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Evaluation of Air Pollution as a Result of Coal Exploitation in Roşiuţa Coal Pit

Evaluation of Air Pollution as a Result of Coal Exploitation in Roşiuţa Coal Pit Revista Minelor – Mining Revue ISSN-L 1220-2053 / ISSN 2247-8590 vol. 28, issue 1 / 2022, pp. 66-72 EVALUATION OF AIR POLLUTION AS A RESULT OF COAL EXPLOITATION IN ROȘIUȚA COAL PIT 1 2* Ioan DUMITRESCU , Ciprian NIMARĂ University of Petroșani, Petroșani, Romania,oni.dumitrescu@gmail.com University of Petroșani, Petroșani, Romania, ciprian.nimara@yahoo.com DOI: 10.2478/minrv-2022-0006 Abstract: The polluting activity carried out by the coal exploitation in Roşiuţa coal pit has effects on the environment and the main pollution sources of the atmosphere are: suspended powders, particulate matter and burning gases. The pollutants contain substances with different degrees of toxicity. Through the measurements performed "in situ", for the dust concentration at different points, it was found that the indices of the maximum concentration (MC-mg/m /air), on the mining areas, were according to the legislation in force. At some points, the dust concentration is higher, but as the distance increases, the pollution is no longer felt, so it can be noticed that the lignite exploitation has a local influence. Keywords: air pollution, coal pit, sterile dump, coal yard, Roșiuța 1. Introduction Roşiuţa mining perimeter is located in the North of Oltenia, on the territory of Gorj County, occupying the Northeastern side of Motru mining basin under the administration of Roşiuţa Mining Exploitation, within Motru Coal Mining Exploitation. The appearance of the relief is given by the alternation of high profile isolated hills and dividing valleys that widen in the confluence area, giving the appearance of a small depression (confluence between Ploştina Creek and Motru River, confluence between Peşteana Creek and Motru River). The average altitude of the relief is between 200-300 m and the highest being Pâlvei Peak of 415 m to the North-East of Roşiuţa village, Motru town being located at an altitude of 185 m. The lowest elevation is 171 m in Meriş meadow located upstream of Broşteni commune. The whole relief is given by the high peaks in the North East sector with a rounded appearance and the valleys that widen towards the confluence. It should be noted that in the last 40-45 years, all these landscapes have undergone an increasingly strong anthropogenic pressure, some of which are in advanced stages of degradation. Geological research undertaken in the North-Western part of Oltenia in the period 1950-1960 highlighted the existence of important lignite reserves in the meadow area of Jiu, Jaleş and Tismana, located at a shallow depth, with average discovery reports of 2 - 3 m / ton, possibly capitalized by up-to-date mining works. 2. Areas with the highest risk of air pollution and pollution sources The change of air quality, caused by coal exploitation in Roşiuţa coal pit, materializes through the increase, in certain areas, of the concentration of particulate matter resulting from machinery operations. The most important areas where pollution can be noticed are: - Excavation areas; - Sterile dump areas; - Discharge points of the front lanes on the connecting lanes; - Distribution nodes; - When dumping the coal in the coal yard and its shipment; - On the roads towards the coal pit. Corresponding author: Ciprian Nimară, Lect. PhD., University of Petroșani, Petroșani, Romania, contact details (20, University str., Petroșani, 332006, Romania, ciprian.nimara@yahoo.com) 66 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 Another potential source of air quality deterioration is the self-ignition of coal from deposits. Due to incomplete combustion, carbon dioxide and small amounts of sulfur dioxide, light hydrocarbons - toxic substances whose concentrations do not usually exceed the permitted limits, are released into the air. Oxidation of stored coal results in a loss of calorific value relative to the fuel mass [1]. Atmospheric emissions from Roşiuţa coal pit are of two categories: emissions from combustion processes and direct emissions from technological processes (table 1). a) Emissions from combustion processes come from: - Mobile sources (vehicles, means of transport); - Surface sources (excavators). b) Emissions from technological processes come from three sources: - Mobile sources (conveyor belts); - Surface sources (excavators); - Fixed sources (coal deposits). Table 1. Sources of air pollution related to the studied area Process phase Type of emission source Emission Car traffic Ground linear with Flue gases from daily traffic on site (transport vehicles) undirected emissions Coal excavation Ground surface with Flue gases from the construction machinery (front and sterile undirected emissions excavators) Particulate matter due to coal excavation and sterile dumping Coal transport Ground linear with Particulate matter due to coal and sterile transport and sterile undirected emissions Coal and sterile storage Ground surface with Particulate matter due to coal and sterile storage undirected emissions The main sources of air pollution caused by mining exploitation may be considered: fixed equipment according to the “Continuous flow extraction technology with high capacity equipment” and mobile equipment related to: - Material processing at working points; - Discontinuous flow operation with classic equipment and car transport; - Development and strip superstructure; - Development and superstructure of technological and access roads; - Rehabilitation works / machinery operation; - Landscaping. 2.1. Fixed equipment The coal exploitation in Roşiuţa coal pit is the main source of air pollution with dust. Also, it can be noticed the low mechanical strength and low humidity (in the summer) of friable rocks, which lead to dust making. The areas of dusty air pollution are: a) Rotor excavator working area In the case of the cross-sectional block excavation method in the forward direction, during the cutting operation, bucket spillages, on the excavator belt number 1 and further in the lane relay until the discharge on the main flow strip, a large amount of dust. The flocculation of the deposited dust is influenced by meteorological causes, the quantity and quality of the excavated rocks, the distance from the emissary, so that the pollution from the neighboring areas can be temporarily important [2]. Other sources of dust are the falling rocks on the slope during the mining works, the material from buckets on the belt and crushing lumps. Excavation area is relatively isolated from the human settlements (the households of Runcurelu village located in the Northwestern limit of the excavation works will be relocated). b) On the way of conveyor belt Dust is formed when the coal is discharged from one lane to another. The high concentration of dust made by coal transport is influenced by: - Low humidity; - Low rain; 67 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 - High transport speed; - The height of fall on the pick-up belt. These areas are far away from villages, except for the route of sterile transport lanes in the inner dump corresponding to Lupoaia mining perimeter and the coal transport route located in the Western side of the perimeter, at least 200 m from the inhabited area of Roşiuţa village. c) Discharge at production points (concentration of production) There is also the concentration of production of all technological lines in the flow, in the distribution node, which increases the concentration of dust. These areas are far away from villages. d) In the coal yard The coal yard serving the coal pit is located near the main road. The coal, to the distribution node is transported on the transport circuit consisting of conveyer belts located on the floor of the coal pit as well as on the bench which connects the distribution node and the excavation bench. The coal is transported on the tap line, from the distribution node, consisting of conveyor belts in fixed construction, to the coal yard, located in the Western side of the coal pit at about 50-100 m from the coal yard of Roşiuţa village. The coal is dumped in the coal yard by ASG and KSS type machines and the shipment to the loading point is made by KSS type machine. In addition to the factors listed above that lead to the formation of dust, there is also the taking of coal from the conveyer belt and its discharge from about 5-10 m high. The monitoring of the air quality indicators carried out by Gorj and Mehedinti Environmental Protection Agencies in the adjacent area to the coal yard reflects exceeding values of the maximum allowed concentrations for sediment dusts and particulate matter. e) Sterile dump During the analyzed period, the sterile dump is made in the inner dump of Roşiuţa mining perimeter, the inner dump of Lupoaia mining perimeter and the outer dumps of Valea Ştiucani, Valea Potângu and Valea Cireşului. According to the working norms, the excavation, transport and dump installations used in Roşiuţa mining perimeter must be equipped with mobile installations for spraying the access areas during the summer, when the dust concentration increases. 2.2. Mobile equipment Suspended powders, particulate matter and burning gases are the main pollutants. Dust is formed in the case of the material and spare parts supply at the working point on the technological flow with cars, on the access roads to the coal pit, which if not sprayed with water is a danger to the health of the staff who work in the area. Table 2. Emission agents for the main elements of the flue gases No. Pollutant Measure unit Emission factor 1 NOx 48.8 2 NM-VOC 7.08 3 CH 0.17 4 CO g/kg of diesel 15.8 5 NH 0.007 6 N O 1.3 7 PM 5.73 8 Cadmium 0.01 9 Copper 1.7 10 Chrome 0.05 11 Nickel 0.07 12 Selenium 0.01 13 Zinc 1 14 Benz - a - anthracene μg/kg of Diesel 80 15 Benzo (b) - fluoranthene 50 16 Dibenzo (a, h) anthracene 10 17 Benzo (a) pyrene 30 18 Chrysene 200 19 Fluoranthene 450 20 Phenanthene 2500 68 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 Emissions of dust and gases specific to the machinery activity are assessed by the consumption of fuels and the area on which these activities take place (pollutants, particulate matter and sediments). It is estimated that air pollution in the activities of refueling, maintenance and repair of means of transport is reduced and can be neglected. The mobile equipment involved in the coal exploitation will generate emissions like: NOx, SO , CO, CO , CH and NMVOCs. 2 4 According to the simple methodology, the following emission factors, presented in the tables 2, 3 and 4, can be applied to the analyzed situation: For the transport activity performed with transport equipment larger than 3.5 tons and using Diesel fuel, the emission agents are presented in the tables below. Table 3. Emission agents Emission agent NO CH VOC CO N O PM CO X 4 2 2 gr / km 10.9 0.06 2.08 8.71 0.03 800 gr / kg of Diesel 42.7 0.25 8.16 34.2 0.12 4.3 3138 gr / MJ 1.01 0.006 0.19 0.80 0.003 73.9 Table 4. Emission agents for heavy metals in flue gases No. Pollutant Measure unit Emission agent 1 Cadmium 0.01 2 Copper 1.7 3 Chrome 0.05 μg/kg of used Diesel 4 Nickel 0.07 5 Selenium 0.01 6 Zinc 1 Mobile emission sources like diesel engines which produce exhaust gases in the atmosphere contain the whole complex of pollutants specific to the internal combustion of diesel: nitrogen oxides, non-methane volatile organic compounds, methane, carbon oxides, ammonia, heavy metal particles, polycyclic aromatic hydrocarbons and sulfur dioxide. The complex of pollutants emitted into the atmosphere through the exhaust gases contains substances with different degrees of toxicity. Thus, in addition to common pollutants (NOx, SO , CO, particles), there are substances with carcinogenic potential highlighted by epidemiological studies conducted under the auspices of the World Health Organization [3], namely: cadmium, nickel, chromium and polycyclic aromatic hydrocarbons (PAHs). It is also noted the presence of nitrous oxide (N O) - a substance incriminated in the depletion of the stratospheric ozone layer - and methane, which, together with CO have global effects on the environment, being greenhouse gases. The amount of pollutants emitted into the atmosphere by machinery depends mainly on the following factors: - Engine type; - Engine power; - Fuel consumption per unit of power; - Machine capacity; - Age of engine / machinery. Pollutant emissions decrease the more advanced the engine performance, the trend in the world being the manufacture of engines with the lowest possible consumption per unit of power and with the most restrictive control of emissions. Moreover, these two elements are reflected in the dynamics of both EU and US legislation in the field. For the conveyance, the above assessments regarding the correlations between the pollutant emissions and the technological level of the engine, the fuel consumption per unit of power or per 100 km, the age of the vehicle are also valid. The equipment (excavator, bulldozer, front loader, and tractor) moves over short distances in the work area and there is an even distribution of emissions across the work areas. Maximum pollutant concentrations are achieved within this area. Dispersion studies completed with measurements show that, outside this area, the concentrations of air pollutants are substantially reduced. Thus at 20 m outside this strip the concentrations are reduced by 50% and at over 50 m the reduction is 75%. Along the transport route, the distribution of pollutants is considered uniform. From a chemical point of view, the dispersion is the result of the reactive characteristic of the air under the influence of solar radiation, atmospheric humidity, variability of thermal 69 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 regime and turbulent phenomena through which the air is contacted with the soil and water surface, generating additional chemical interactions [4]. The resulting emissions have a strictly local effect in the area of the work fronts with effect within the perimeter of the coal pit, where the provisions of STAS 12574/87 "Air in protected areas" do not apply. 2.3. Coal ignition Coal ignition is a process of slow oxidation in contact with air, being an exothermic phenomenon that can affect coal yards and outcrops in the coal pit. The observations made over time on the coal yards in the mining perimeters of Oltenia region regarding the behavior of the stored coal, led to the conclusion that the time interval favorable to self-ignition is from 30 to 90 days from the date of storage. Oxidation is rapid during this period and later the coal tends to stabilize its oxidation rate at a lower level. At the same time, it was found that the spontaneous oxidation of coal takes place in five distinct stages: - Up to 48.7 ° C, the coal slowly absorbs oxygen from the air. The temperature continues to rise and when it reaches 76.6 ° C, favorable conditions for self-ignition occur in a time interval of approx. 72 hours; - Oxygen absorption increases with stack temperature up to a range of 100-137.7 ° C; - At 137.7 ° C, the carbon dioxide is removed with water vapor; - The elimination of carbon dioxide continues to a temperature of 232.2 °C, at this temperature the coal ignites spontaneously; - At 366.6 ° C the coal begins to burn. The oxidation process, in addition to the appearance of fire nuclei, results in gaseous emissions of methane, ethane, carbon monoxide, sulfur dioxide, nitrogen dioxide, hydrochloric acid and polycyclic aromatic hydrocarbons. In order to be able to remove this undesirable phenomenon, it is necessary to know a series of aspects, among which the essential ones are both the properties and composition of the stored coals and the environmental factors. The environmental factors that have a greater or lesser influence on the quality parameters of the stored coal for a certain period of time are: - Air temperature; - Ground temperature (at the surface of the deposits); - Relative humidity of the air; - Atmospheric pressure; - Wind action; - Meteorological phenomena (fog, precipitation, snow layer thickness). The characteristics of coals that show a strong tendency to self-ignite are: - High oxidation characteristic rate; - High friability; - The presence of finely divided pyrites. 3. Particulate matter and field sampling Dust is released from the starting point of the cutting operations by the excavator in the coal pit, the dumping of the material from the buckets on the belt conveyor and the dumping from one conveyor to another, in the relay of belts transporting waste and coal. Dumping the sterile in the dump from heights exceeding 20 m, the fall from the height of the material on the arm of the dump machine favors the formation of dust. Through the measurements performed "in situ" (figure 1), for the dust concentration from different points (figure 2), it was found that the indices of the maximum concentration (MC-mg/m /air), on mining areas, were according to the legislation in force (table 5). At some points, the dust concentration is higher, but as the distance increases, the pollution is no longer felt, so the lignite extraction activity has a local influence. Table 5. Particulate matter Results [g/m /month] Maximum Standard Month allowed No. Sampling point of value February March April May reference 2021 2021 2021 2021 1 sample point 1 28.77 35.29 28.68 24.38 STAS 2 sample point 2 15.96 9.25 10.84 14.37 g/m / 12574/1987 month 3 sample point 3 20.70 8.33 10.75 14.93 70 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 Figure 1. Location of Roșiuța coal pit and sample points There are also other activities which produce dust, like coal dumping in coal yards, shipping and loading into wagons. During the use of the access roads in the coal pit, for the materials and spare parts supply at the working points, the conveyance forms dust as well. Sample 3 Sample 2 Sample 1 February March April May Figure 2. Particulate matter (g/m /month) The emissions resulting from the exploitation of lignite in Roşiuţa I perimeter have a local effect in the area of the work fronts [5], inside the coal pit perimeter, where the provisions of STAS 12574/87 and O.M. 592/2002 replaced by Law no. 104/2011, only from the activity of coal storage and dispatch results exceeding the maximum allowed concentrations for sediment and particulate matter in the inhabited area. 4. Conclusions The pollution produced on the environment by the coal exploitation in Roşiuţa coal pit is significant, with effects on the whole environment, including the human community. The environment protection actions and ecological restoration of waste lands in the works carried out in the coal pit area have the role of controlling and limiting the negative effects to ensure the restoration of bad lands to the natural conditions before mining. The effects of the change in air quality, caused by the coal exploitation in Roşiuţa coal pit, can be noticed through the increase, in some areas, of the dust concentration, gas and smoke resulting from the development of the coal pit technology. Considering the technological process of coal exploitation, the sources of air pollution can be considered as the fixed equipment and mobile equipment. 71 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 Dust is formed in the case of the material and spare parts supply at the working point on the technological flow with cars, on the access roads to the coal pit, which if not sprayed with water is a danger to the health of the staff who work in the area. The main pollutants are: suspended powders, particulate matter and burnt gases. Emissions of dust and gases specific to machinery activities are assessed by the consumption of fuels and the area on which these activities take place (pollutants, particulate matter and sediment). Mobile emission sources, regardless of their type, run on diesel engines, the exhaust gases in the atmosphere contain the whole complex of pollutants specific to the internal combustion of diesel engines: nitrogen oxides, non-methane volatile organic compounds, methane, carbon oxides, ammonia, heavy metal particles, polycyclic aromatic hydrocarbons and sulfur dioxide. The main pollutants emitted into the atmosphere by the transport activities contain elements with different degrees of toxicity. Thus, in addition to pollutants like NOx, SO , CO and particles, there are elements with carcinogenic potential highlighted by epidemiological studies conducted by the WHO, namely: cadmium, nickel, chromium and polycyclic aromatic hydrocarbons. Through the measurements performed "in situ", for the dust concentration from different points, it was found that the indices of the maximum concentration (MC-mg/m /air), on mining areas, were according to the legislation in force. At some points, the dust concentration is higher, but as the distance increases, the pollution is no longer felt, so the lignite extraction activity has a local influence. References [1] Bell F. G., Donnelly L. J., 2014 Mining and Its Impact on the Environment, e-book, London, UK [2] Fodor D., 2008 The open pit exploitation of mineral ores and rock deposits, volume I (in Romanian), Editura Corvin, Deva [3] Rod A, 1997 Introduction: Mining and Metals in the Environment, Journal of Geochemical Exploration, Vol. 58 [4] Fodor D., Baican G., 2001 The impact of mining industry on the environment (in Romanian), Infomin Publishing, Deva [5] Dumitrescu I., Nimară C., 2017 The Impact on Residents’ Health Near the Coal Deposit of Rosiuta Coal Pit, Quality - access to success, Vol. 18 (S1) This article is an open access article distributed under the Creative Commons BY SA 4.0 license. Authors retain all copyrights and agree to the terms of the above-mentioned CC BY SA 4.0 license. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Mining Revue de Gruyter

Evaluation of Air Pollution as a Result of Coal Exploitation in Roşiuţa Coal Pit

Mining Revue , Volume 28 (1): 7 – Mar 1, 2022

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Publisher
de Gruyter
Copyright
© 2022 Ioan Dumitrescu et al., published by Sciendo
eISSN
2247-8590
DOI
10.2478/minrv-2022-0006
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Abstract

Revista Minelor – Mining Revue ISSN-L 1220-2053 / ISSN 2247-8590 vol. 28, issue 1 / 2022, pp. 66-72 EVALUATION OF AIR POLLUTION AS A RESULT OF COAL EXPLOITATION IN ROȘIUȚA COAL PIT 1 2* Ioan DUMITRESCU , Ciprian NIMARĂ University of Petroșani, Petroșani, Romania,oni.dumitrescu@gmail.com University of Petroșani, Petroșani, Romania, ciprian.nimara@yahoo.com DOI: 10.2478/minrv-2022-0006 Abstract: The polluting activity carried out by the coal exploitation in Roşiuţa coal pit has effects on the environment and the main pollution sources of the atmosphere are: suspended powders, particulate matter and burning gases. The pollutants contain substances with different degrees of toxicity. Through the measurements performed "in situ", for the dust concentration at different points, it was found that the indices of the maximum concentration (MC-mg/m /air), on the mining areas, were according to the legislation in force. At some points, the dust concentration is higher, but as the distance increases, the pollution is no longer felt, so it can be noticed that the lignite exploitation has a local influence. Keywords: air pollution, coal pit, sterile dump, coal yard, Roșiuța 1. Introduction Roşiuţa mining perimeter is located in the North of Oltenia, on the territory of Gorj County, occupying the Northeastern side of Motru mining basin under the administration of Roşiuţa Mining Exploitation, within Motru Coal Mining Exploitation. The appearance of the relief is given by the alternation of high profile isolated hills and dividing valleys that widen in the confluence area, giving the appearance of a small depression (confluence between Ploştina Creek and Motru River, confluence between Peşteana Creek and Motru River). The average altitude of the relief is between 200-300 m and the highest being Pâlvei Peak of 415 m to the North-East of Roşiuţa village, Motru town being located at an altitude of 185 m. The lowest elevation is 171 m in Meriş meadow located upstream of Broşteni commune. The whole relief is given by the high peaks in the North East sector with a rounded appearance and the valleys that widen towards the confluence. It should be noted that in the last 40-45 years, all these landscapes have undergone an increasingly strong anthropogenic pressure, some of which are in advanced stages of degradation. Geological research undertaken in the North-Western part of Oltenia in the period 1950-1960 highlighted the existence of important lignite reserves in the meadow area of Jiu, Jaleş and Tismana, located at a shallow depth, with average discovery reports of 2 - 3 m / ton, possibly capitalized by up-to-date mining works. 2. Areas with the highest risk of air pollution and pollution sources The change of air quality, caused by coal exploitation in Roşiuţa coal pit, materializes through the increase, in certain areas, of the concentration of particulate matter resulting from machinery operations. The most important areas where pollution can be noticed are: - Excavation areas; - Sterile dump areas; - Discharge points of the front lanes on the connecting lanes; - Distribution nodes; - When dumping the coal in the coal yard and its shipment; - On the roads towards the coal pit. Corresponding author: Ciprian Nimară, Lect. PhD., University of Petroșani, Petroșani, Romania, contact details (20, University str., Petroșani, 332006, Romania, ciprian.nimara@yahoo.com) 66 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 Another potential source of air quality deterioration is the self-ignition of coal from deposits. Due to incomplete combustion, carbon dioxide and small amounts of sulfur dioxide, light hydrocarbons - toxic substances whose concentrations do not usually exceed the permitted limits, are released into the air. Oxidation of stored coal results in a loss of calorific value relative to the fuel mass [1]. Atmospheric emissions from Roşiuţa coal pit are of two categories: emissions from combustion processes and direct emissions from technological processes (table 1). a) Emissions from combustion processes come from: - Mobile sources (vehicles, means of transport); - Surface sources (excavators). b) Emissions from technological processes come from three sources: - Mobile sources (conveyor belts); - Surface sources (excavators); - Fixed sources (coal deposits). Table 1. Sources of air pollution related to the studied area Process phase Type of emission source Emission Car traffic Ground linear with Flue gases from daily traffic on site (transport vehicles) undirected emissions Coal excavation Ground surface with Flue gases from the construction machinery (front and sterile undirected emissions excavators) Particulate matter due to coal excavation and sterile dumping Coal transport Ground linear with Particulate matter due to coal and sterile transport and sterile undirected emissions Coal and sterile storage Ground surface with Particulate matter due to coal and sterile storage undirected emissions The main sources of air pollution caused by mining exploitation may be considered: fixed equipment according to the “Continuous flow extraction technology with high capacity equipment” and mobile equipment related to: - Material processing at working points; - Discontinuous flow operation with classic equipment and car transport; - Development and strip superstructure; - Development and superstructure of technological and access roads; - Rehabilitation works / machinery operation; - Landscaping. 2.1. Fixed equipment The coal exploitation in Roşiuţa coal pit is the main source of air pollution with dust. Also, it can be noticed the low mechanical strength and low humidity (in the summer) of friable rocks, which lead to dust making. The areas of dusty air pollution are: a) Rotor excavator working area In the case of the cross-sectional block excavation method in the forward direction, during the cutting operation, bucket spillages, on the excavator belt number 1 and further in the lane relay until the discharge on the main flow strip, a large amount of dust. The flocculation of the deposited dust is influenced by meteorological causes, the quantity and quality of the excavated rocks, the distance from the emissary, so that the pollution from the neighboring areas can be temporarily important [2]. Other sources of dust are the falling rocks on the slope during the mining works, the material from buckets on the belt and crushing lumps. Excavation area is relatively isolated from the human settlements (the households of Runcurelu village located in the Northwestern limit of the excavation works will be relocated). b) On the way of conveyor belt Dust is formed when the coal is discharged from one lane to another. The high concentration of dust made by coal transport is influenced by: - Low humidity; - Low rain; 67 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 - High transport speed; - The height of fall on the pick-up belt. These areas are far away from villages, except for the route of sterile transport lanes in the inner dump corresponding to Lupoaia mining perimeter and the coal transport route located in the Western side of the perimeter, at least 200 m from the inhabited area of Roşiuţa village. c) Discharge at production points (concentration of production) There is also the concentration of production of all technological lines in the flow, in the distribution node, which increases the concentration of dust. These areas are far away from villages. d) In the coal yard The coal yard serving the coal pit is located near the main road. The coal, to the distribution node is transported on the transport circuit consisting of conveyer belts located on the floor of the coal pit as well as on the bench which connects the distribution node and the excavation bench. The coal is transported on the tap line, from the distribution node, consisting of conveyor belts in fixed construction, to the coal yard, located in the Western side of the coal pit at about 50-100 m from the coal yard of Roşiuţa village. The coal is dumped in the coal yard by ASG and KSS type machines and the shipment to the loading point is made by KSS type machine. In addition to the factors listed above that lead to the formation of dust, there is also the taking of coal from the conveyer belt and its discharge from about 5-10 m high. The monitoring of the air quality indicators carried out by Gorj and Mehedinti Environmental Protection Agencies in the adjacent area to the coal yard reflects exceeding values of the maximum allowed concentrations for sediment dusts and particulate matter. e) Sterile dump During the analyzed period, the sterile dump is made in the inner dump of Roşiuţa mining perimeter, the inner dump of Lupoaia mining perimeter and the outer dumps of Valea Ştiucani, Valea Potângu and Valea Cireşului. According to the working norms, the excavation, transport and dump installations used in Roşiuţa mining perimeter must be equipped with mobile installations for spraying the access areas during the summer, when the dust concentration increases. 2.2. Mobile equipment Suspended powders, particulate matter and burning gases are the main pollutants. Dust is formed in the case of the material and spare parts supply at the working point on the technological flow with cars, on the access roads to the coal pit, which if not sprayed with water is a danger to the health of the staff who work in the area. Table 2. Emission agents for the main elements of the flue gases No. Pollutant Measure unit Emission factor 1 NOx 48.8 2 NM-VOC 7.08 3 CH 0.17 4 CO g/kg of diesel 15.8 5 NH 0.007 6 N O 1.3 7 PM 5.73 8 Cadmium 0.01 9 Copper 1.7 10 Chrome 0.05 11 Nickel 0.07 12 Selenium 0.01 13 Zinc 1 14 Benz - a - anthracene μg/kg of Diesel 80 15 Benzo (b) - fluoranthene 50 16 Dibenzo (a, h) anthracene 10 17 Benzo (a) pyrene 30 18 Chrysene 200 19 Fluoranthene 450 20 Phenanthene 2500 68 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 Emissions of dust and gases specific to the machinery activity are assessed by the consumption of fuels and the area on which these activities take place (pollutants, particulate matter and sediments). It is estimated that air pollution in the activities of refueling, maintenance and repair of means of transport is reduced and can be neglected. The mobile equipment involved in the coal exploitation will generate emissions like: NOx, SO , CO, CO , CH and NMVOCs. 2 4 According to the simple methodology, the following emission factors, presented in the tables 2, 3 and 4, can be applied to the analyzed situation: For the transport activity performed with transport equipment larger than 3.5 tons and using Diesel fuel, the emission agents are presented in the tables below. Table 3. Emission agents Emission agent NO CH VOC CO N O PM CO X 4 2 2 gr / km 10.9 0.06 2.08 8.71 0.03 800 gr / kg of Diesel 42.7 0.25 8.16 34.2 0.12 4.3 3138 gr / MJ 1.01 0.006 0.19 0.80 0.003 73.9 Table 4. Emission agents for heavy metals in flue gases No. Pollutant Measure unit Emission agent 1 Cadmium 0.01 2 Copper 1.7 3 Chrome 0.05 μg/kg of used Diesel 4 Nickel 0.07 5 Selenium 0.01 6 Zinc 1 Mobile emission sources like diesel engines which produce exhaust gases in the atmosphere contain the whole complex of pollutants specific to the internal combustion of diesel: nitrogen oxides, non-methane volatile organic compounds, methane, carbon oxides, ammonia, heavy metal particles, polycyclic aromatic hydrocarbons and sulfur dioxide. The complex of pollutants emitted into the atmosphere through the exhaust gases contains substances with different degrees of toxicity. Thus, in addition to common pollutants (NOx, SO , CO, particles), there are substances with carcinogenic potential highlighted by epidemiological studies conducted under the auspices of the World Health Organization [3], namely: cadmium, nickel, chromium and polycyclic aromatic hydrocarbons (PAHs). It is also noted the presence of nitrous oxide (N O) - a substance incriminated in the depletion of the stratospheric ozone layer - and methane, which, together with CO have global effects on the environment, being greenhouse gases. The amount of pollutants emitted into the atmosphere by machinery depends mainly on the following factors: - Engine type; - Engine power; - Fuel consumption per unit of power; - Machine capacity; - Age of engine / machinery. Pollutant emissions decrease the more advanced the engine performance, the trend in the world being the manufacture of engines with the lowest possible consumption per unit of power and with the most restrictive control of emissions. Moreover, these two elements are reflected in the dynamics of both EU and US legislation in the field. For the conveyance, the above assessments regarding the correlations between the pollutant emissions and the technological level of the engine, the fuel consumption per unit of power or per 100 km, the age of the vehicle are also valid. The equipment (excavator, bulldozer, front loader, and tractor) moves over short distances in the work area and there is an even distribution of emissions across the work areas. Maximum pollutant concentrations are achieved within this area. Dispersion studies completed with measurements show that, outside this area, the concentrations of air pollutants are substantially reduced. Thus at 20 m outside this strip the concentrations are reduced by 50% and at over 50 m the reduction is 75%. Along the transport route, the distribution of pollutants is considered uniform. From a chemical point of view, the dispersion is the result of the reactive characteristic of the air under the influence of solar radiation, atmospheric humidity, variability of thermal 69 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 regime and turbulent phenomena through which the air is contacted with the soil and water surface, generating additional chemical interactions [4]. The resulting emissions have a strictly local effect in the area of the work fronts with effect within the perimeter of the coal pit, where the provisions of STAS 12574/87 "Air in protected areas" do not apply. 2.3. Coal ignition Coal ignition is a process of slow oxidation in contact with air, being an exothermic phenomenon that can affect coal yards and outcrops in the coal pit. The observations made over time on the coal yards in the mining perimeters of Oltenia region regarding the behavior of the stored coal, led to the conclusion that the time interval favorable to self-ignition is from 30 to 90 days from the date of storage. Oxidation is rapid during this period and later the coal tends to stabilize its oxidation rate at a lower level. At the same time, it was found that the spontaneous oxidation of coal takes place in five distinct stages: - Up to 48.7 ° C, the coal slowly absorbs oxygen from the air. The temperature continues to rise and when it reaches 76.6 ° C, favorable conditions for self-ignition occur in a time interval of approx. 72 hours; - Oxygen absorption increases with stack temperature up to a range of 100-137.7 ° C; - At 137.7 ° C, the carbon dioxide is removed with water vapor; - The elimination of carbon dioxide continues to a temperature of 232.2 °C, at this temperature the coal ignites spontaneously; - At 366.6 ° C the coal begins to burn. The oxidation process, in addition to the appearance of fire nuclei, results in gaseous emissions of methane, ethane, carbon monoxide, sulfur dioxide, nitrogen dioxide, hydrochloric acid and polycyclic aromatic hydrocarbons. In order to be able to remove this undesirable phenomenon, it is necessary to know a series of aspects, among which the essential ones are both the properties and composition of the stored coals and the environmental factors. The environmental factors that have a greater or lesser influence on the quality parameters of the stored coal for a certain period of time are: - Air temperature; - Ground temperature (at the surface of the deposits); - Relative humidity of the air; - Atmospheric pressure; - Wind action; - Meteorological phenomena (fog, precipitation, snow layer thickness). The characteristics of coals that show a strong tendency to self-ignite are: - High oxidation characteristic rate; - High friability; - The presence of finely divided pyrites. 3. Particulate matter and field sampling Dust is released from the starting point of the cutting operations by the excavator in the coal pit, the dumping of the material from the buckets on the belt conveyor and the dumping from one conveyor to another, in the relay of belts transporting waste and coal. Dumping the sterile in the dump from heights exceeding 20 m, the fall from the height of the material on the arm of the dump machine favors the formation of dust. Through the measurements performed "in situ" (figure 1), for the dust concentration from different points (figure 2), it was found that the indices of the maximum concentration (MC-mg/m /air), on mining areas, were according to the legislation in force (table 5). At some points, the dust concentration is higher, but as the distance increases, the pollution is no longer felt, so the lignite extraction activity has a local influence. Table 5. Particulate matter Results [g/m /month] Maximum Standard Month allowed No. Sampling point of value February March April May reference 2021 2021 2021 2021 1 sample point 1 28.77 35.29 28.68 24.38 STAS 2 sample point 2 15.96 9.25 10.84 14.37 g/m / 12574/1987 month 3 sample point 3 20.70 8.33 10.75 14.93 70 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 Figure 1. Location of Roșiuța coal pit and sample points There are also other activities which produce dust, like coal dumping in coal yards, shipping and loading into wagons. During the use of the access roads in the coal pit, for the materials and spare parts supply at the working points, the conveyance forms dust as well. Sample 3 Sample 2 Sample 1 February March April May Figure 2. Particulate matter (g/m /month) The emissions resulting from the exploitation of lignite in Roşiuţa I perimeter have a local effect in the area of the work fronts [5], inside the coal pit perimeter, where the provisions of STAS 12574/87 and O.M. 592/2002 replaced by Law no. 104/2011, only from the activity of coal storage and dispatch results exceeding the maximum allowed concentrations for sediment and particulate matter in the inhabited area. 4. Conclusions The pollution produced on the environment by the coal exploitation in Roşiuţa coal pit is significant, with effects on the whole environment, including the human community. The environment protection actions and ecological restoration of waste lands in the works carried out in the coal pit area have the role of controlling and limiting the negative effects to ensure the restoration of bad lands to the natural conditions before mining. The effects of the change in air quality, caused by the coal exploitation in Roşiuţa coal pit, can be noticed through the increase, in some areas, of the dust concentration, gas and smoke resulting from the development of the coal pit technology. Considering the technological process of coal exploitation, the sources of air pollution can be considered as the fixed equipment and mobile equipment. 71 Revista Minelor – Mining Revue vol. 28, issue 1 / 2022 ISSN-L 1220-2053 / ISSN 2247-8590 pp. 66-72 Dust is formed in the case of the material and spare parts supply at the working point on the technological flow with cars, on the access roads to the coal pit, which if not sprayed with water is a danger to the health of the staff who work in the area. The main pollutants are: suspended powders, particulate matter and burnt gases. Emissions of dust and gases specific to machinery activities are assessed by the consumption of fuels and the area on which these activities take place (pollutants, particulate matter and sediment). Mobile emission sources, regardless of their type, run on diesel engines, the exhaust gases in the atmosphere contain the whole complex of pollutants specific to the internal combustion of diesel engines: nitrogen oxides, non-methane volatile organic compounds, methane, carbon oxides, ammonia, heavy metal particles, polycyclic aromatic hydrocarbons and sulfur dioxide. The main pollutants emitted into the atmosphere by the transport activities contain elements with different degrees of toxicity. Thus, in addition to pollutants like NOx, SO , CO and particles, there are elements with carcinogenic potential highlighted by epidemiological studies conducted by the WHO, namely: cadmium, nickel, chromium and polycyclic aromatic hydrocarbons. Through the measurements performed "in situ", for the dust concentration from different points, it was found that the indices of the maximum concentration (MC-mg/m /air), on mining areas, were according to the legislation in force. At some points, the dust concentration is higher, but as the distance increases, the pollution is no longer felt, so the lignite extraction activity has a local influence. References [1] Bell F. G., Donnelly L. J., 2014 Mining and Its Impact on the Environment, e-book, London, UK [2] Fodor D., 2008 The open pit exploitation of mineral ores and rock deposits, volume I (in Romanian), Editura Corvin, Deva [3] Rod A, 1997 Introduction: Mining and Metals in the Environment, Journal of Geochemical Exploration, Vol. 58 [4] Fodor D., Baican G., 2001 The impact of mining industry on the environment (in Romanian), Infomin Publishing, Deva [5] Dumitrescu I., Nimară C., 2017 The Impact on Residents’ Health Near the Coal Deposit of Rosiuta Coal Pit, Quality - access to success, Vol. 18 (S1) This article is an open access article distributed under the Creative Commons BY SA 4.0 license. Authors retain all copyrights and agree to the terms of the above-mentioned CC BY SA 4.0 license.

Journal

Mining Revuede Gruyter

Published: Mar 1, 2022

Keywords: air pollution; coal pit; sterile dump; coal yard; Roșiuța

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