Environmental Effects
Iron hydroxide precipitate stains a stream receiving acid drainage from surface coal mining. Environmental issues can include erosion, formation of sinkholes, loss of biodiversity, and contamination of soil, groundwater and surface water by chemicals from mining processes. In some cases, additional forest logging is done in the vicinity of mines to increase the available room for the storage of the created debris and soil. Besides creating environmental damage, the contamination resulting from leakage of chemicals also affects the health of the local population. Mining companies in some countries are required to follow environmental and rehabilitation codes, ensuring the area mined is returned to close to its original state. Some mining methods may have significant environmental and public health effects.
4.3.1 Mining Accidents
Safety has long been a controversial issue in the mining business especially with sub-surface mining. While mining today is substantially safer than it was in the previous decades, mining accidents are often very high profile, such as the Quecreek Mine Rescue saving 9 trapped Pennsylvania coal miners in 2002. Mining ventilation is a significant safety concern for many miners. Poor ventilation of the mines causes exposure to harmful gases, heat and dust inside sub-surface mines. These can cause harmful physiological effects, including death. The concentration of methane and other airborne contaminants underground can generally be controlled by dilution (ventilation), capture before entering the host air stream (methane drainage), or isolation (seals and stoppings). Ignited methane gas is a common source of explosions in coal mines, or, the more violent coal dust explosions. Gases in mines can also poison the workers or displace the oxygen in the mine, causing asphixiation. For this reason, the MHSA requires that workers have gas detection equipment in groups of miners. It must be able to detect common gases, such as CO, O2, H2S, and % Lower Explosive Limit. Additionally, further regulation is being requested for more gas detection as newer technology such as nanotechnology is introduced.
4.3.2 Health Problems
High temperatures and humidity may result in heat-related illnesses, including heat stroke which can be fatal. Dusts can cause lung problems, including silicosis, asbestosis and pneumoconiosis (also known as miners lung or black lung disease). A ventilation system is set up to force a stream of air through the working areas of the mine. The air circulation necessary for the effective ventilation of a mine is generated by one or more large mine fans, usually located above ground. Air flows in one direction only, making circuits through the mine such that each main work area constantly receives a supply of fresh air.
Miners utilize equipment strong enough to break through extremely hard layers of the earth's crust. This equipment combined with the closed workspace that underground miners work in, can cause hearing loss. For example, a roof bolter (commonly used by mine roof bolter operators) can reach sound power levels of up to 115 dB. Combined with the reverberant effects of underground mines, a miner without proper hearing protection is not only at a high risk for hearing loss, but is also going against OSHA standards.
4.3.3 Cave-Insand Abandoned Mines
Since mining entails removing dirt and rock from its natural location creating large empty pits, rooms and tunnels, cave-ins are a major concern within mines. Modern techniques for timbering and bracing walls and ceilings within sub-surface mines have reduced the number of fatalities due to cave-ins, but accidents still occur. The presence of heavy equipment in confined spaces also poses a risk to miners, and in spite of modern improvements to safety practices, mining remains dangerous throughout the world.
There are upwards of 560,000 abandoned mines on public and privately owned lands in the United States alone. Abandoned mines pose a threat to anyone who may attempt to explore them without proper knowledge and safety training. Old mines are often dangerous and can contain deadly gases. Since weather may have eroded the earth and rock surrounding it, the entrance to an old mine in particular can be very dangerous. Old mine workings, caves, etc. are commonly hazardous simply due to the lack of oxygen in the air, a condition in mines known as blackdamp.
Exercise 19 Make a list of threats to people health caused by mining industry. Discuss suggestions for solving environmental problems.
Exercise 20 Define whether the statements are true or false. 1. Mining ventilation is an important safety concern for many miners. 2. The concentration of methane and other airborne contaminants underground can generally be controlled by ventilation. 3. Gases in mines can also poison the workers or displace the oxygen in the mine, causing heat stroke. 4. Dusts can cause heart problems, including silicosis, asbestosis and pneumoconiosis 5. Air flows in several directions, making circuits through the mine such that each main work area constantly receives a supply of fresh air. 6. A ventilation system is set up to force a stream of air through the working areas of the mine. 7. The minerals are concentrated using sluices or jigs. 8. The presence of heavy equipment in confined spaces doesn’t pose any risk to miners 9. Modern mining sector of the industry is dominated by individual entrepreneurs or small business 10. Environmental issues can include erosion, formation of sinkholes, loss of biodiversity, and contamination of soil. Exercise 21 Match the equipment to its function.
Exercise 22 Unscramble these words and find their synonyms
Exercise 23 Cross the odd word out
Exercise 24 In pairs discuss the following questions.
1. Why doesmining remain dangerous throughout the world? 2. What is the most important safety issue in mining? 3. What problems do dust and temperature cause? 4. What are the two sectors of mining industry? 5. What do environmental issues include?
5 MINERAL PROCESSING
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