-oxidizing bacteria from local tannery wastewater treatment plants to examine the effects of bioleaching on the removal of heavy metals in local tannery sludge accumulated in the natural environment. The effect of pre-oxygenation on bioleaching was investigated, and trends of sludge dewaterability during bioleaching and changes in the total amount of heavy metals, total nitrogen (TN), and total phosphorus (TP) during bioleaching were determined. Changes in the contents of different bound forms of heavy metals in tannery yard sludge during the bioleaching process were revealed. The experimental results showed that pre-oxygenation treatment of tannery yard sludge can shorten the bioleaching period (by at least 4 days) and improve the removal efficiency of all heavy metals. To ensure sludge dewaterability, the pH of the leaching system at the end of the bioleaching must not be lower than 1.67. The main components of heavy metals were stable in the tannery yard sludge, which critically affected the final removal efficiency of all heavy metals. The dissolution process of heavy metals showed that the morphology of heavy metals changed from stable to unstable forms in the bioleaching process, further dissolving into the liquid phase to be removed. In this experiment, the removal efficiency of all heavy metals in the tannery yard sludge was higher than 88.49%, and these heavy metals had good stability in morphology (the stable forms accounted for more than 87% of the total). In addition, the TN content in the remaining sludge was 27.9 g/kg, which is much higher than fertilizer TN requirements, indicating a high potential for resource utilization. Therefore, the method of bioleaching to remove heavy metals in tannery yard sludge for reuse is worthy of in-depth study and promotion.