Succession of Microbial Communities in Waste Soils of an Iron Mine in Eastern China

The reclamation of mine dump is largely centered on the role played by microorganisms. However, the succession of microbial community structure and function in ecological restoration of the mine soils is still poorly understood. In this study, soil samples with different stacking time were collected from the dump of an iron mine in China and the physicochemical characteristics and microbial communities of these samples were comparatively investigated. The results showed that the fresh bare samples had the lowest pH, highest ion concentration, and were the most deficient in nutrients while the acidity and ion concentration of old bare samples decreased significantly, and the nutritional conditions improved remarkably. Vegetated samples had the weakest acidity, lowest ion concentration, and the highest nutrient concentration. In the fresh mine soils, the iron/sulfur-oxidizers such as Acidiferrobacter and Sulfobacillus were dominant, resulting in the strongest acidity. Bacteria from genera Acidibacter, Metallibacterium, and phyla Cyanobacteria, WPS-2 were abundant in the old bare samples, which contributed to the pH increase and TOC accumulation respectively. Acidobacteriota predominated in the vegetated samples and promoted nutrient enrichment and plant growth significantly. The microbial diversity and evenness of the three types of soils increased gradually, with more complex microbial networks, suggesting that the microbial community became more mature with time and microorganisms co-evolved with the mine soils.

STUDY OF FLY ASH FROM POWER GENERATING ENTERPRISES TO USE IT AS AN ALTERNATIVE TO LIME MINERAL FILLER FOR THE PRODUCTION OF ASPHALT MIXTURES

Introduction. Asphalt mixtures are one of the most widely used materials in the construction of roads. For the production of these mixtures, mainly conditioned mineral materials are used — coarse aggregate, fine aggregate and filler, and bitumen is used as a binder. Problem statement. In Ukraine, the filler is mainly used material obtained by grinding the carbonate rocks, which is established in DSTU B V.2.7-119 and DSTU B V.2.7-121. At the same time, as a result of coal combustion, millions of tons of dusty waste are generated at power generating plants of Ukraine - fly ashes and ashes from the hydraulic mine dump. These materials are close by grading to the requirements for the filler in accordance with DSTU B V.2.7-121 and probably can be used for the production of asphalt mixtures. Purpose. Determination of the possibility of using the fly ashes for the production of asphalt mixtures. Materials and methods. Type B asphalt concrete and mineral fillers of different origins were used during the research. Results. Test results showed that the studied fly ashes can be used for the production of asphalt mixtures, because the complete replacement of limestone filler with fly ashes from the thermal power plants does not lead to the deterioration of asphalt mixtures properties.

Extremophiles in Soil Communities of Former Copper Mining Sites of the East Harz Region (Germany) Reflected by Re-Analyzed 16S rRNA Data

The east and southeast rim of Harz mountains (Germany) are marked by a high density of former copper mining places dating back from the late 20th century to the middle age. A set of 18 soil samples from pre- and early industrial mining places and one sample from an industrial mine dump have been selected for investigation by 16S rRNA and compared with six samples from non-mining areas. Although most of the soil samples from the old mines show pH values around 7, RNA profiling reflects many operational taxonomical units (OTUs) belonging to acidophilic genera. For some of these OTUs, similarities were found with their abundances in the comparative samples, while others show significant differences. In addition to pH-dependent bacteria, thermophilic, psychrophilic, and halophilic types were observed. Among these OTUs, several DNA sequences are related to bacteria which are reported to show the ability to metabolize special substrates. Some OTUs absent in comparative samples from limestone substrates, among them Thaumarchaeota were present in the soil group from ancient mines with pH > 7. In contrast, acidophilic types have been found in a sample from a copper slag deposit, e.g., the polymer degrading bacterium Granulicella and Acidicaldus, which is thermophilic, too. Soil samples of the group of pre-industrial mines supplied some less abundant, interesting OTUs as the polymer-degrading Povalibacter and the halophilic Lewinella and Halobacteriovorax. A particularly high number of bacteria (OTUs) which had not been detected in other samples were found at an industrial copper mine dump, among them many halophilic and psychrophilic types. In summary, the results show that soil samples from the ancient copper mining places contain soil bacterial communities that could be a promising source in the search for microorganisms with valuable metabolic capabilities.

A UAV- and field-based investigation of the land degradation and soil erosion at opencast coal mine dumps after 5 years’ evolution of natural processes

Open-pit coal mining has a large impact on land surface, both at the mining pits themselves and at waste sites. After artificial management is stopped, a reclaimed opencast coal mine dump is affected by wind and water erosion from natural processes, resulting in land degradation and even safety incidents. In this paper, the soil erosion and land degradation after 5 years of such natural processes, at the Xilinhot open pit coal mine dump in Inner Mongolia, were investigated. A multi-source data acquisition method was applied: the vegetation coverage index was extracted from GF-1 satellite imagery, high-precision terrain characteristics and the location and degree of soil erosion were obtained using an Unmanned Aerial Vehicle (UAV), and the physical properties of the topsoil were obtained by field sampling. On this basis, the degree and spatial distribution of erosion cracks were identified, and the causes of soil erosion and land degradation were analyzed using a geographical detector. The results show that: 1) The multi-source data acquisition method can provide effective basic data for the quantitative evaluation of the ecological environment at dumps; 2) slope aspect and vegetation fractional coverage are the main factors affecting the degree of degradation and soil erosion. Based on this analysis, several countermeasures are proposed to mitigate land degradation: 1) The windward slope be designed to imitate the natural landform; 2) engineering measures should be applied at the slope to restrain soil erosion; 3) pioneer plants should be widely planted on the platform at the early stage of reclamation.