Elsevier

Chemosphere

Volume 284, December 2021, 131397
Chemosphere

The impact of saline mine water on fate of mineral elements and organic matter: The case study of the Upper Silesian Coal Basin

https://doi.org/10.1016/j.chemosphere.2021.131397Get rights and content

Highlights

  • Environmental changes of sediments wereevaluated.

  • Mn, Sr, Ba were evaluated as the most concerning elements.

  • Barite was found as a new precipitated mineral from the mine water.

  • The sorption capacities of the samples increased with the carbon content.

  • The mineral admixtures (feldspars) enhanced the sorption capacity.

Abstract

The work presented here provides a complex environmental impact of sediments in vicinity to the area of the former Lazy coal mine site in the Upper Silesian Coal Basin (Czech Republic). The main aim of this work has been to determine the degree of contamination, to describe the organic matter, and to carry out sorption isotherms to see the size and distribution of pores in the monitored sediments that are the crucial parameters to assumption of removal mechanisms of elements carried in mine water. The results show that the greatest enrichment of Mn, Sr, Ba, and was in sediments of the first tens of meters from the mine water discharge sediments. Ba and Sr were precipitated as mineral barite and thus formed a dominant insoluble component in the river sediments, which were further carried by water flow towards the water reservoirs. Predominant amounts of fossil material and smaller quantities of carbonized and recent organic matter were altered by weathering and erosion processes. The coal materials have a relatively beneficial sorption capacity, which increases with the carbon content. The overburden waste should be considered for use in removing heavy metals in-situ.

Introduction

Coal mining and coal processing have a great impact on the environment, leading to extensive destruction of the land, extinction of wildlife, and deterioration of water quality. However, the excavation of large quantities of rock (gangue) material has provided access to ore bodies that are profitable for economic use. Coarse-grained sediments (overburden) are segregated, and may be used in various ways, for example in construction activities at the mine site (Haibin and Zhenling, 2010). Sulphide minerals usually oxidize in waste rock piles, and high levels of sulphates are becoming mobile in the natural streams as a result of washing them out from the waste rock piles. To reduce oxidation, toxicity and erosion, mine wastes must be isolated and must be disposed of safely. Otherwise, the waste acts as a major source of metals, acidity or radioactivity (Blowes et al., 2003; Bondaruk et al., 2015).

For over 100 years, the Lazy mine (Ostrava-Karviná coalfield) was a location where intensive underground mining of hard coal deposits took place (Fig. 1). The coalfield is embodied in the Czech part of the Upper Silesian Coal Basin which extends from the Czech Republic into Poland (Kandarachevová et al., 2009). The mining area covers about 600 ha, from which over 145 million tons of coal were extracted. Coal-bearing rock was mined from complete strata of the Karviná Formation (Carboniferous), which were overlain by thick Neogene and Quaternary sediments (Dopita and Kumpera, 1993).

Exploitation of the coal mine ended in 2019, and the area is now under disposal treatment. The study area is nowadays covered by isolated open-cut tailing ponds drained by the Stružka stream. The sedimentary cover in these ponds consists of various coarse to very fine-grained sediments, mainly composed of crushed coal, sand, silt, and mud. The tailing ponds were constructed to dilute the mine water running from deep underground. The rising mine water is highly alkaline, originating from a mixture of the original brine (Pluta and Zuber, 1995), residual water, and sewage water with unclear chemical composition. The mining industry is considered to be the leading source of salination in freshwater environments (Leppänen et al., 2019).

Saline mine water is defined as mildly mineralized to strongly mineralized, according to the level of total mineralization (TDS) and high concentrations of Na+, Cl, SO42−, NH4+, K+, Ca2+, Mg2+, Fe2+, Fe3+, and Ba2+ (Harat et al., 2015). Highly mineralized mine water is found in the active mining areas and post-mining areas in the Polish parts of the basin. Formerly, mine water was directly discharged into the Olza River, resulting in degradation of the water quality. In an attempt to reduce the degradation, the Olza collector, with an overflow into the Oder River, was constructed to collect saline mine water. The Oder is a significant recipient of industrial, sewage and diluted saline mine waters drained by the Stružka stream (Policht-Latawiec, 2015; Sracek et al., 2010).

Any sediment forms a natural sink for binding metals from the water column via adsorption, co-precipitation or chemisorption processes. The sorption potential of the sediment may vary depending on various factors, such carbon content, mineral matter content, or volume of micropores (Řimnáčová et al., 2020). The larger molecules (for example heavy metals) adsorb on the surface of the micropores and lower sizes of mesopores. Considering that the CO2 molecule have the diameter 0.33 nm and in studied materials, it is captured mainly by physical adsorption in the smallest micropores. Physical adsorption is caused by van der Waals forces between an adsorbate molecule and the adsorbent surface (Suzuki, 1990).

Optical microscopy is able to categorize both organic (fossil, recent) and also components which undergo thermal changes (carbonized). This categorization, in combination with geochemical data provides, crucial information when assessing the environmental burden on man-changed localities (Sýkorová et al., 2016; Vöröš et al., 2018). A combination of geochemical, textural and petrographic approaches were used in a study of hazardous materials, with a view to evaluating the sorption potential of the materials for removing heavy metal(oid)s, such, Cu, Zn, Pb, Ni, As. The main aim of this study is to make an environmental assessment of the sediments in the recultivated area of the former Lazy Mine, using geochemical, petrographical and textural approaches.

Section snippets

Description of samples

Five samples of sediments composed mostly of coal tailings and material of coal waste piles were collected within the area of the former Lazy coal mine in December 2019 (Fig. 1). Starting Point 1 (sample MW-2) was characterized by the saline mine water running from the pipeline forming a narrow-cut stream. Very fine-grained sediments had been deposited in the stream bed. The water temperature measured at this point was 15.8 °C, the conductivity was 22700 μS/cm, and pH = 7.5. Point 2 (sample

Proximate and ultimate analysis

The proximate and ultimate analysis illustrated the variability of the samples that were studied (Table 1). The ash content (Aa) was greatly variable (ranging between 30.9 and 89.8 wt%) and decreased with an increasing carbon content (3.4–53.4 wt%). The samples of sediments showed a variable volatile (Va) matter content, varying from 7.1 to 21.4 wt%, and also varying calorific values (Qid = 1.5–21.2 MJ/kg). The nitrogen (Nd) content varied from 0.2 to 1.0 wt%, and the hydrogen (Hd) content

Element enrichment

Numerous approaches to the study of hazardous materials have attracted great attention for their potential use in removing heavy metals (Liu et al., 2007; Rahman, 2020). To assess the degree of contamination, enrichment factors (EF) have been calculated to enable a comparison with naturally-occurring values quantified for continental crust (Wedepohl, 1995) and hard coal in the basin of the Polish coal mining sites (Parzentny, 2020). The enrichment factor has recently been applied for assessing

Conclusions

Sediments from former coal mine have been investigated and have been characterized geochemically and petrographically. The monitored sediments were assessed to be enriched by variable amounts of Mn, Sr, Ba, (between extremely enriched and very severely enriched). The element enrichment depends on the time since the deposition of sediments that are in contact with saline mine water. Barium (Ba) and Sr sulphates and feldspars were observed to be an important mineral matrix found at CON-1, where

Credit Author Statement

Dominik Vöröš: Investigation, Conceptualization, Original draft writing, Data Curation, Visualization, Writing - Review & Editing:. Daniela Řimnáčová: Data Curation, Writing - Review & Editing:. Lujza Medvecká: Data Curation, Writing - Review & Editing:. Eva Geršlová: Supervision, Writing - Review & Editing:. Mercedes Díaz-Somoano: Writing - Review & Editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This study was financially supported by the Czech Academy of Science within the Research and Mobility Support of Starting Researchers Programme (Project No. MSM 100462001, under the title Vanadium Migration in Coal Mining Areas: Sorption of V on Selected Clay Minerals). The authors also thank the ERASMUS + programme for supporting PhD student Lujza Medvecká with a research fellowship at RWTH Aachen University, Germany, and we thank Ivana Perná and Lenka Borecká for their aid in the laboratory

References (37)

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