121 / 2021-09-30 21:09:02

Land reclamation of coal mine affected areas in highly acidic waste heaps

coal combustion by-products,industrial waste,phitotoxicity test,soil substitutes

The basic purpose of this paper is to outline a novel approach in the use of wastes generated in coal mines and coal-fired power plants. The research was performed under the European research project RECOVERY focused on land rehabilitation and ecological restoration of coal mining-affected areas, aiming at accelerating the reclamation of degraded and transformed ecosystems to a eco-friendly status.

The reclamation of coal waste heaps requires the use of complex techniques capable of improving surface and groundwater quality. The problem of pollution in areas affected by coal mines is the chemical aggressiveness of acidic runoff water [1] and heavy metals [2,3]. Mine waste materials in waste heaps also contain a very low concentration of macronutrients, i.e., nitrogen (N), phosphorus (P) and potassium (K), calcium (Ca), magnesium (Mg), sodium (Na) and organic matter necessary for spontaneous vegetation succession [4]. The objective of this research was to use by-products generated in coal mining and coal-fired power plant processes as components of artificial soil substitutes. The study was conducted in laboratory conditions and in the experimental field located at the Janina waste heap in Libiąż (Fig. 1) area of biodiversity loss and high acidic character [5]. Various industrial waste mixtures, including fly ash and energy sludge from coal mine combustion, fly ash from biomass combustion, decarbonization lime, aggregates and sealing material from waste treatment, were tested as soil substitute components. In addition, sewage sludge and spent mushroom compost were incorporated in the preparation of soil substitutes as substrates enriched with organic matter and valuable nutrients (N, P, K).

The soil blends were differentiated from each other by the type of residues and their percentage. The study includes four types of soil substitutes created for different plant communities, such as dry and moderate fertility, mesic and low fertility, mesic and moderate fertility, wet and low fertility.

Phytotoxicity test using white mustard (Sinapis alba L.) seeds as a typical test plant [6] under laboratory conditions was successfully carried out on different mixtures. The best germination result was obtained for soil based on the content of energy sludge instead of fly ash from coal or biomass combustion. The decisive factors limiting the germination process were pH and electrical conductivity values. Soil substitutes with EC ≤ 6.50 mS-cm-1 were the most promising for plant growth.

Finally, three selected soil substitutes, consisting of 900 tons of coal by-products (energy sludge, aggregates and sealing material), 200 tons of decarbonization lime and 580 tons of spent mushroom compost, were used in a polygon test to cover the waste stored in the Janina waste heap. Xerophytic and thermophilic plant species, meadow vegetation, as well as shrubs were planted on an area of 4000 m².

The results of this study have shown a promising opportunity for the use of artificial soil substitutes in the reclamation process of the affected mining areas. A positive effect on seed germination, seedling growth, root initiation, root growth, shoot development and the concentration of macronutrients (N, P, K, Mg, Ca, S and Na) and organic matter in the soils was observed after 9 months of planting. In addition, the soil substitutes used are able to neutralize the high acidity of the residues stored in the Janina waste heap.

 

Acknowledgement

This project is financially supported by the Research Fund for Coal and Steel (Grant Agreement No. 847205-RECOVERY-RFCS-2018 07/2019-06/2023) and the Polish Ministry of Science and Higher Education (Contract No. 847205 z 17.04.2019 5036/FBWiS/2019/2 z 17.12.2019) under the project RECOVERY “Recovery of degraded and transformed ecosystems in coal mining-affected areas”.

The authors are grateful for their support.

 

References

[1] ENVIRONMENTAL PROTECTION AGENCY. 1994. Acid Mine Drainage Prediction. Technical Document EPA 530-R-94-036, Washington DC, 1-52

[2] KLOJZY-KACZMARCZYK, B., MAZUREK, J., STASZCZAK, J. 2016. Analysis of the quality of waste from coal mining in relation to the requirements for inter mining waste. Mineral Resources Management, 95, 227–242

[3] SZCZEPANSKA J., TWARDOWSKA I. 1999. Distribution and environmental impact of coal-mining wastes in Upper Silesia, Poland. Environmental Geology 38, 3, 249–258.

[4] KIRBY, B.M., VENGADAJELLUM C.J., BURTON S.G., COWAN D.A. 2010. Coal, Coal Mines and Spoil Heaps. In: Timmis, K.N. (eds) Handbook of Hydrocarbon and Lipid Microbiology. Springer, Berlin

[5] BAUEREK, A., BEBEK, M., FRĄCZEK, R., PAW, K., KASPERKIEWICZ W. 2017. Variability of chemical composition of acidic runoff waters from an active spoil heap of mining wastes representing sediments of the Cracow Sandstone Series of the Upper Silesian Coal Basin. Przegląd Geologiczny 65: 450–458

[6] EUROPEAN STANDARD. 2020. Soil quality - Determination of the toxic effects of pollutants on germination and early growth of higher plants (EN ISO 18763:2016)