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Один факт - случайность. Два - преднамеренность. Три - тенденция (В. Солоухин)

Abstract

Introduction

Relevancy

The coal industry of Ukraine and in particular, Donbass is a vital component of the national economy and industrial production. The coal industry makes a weighty contribution into operation of the country’s metallurgical industry by cocking coals, sector of thermal power production at the account of steam coal, as well as provides chemical industry with raw materials and energy carriers [1]. The main wastes at coal extraction are overburden and host rocks, which form multiple waste heaps.

Today, more than 140 rock heaps are located within Donetsk occupying the area of about 10 million m2. The quantity of wastes located in the heaps is 600 million t [2].

Thus, the problematic of inspecting rock heaps is conditioned by the double contradictory nature, which determined complexity in rationalization of approaches to coal waste management. On the one hand, they refer to facilities representing ecological danger because harmful emissions in the air of the adjacent territories occur in the process of combustion, oxidation and weathering of rock mass. The whole range of components within the dispersion halo concentrates in the topsoil, which has a considerable impact on geochemistry of underground waters at the next stage of hydrogenous migration, worsens the conditions of plants growing and reduces the animal population. On the other hand, rock heaps can be considered as secondary raw materials.

That is why systematic observations of the contamination indices and ore components in the area of the rock heaps’ exposure are important scientific and practical investigations.

Connection of Work with Scientific Programs, Plans, Topics

The materials received by the author in cooperation with PGE "Artemovsk Hydrogeological Party" when fulfilling individual items of the Program on Environmental Measures of Local Character in the city of Donetsk for the period of 2008, 2009, 2010 and 2011, were taken as a basis. The master’s paper is connected with the Program on Waste Management in Donetsk Oblast for the period of 2011–2015. The Strategy of Solid Domestic Waste, Industrial and Harmful Waste Management in the Territory of Donetsk City corresponds to this topic. The Strategy has been developed for the period of 2005-2020.

Purpose and Tasks of Investigations

The purpose of the scientific and research paper is determination of the role and place of rock heaps in the ecosystem of the city.

The primary tasks, herewith, are as follows:

Object of the Investigation

The object of the environmental and geochemical investigation is rock heaps and areas of their impact being within the city of Donetsk.

Subject of the Investigation

Mineralogical-and-petrographic and ecological-and-geochemical peculiarities of waste pile debris, soils, water-containing rocks and atmospheric air.

Methods of the Investigation

Scientific Novelty of Obtained Results

The scientific novelty is determined by the fact that:

Practical Value of the Paper

The practical value lies in a complex geological and ecological assessment of debris from the position of assessment of the environmental safety of the territories that are adjacent to the heaps and resource value of wastes contained in them, which allows determining soundly the degree of the environmental safety of the adjacent territories. The investigation results allow considering some rock heaps as perspective for getting alumina.

Personal Contribution of the Author

The author took part in the field operations of the heaps’ inspection and debris sampling, performed processing, analysis and systematization of data on the mineralogical and geochemical peculiarities of debris, typification of rock heaps as to the oxidation and burning processes, as well as assessment of the prospectivity of extracting ore components from coal wastes.

Scientific Publications and Approbation of the Paper Results

The following was published according to the materials of carried out investigations:

1. Analysis, Systematization and Generalization of Previous Investigation Materials

A considerable volume of different materials on rock heaps was accumulated. The scientific and research papers of Alekhin V.I., Miulya P.S., Proskurnya Yu.A., Vyborov S.G., Panov B.S., Zborshchik M.P., Osokin V.V. [3-8] contain the ecological, geochemical, mineralogical and petrographic peculiarities of the coal mines’ rock heaps. All researchers concur that rock heaps constitute the environmental hazard, occupy a considerable territory of the city and can serve as secondary raw materials.

It is considered that the environmental hazard of rock heaps is conditioned by the processes of rock mass burning. Today, the mechanism of rock mass self-combustion has been studied in detail; the actions for fire fighting and prevention from burning sources have been developed. Veselovskiy V.S., Alekseyeva N.D., Vinogradova L.P., Saranchuk V.I., Skochinskiy A.A., Ogiyevskiy V.M. [9-11] consider that the sole reason of coal self-combustion is its interaction with the atmospheric air oxygen. However, there is an expression in the paper of Stadnikov L.G. [12] of one of Leibig specialists, which concerns the fact that black coal self-combustion is conditioned by content of iron sulphide in it in the finely dispersed form and the presence of water and air is the closest condition of self-combustion.

Veselovskiy V.S., Alekseyeva N.D., Vinogradova L.P. established [9], that the process of self-heating is initiated by biochemical oxidation, in which microorganisms take part [6].

Sedimentary strata of the Carbonic period having a rather definite geochemical specialization prevail in the rock heaps of Donetsk City. It is considered that germanium, uranium, rare metals, chalcophylic elements can be in the increased concentrations in these deposits [13].

Determination of the perspectives of using the rock heaps as secondary raw materials for extraction of useful components was considered in the papers of Panov B.S., Alekhin V.I., Migulya P.S., Arbatov A.A., Astakhov A.S., Laverov N.P., Tolkachev M.V., Tumanova Ye.S., Tsibizov A.N. et al. There is a big amount of data on the perspectives of using rock heaps for getting alumina (Al2О3), Ge, Sc, Ga, Y, V, Ni etc. [3-5, 14, 15].

The department "Mineral Resources and Environmental Geology" of DonNTU carried out during the last years the comprehensive investigations of some waste piles in the city of Donetsk for the purpose of detecting possible directions of using rocks from these heaps. The results of these investigations certify that rocks of these waste piles suit for producing expanded clay, fill grounds and fertilizers.

2. Natural Conditions of the Investigated Territory

Climate

The main climatic factors of migration and localization of contaminants are the temperature mode of the territory, quantity and composition of atmospheric precipitations, wind direction and speed.

Stratigraphy and lithology

Deposits of medium and upper carbon covered by quaternary and Paleogenic deposits take part in the geological structure of the area. In the western part of the area, rocks of Triassic and Cretaceous period occur on the washed out surface.

Outcrops of lower black coal deposits are traced in the southern outskirts of Donetsk-Makeyevka area.

Medium black coal deposits, correspondingly, occur on lower carbon surface.

Conformability on rocks of the suite С27 and sharp reduction of coal content degree is typical for upper black coal deposits.

Mesozoic deposits occur on the washed out surface of carbon with clear angular displacement.

Paleogene and neogene deposits occur in the north and west of the area with sharp displacement on the washed out surface of the Mesozoic and Paleozoic.

Quaternary deposits cover the region area almost everywhere [16].

3. Classification of Rock Heaps and Determination of Factors and Processes of Exposure on the Geological Environment

Today, more than 140 rock heaps are located within Donetsk City occupying the area about 10 million m2. The height of the coal mines’ rock heaps varies within 8-124 m.

Typification of heaps by a number of signs was made in this paper.

As to thermal state rock heaps are divided in fiery, extinct and non-fiery. A considerable share of operating rock heaps is fiery – 28 of 32. Among waste piles that were put out of operation 25 are fiery and 81 are non-fiery or extinct.

As to morphology mine heaps are divided into:

As to availability of reclamation they are divided into:

Rock mass as a component of the geological environment represents technogenic precipitations; it is in an unbalanced state and under exposure of internal and external factors and it undergoes regular transformations, which are determined by the notion of diagenesis. At the same time, the leading transformation role belongs to aerobic and anaerobic microorganisms at active participation of meteoric waters.

A temporary and permanent water saturation zone is formed in the body of the rock heaps. Herewith, loam soils, alluvial clays or clay coatings of weathering occurred in the foundation of the heap serve as a water-right stratum for the formed technogenic water-bearing horizon. The upper part of the water saturation zone is oxygen-rich, which promotes oxidation processes with heat emission in the presence of high concentration of sulfide sulphur and organic substance.

The temperature exposure on the rock heaps is accompanied mainly by their burning out and baking. The rock mass combustion process more rarely leads to melting.

Oxidation changes of debris without considerable temperature exposure are spread most widely.

Actively burning rock heaps represent the biggest environmental hazard. In the process of carried out investigations traces of oxidation processes appeared in the form of emissions of fresh fumaroles sulfate mineralization are observed in all investigated heaps even without apparent burning sources.

The anaerobic processes of waste piles’ rock mass transformation appear in the lower part of the water saturation zone.

The whole aggregate of the debris transformation processes represents the environmental hazard. The oxidation processes are accompanied by emission of different oxides, sulfuric acid vapors, volatile compounds of metals and toxic elements. The anaerobic processes are accompanied by emission of ammonia, hydrogen sulfide. At the same time the aerobic and anaerobic processes with different degrees of activity can occur simultaneously in one heap.

The investigation of the heap surface allows dividing them by the temperature mode, previous processes of oxidation and combustion. The highest temperatures (more than 800оС) that cause rock melting were established at Putilovskya Mine and No. 1 Panfilovsksya Mine (Fig. 1).

Heap of sh. Putilovskya. In the sample claystones clearly manifested layer-by-layer melting. Products melting in a porous material

Figure 1 – Heap of sh. Putilovskya. In the sample claystones clearly manifested layer-by-layer melting. Products melting in a porous material

Focal burning of rock mass accompanied by baking and lithification of rock wastes was established in the significant part of heaps. The signs of such level of temperatures(200-800оС) were established in the following heaps: mine named after F. Kon, No. 1 Mine Mariya, mine named after Kalinin No. 7-8, etc.

About a half of the investigated heap surfaces, even in the presence of deep cuts of the top and slopes, does not detect any signs of active rock mass burning. The following heaps have the similar signs: mine Vladimir, No. 4 mine named after Gorkiy.

The heaps of the mine Tsentralno-Zavodskaya and No. 1 mine Shverinka can be marked out in connection with insignificant processes of rock mass oxidation.

4. Methods of Carrying out Environmental and Geochemical Works

Today, there are no rock mass sampling methods. That is why, the methods of taking lithochemical samples were used at sampling [17]. These methods provide for sampling taking into account the structural and substance signs of rocks. Sampling, herewith, was made on a definite grid from a definite site at taking site samples. Site samples are taken at studying site isometric structures or soft mixed natural or technogenic formations. Sire samples are made of several point samples. The final sample weight should exceed 1 kg. Site samples were taken from different parts of the waste piles.

A total of 100 lithochemical samples were taken from the surface of 29 heaps according to the program.

5. Assessment of Rock Heaps Influence on the Environment Components

Distribution of 42 chemical elements in debris was studied according to the data on 100 samples taken from 29 heaps in the process of the carried out investigations. In order to determine the regularities of chemical elements’ distribution in the marked out litho- and petro-types samples corresponding to different types of rocks were executed. The whole aggregate of samples was divided into the following groups: conditionally primary mudstone of dark-grey black color (35 samples); mudstone from the operating oxidation zone with fumaroles mineralization precipitations, soaking and incrustation (16 samples); oxidated and burnt tile-red rocks (36 samples); bedizened lumpy mudstone – tonmattes (13 samples).

As a result of processing in the pointed out petro-types a single-type geochemical range and numerically close level of elements’ concentration was established (Table 1).

Table 1. Average Clarks concentration to the elements calculated by sampling samples of different types of rock formations and by breed storage in General

Rock mass Black mudstone черные Zone of oxidation Red mudstone Mottled mudstone Clarks average
Pb 1,49 1,76 1,41 1,48 1,5
V 0,81 0,79 0,81 0,79 0,81
Ga 0,59 0,63 0,64 0,6 0,62
Ni 0,97 1,01 0,96 1 0,98
Cr 1,32 1,27 1,28 1,32 1,3
Ge 0,69 0,7 0,68 0,75 0,7
Co 0,97 0,97 0,99 0,97 0,98
Bi 4,89 4,93 5,19 4,86 5
Be 0,71 0,71 0,71 0,71 0,71
Nb 1,64 1,73 1,72 1,71 1,69
Mo 0,87 0,9 0,95 0,89 0,91
Sn 1,39 1,36 1,39 1,34 1,38
Li 0,57 0,63 0,59 0,57 0,58
Cu 1,01 1,18 1,08 1 1,06
Zr 1,01 0,99 1,05 1,01 1,02
Yb 1,2 1,2 1,2 1,2 1,2
Y 0,62 0,6 0,62 0,62 0,62
La 0,4 0,39 0,4 0,41 0,4
Ti 0,92 0,91 0,91 0,98 0,92
Mg 0,63 0,66 0,66 0,7 0,65
Mn 0,82 0,82 0,84 0,82 0,83
Ca 2,2 2,32 2,3 2,4 2,28
Zn 1,5 1,5 1,67 1,67 1,58
Sc 0,6 0,6 0,59 0,62 0,6
Ag 0,27 0,28 0,26 0,47 0,29
B 0,46 0,41 0,41 0,41 0,43
Hg 0,74 0,8 0,86 0,67 0,79

The main factors of impact on the geological environment of the territories that are adjacent to the rock heaps are air and water migration of waste components. In the process of air migration dispersion halos are formed in soils around the waste piles. In the process of water migration hydrogenic displacement halos are formed in the zone of aeration and upper part of the water saturation zone.

The halo of the atmospheric air contamination is established in the zones of the heaps’ influence with burning and oxidation sources, which is manifested by the growth of concentration of dust, sulfur dioxide, nitrogen dioxide, hydrocarbon oxide and hydrogen sulphide.

As a result of air migration of emissions’ components the contamination halo is formed in soils of the adjacent territories. The MPC excesses are observed for Pb, As, Cd, Zn, Mo, Hg, Cu, SO42-.

Water migration of wastes components starts inside the heap body; this is promoted by the debris transformation processes. These halos control anomalous concentrations of a wide range of toxic elements: Cd, Pb, Cu, Zn, Mo, As, Hg, Bi.

Scheme of the negative impact of waste dumps on the environment

Figure 2 – Scheme of the negative impact of waste dumps on the environment

6. Assessment of Debris Perspectives as Secondary Raw Materials

Traditionally, when studying rocks heaps, investigations of the possibility to use them as secondary raw materials for useful components extractions are carried out.

50 samples were taken for studying distribution of alumina in debris. 37 samples of those taken for determination of alumina content were represented by oxidated mudstones and 13 samples by tonmattes.

The obtained results allowed dividing the rock heaps by alumina concentration in mudstones composing them. The least concentrations of alumina (11.7%) were established in mudstones of the heap of mine No. 3 Tramparkovaya. The alumina content in the main part of the heaps is at the level of 20-25%. Only in some samples the alumina concentrations exceeded 25%: sample 28 (25.22%, heap No. 2 of the mine named after Gorkiy); sample 37 (26.26%, heap No. 1 of the mine Panfilovskaya); sample 83 (25.22%, heap No. 1 of the mine Zaperevalnaya); samples 33 and 35 (25.48% and 29.90%, correspondingly, heap No. 1 of the mine Mariya); sample 94 (29.40%, heap No. 2 of the mine No. 4 Livinka). The ratio of the heap rock mass with the definite alumina concentration is given in the diagram (Fig. 1).

Diagram of the Ratio of the Heaps’ Rock Mass Quantity according to the Levels of Al<sub>2</sub>O<sub>3</sub> Concentraion

Figure 3 – Diagram of the Ratio of the Heaps’ Rock Mass Quantity according to the Levels of Al2O3 Concentraion

The quantity of wastes with the alumina concentration more than 20% within the investigated heaps reaches 87 million t. About 20 million t of alumina are concentrated in them.

The physical and mechanical properties of burnt rocks allow using them in construction, installation of pavements, motor roads, and lower layer of double-layer foundations for asphalt-concrete coatings.

All above-stated certifies the necessity to continue works in studying the substance composition of the waste piles in the city of Donetsk for the purpose of making a rational scheme of accumulated environmentally hazardous wastes processing, which will allow solving two important tasks – improvement of the environmental situation in the city and involvement of readily available and cheap mineral raw materials into production.

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