The coal industry plays an important role in the economic and energy sectors. Coal is an important energy source. The coal industry of Ukraine occupies one of the leading positions in the economic and energy sector. 32,7% of electricity in Ukraine is produced by coal (Pic.1) [1].
Picture 1. Production of electricity in Ukraine
However, the coal industry has a negative impact on the environment. The coal industry is classified as one of the industries that has a negative impact on the environment, which is manifested in high levels of noise and vibrations; atmospheric pollution by solid and gaseous harmful substances emissions; the negative impact on the water basin due to the discharge of mine water contaminated with mineral and mechanical impurities; land disturbance by mining operations and dumps. The main consequences of underground coal mining are coal dumps and land subsidence. Accordingly, it changes the biogeocenosis of this region. The industrial sector of Ukraine also has a negative impact on environmental biodiversity. Approximately 8.3% of vascular plants, 31.1% of mammals, 19.7% of birds, 38% of reptiles, and 26.3% of amphibians are threatened with extinction. Extraction of minerals, industrial facilities, generation and accumulation of waste - all this is directly or indirectly related to biogeocenosis [2].
Research has shown that the coal dumps of Western Donbass contain PTE’s ( Potential toxic element’s). These are elements such as: Co; As; Cu; Pb; Mn and Zn that exceed the TLV (Threshold limit value) by 59; 38; 47; 11.5; 2.5 and 25 times, respectively [3]. It was investigated that the pH of the soil from the reclamation site is 7.68, the specific electrical conductivity value is 1200 µS/cm. The results of the spectrophotometric analysis of the provision of the substrate with nutrients for plants indicate an insufficient amount of nitrate (from 0.007 mg/kg) and ammonium form of nitrogen (0.11 mg/kg), as well as phosphates (0.016 mg/kg) [3].
One of the methods for solving this problem is remediation of coal dumps. One of them is bioremediation. Bioremediation or phytoremediation can be an alternative to this. Phytoremediation is a method of cleaning water, soil and air using green plants. There are various types of phytoremediation such as: phytostabilization, phytoextraction, rhizofiltration, phytodegradation, phytovolotization, phytoevaporation and others [4]. One of the ways to improve the phytoremediation process is the use of microorganisms. Microorganisms can stimulate the growth of plants and improve tolerance to PTE’s [5]. It was shown that rhizobacteria contribute to plant growth, protect against pathogens, and increase resistance to heavy metals. This all happens through the production of organic acids, siderophys, antibiotics and enzymes [6].
Microorganisms were analyzed according to these indicators to improve the phytoremediation process. Studies of bacteria such as Bacillus, Escherichia, and Mycobacterium have reported effective bioremoval of heavy metals [7].
One of the types of influence of microorganisms is the oxidation-reduction reaction. It is known that Arthrobacter, Bacillus, Cymodocea, Phanerochaete, Pseudomonas, Rhizopus and Saccharomyces make heavy metals less toxic due to enzymatic transformations [8]. In order to dissolve metal compounds, some microbes make amino acids and organic acids. These processes change the chemical composition of metals, and accordingly, their toxicity is also reduced. It has been studied that Clostridium produces organic acids (butyric, acetic and lactic) to dissolve Cu, Zn, Cr, Fe and Mn oxides [9].
The functions of microorganisms can be enhanced when they react with the plant root system. For example, in the root system of Withania somnifera, remediation indicators increased after adding Staphylococcus cohnii [10]. Scirpus triquetra was planted for phytoremediation on the soils contaminated with Nickel. After adding HD-1 pyrene-decomposing bacteria, the rate of nickel decomposition in the substrate increased from 19.5% to 51.4% [11]. Also, an increase in the rate of decrease in the concentration of elements such as Cd and Cu was observed when Mycobacterium and Pseudomonas interact [12]. Species such as Bacillus and Pseudomonas stimulate plant growth, which in turn contributes to the improvement of the phytoremediation process as well. In addition to enzyme production, microorganisms also produce various metabolites to increase the bioavailability of undissolved salts [13].
Also, some microorganisms can increase the bioavailability of heavy metals. These microorganisms can secrete enzymes and chelate, which leads to the formation of a heavy metal-chelate complex, thus improving the uptake of this heavy metal by the plant [13].
Phytoremediation is a promising form of remediation of coal dumps. One of the main drawbacks of this process is the time. The application of microorganisms can speed up and improve this process. These microorganisms will also improve conditions for the growth of plants. The effectiveness of the use of microorganisms depends on the correct physico-chemical analysis of the substrate under study. Correct selection of microorganisms and plants will make it possible to improve the phytoremediation process. After all, some microorganisms can improve the growth of plants. Microorganisms such as Bacillus and Pseudomonas stimulate root growth. Other microorganisms such as: Gibberella, Aureobasidium, Saccharomyces and Phellinus release special enzymes to increase the absorption of toxic elements by plants. Other microorganisms such as: Bacillus, Escherichia, and Mycobacterium and Clostridium influence the bioavailability of toxic elements in the substrate. At the moment, the use of microorganisms for phytoremediation of coal dumps in Western Donbass has not been sufficiently studied, which reserves the right for further research in this topic. With the correct selection of plants and microorganisms, the process of phytoremediation can be accelerated.
References:
1. Gajko, G. I., & Bilec’kyj, V. S. (2013). Istorija girnyctva [History of mining]. Kyiv: DonDTU;
2. Vydobutok i zbagachennja vugillja [Coal mining and enrichment]. https://energo.dtek.com/business/coal_industry;
3. Krasovskyi S., Kovrov O., Klimkina I. (2021). Determination of physico-chemical characteristics of the coal dump “Heroiv Kosmosy”. [Ecological Sciences] № 6 (39). p. 137-140. https://doi.org/10.32846/2306-9716/2021.eco.6-39.23;
4. Zhengfu B, Hilary I, John D, Frank O, Sue S (2010). Environmental issues from coal mining and their solutions. [Mining Science and Technology]. №20 p.0215–0223;
5. Fasani, E., Manara, A., Martini, F., Furini, A., and DalCorso, G. (2018). The potential of genetic engineering of plants for the remediation of soils contaminated with heavy metals. [Plant, Cell and Environment]. №41. p.1201–1232. doi: 10.1111/pce.12963;
6. Ma, Y., Prasad, M., Rajkumar, M., and Freitas, H. (2011). Plant growth promoting rhizobacteria and endophytes accelerate phytoremediation of metalliferous soils. [Biotechnology] №29. p. 248–258. doi: 10.1016/j.biotechadv.2010.12.001;
7. Chen S, Duan G, Ding K, Huang F, Zhu Y (2018) DNA stable-isotope probing identifes uncultivated members of Pseudonocardia associated with biodegradation of pyrene in agricultural soil. [FEMS Microbiology Ecology] №94:026;
8. Gadd G.M. (2000) Bioremedial potential of microbial mechanisms of metal mobilization and immobilization. [Current Opinion in Biotechnology] №11p. 271–279;
9. Francis A.J., Dodge C.J. (1988) Anaerobic microbial dissolution of transition and heavy metal oxides. [Applied and Environmental Microbiology] №54 p.1009–1014;
10. Abhilash P.C., Srivastava S., Srivastava P., Singh B., Jafri A., Singh N. (2011) Infuence of rhizospheric microbial inoculation and tolerant plant species on the rhizoremediation of lindane. [Environmental and Experemintal Botany] №74 p.127–130;
11. Hu X, Zhang X, Liu X, Cao L, Chen J, Huo Z (2017) The contribution of pyrene degrading bacteria and chemical reagents to Scirpus triqueter phytoremediation of pyrene and Ni co-contaminated soil. [Water, Air and Soil Pollution] p. 228:295;
12. Brito E.M., De L.N., Caretta C.A., Goã I., Urriza M., Andrade L.H., Cuevas-Rodrã Guez G., Malm O., Torres J.P., Simon M., Guyoneaud R. (2015) Impact of hydrocarbons, PCBs and heavy metals on bacterial communities in Lerma River, Salamanca, Mexico: investigation of hydrocarbon degradation potential. [Science of the Total Environment] №521–522 p.1–10;
13. Clemens, S., Palmgren, M. G., and Krämer, U. (2002). A long way ahead: understanding and engineering plant metal accumulation. [Trends in Plants Science]. №7 p.309–315. doi: 10.1016/S1360-1385(02)02295-1.
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Наукові керівники:
Ковров Олександр Станіславович, д.т.н., професор кафедри екології та технологій захисту навколишнього середовища;
Клімкіна Ірина Іванівна, доцент кафедри екології та технологій захисту навколишнього середовища;
Хальмаєр Герман, д.б.н. професор кафедри хімії, Технічний Універиситет «Фрайберзька гірнича академія»
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