Coal's Watery Grave: Pollution's Dark Legacy

Coal is a major source of water pollution, with coal mines and power plants heavily impacting lakes, rivers, streams, and drinking water supplies. The process of mining and burning coal releases a range of pollutants, including heavy metals, mercury, and other toxins, which can contaminate nearby water sources. This is known as acid mine drainage and can change the pH of streams to the same level as vinegar. Additionally, coal plants can cause thermal pollution by discharging heated water back into natural water bodies, decreasing fertility and increasing heart rates in fish. The waste produced by coal plants, such as coal ash and sludge, is often disposed of in unlined ponds or landfills, which can leak and poison freshwater sources. Coal dust has also been found to cause physical ecological harm, impairing the ability of plants to photosynthesize.

Coal mining and mountain removal

Coal mining, particularly surface mining, has a devastating impact on the environment, including water pollution. Mountaintop removal is a highly destructive form of coal mining that involves clearcutting forests and removing vegetation from entire mountains, which are then flattened with explosives to uncover thin coal seams. This process leaves behind desolate lands incapable of supporting wildlife. The resulting debris is dumped into the valleys below, burying more than 2,000 miles of headwaters.

The debris and coal dust from mountaintop removal can contaminate nearby rivers, lakes, and aquifers. This is known as acid mine drainage and occurs when certain substances, typically iron sulfide (FeS2) or fool's gold, are oxidized after being exposed to air and water. The resulting highly acidic water contains heavy metals like arsenic, copper, lead, and cadmium, which are toxic to humans and wildlife. This changes the pH of nearby streams to the same level as vinegar and can render waterways unusable for drinking and recreation.

In addition to the direct contamination of waterways, mountaintop removal can also impact water quality through increased sedimentation. Without vegetation to anchor the soil, precipitation can carry away loose topsoil into nearby waterways. The increased sediment can kill fish and plants, clog streams, and disrupt their natural flow, further decreasing the available aquatic habitat.

The impact of mountaintop removal on water quality can be severe and persist for decades after mining has ceased. A study of reclaimed coal mines in the Canadian Rockies found increased levels of selenium, lead, carbon, nitrogen, and polycyclic aromatic compounds in downstream water sources. Another study in Israel found that snails in the Mediterranean near a power plant were harmed by the presence of coal in the water, likely due to elevated levels of cadmium.

The coal industry and power plants have contributed to water pollution through coal ash and waste products. More than 100 million tons of coal ash are produced by coal-fired power plants in the United States each year, and about a third of that waste is reused, often in concrete. The rest is stored in unlined ponds, abandoned mines, or hazardous landfills, from which heavy metals can escape into nearby waterways and contaminate drinking water. Coal ash spills, such as the 2014 spill into North Carolina's Dan River, further highlight the risks of coal ash storage and its impact on water pollution.

Coal ash and sludge

Coal ash is the grey powder-like substance that is left behind after coal is burned. It contains concentrated amounts of toxic elements, including arsenic, lead, mercury, chromium, lithium, radium, selenium, and other heavy metals. These contaminants can pollute waterways, groundwater, drinking water, and the air if not properly managed.

Improper disposal and discharge of coal ash have caused widespread environmental and economic damage to nearby waterways and properties. In 2000, a coal slurry impoundment in Kentucky failed, releasing over 300 million gallons of thick black sludge into rivers and streams—30 times more than the Exxon-Valdez oil spill. In 2014, 39,000 tons of coal ash spilled into North Carolina's Dan River. Six years earlier, more than 5 million cubic yards of coal ash were released into Tennessee's Emory River, one of the largest environmental disasters in US history.

The US Environmental Protection Agency (EPA) has established national rules for coal ash disposal and is working to strengthen existing controls on water discharges. Coal ash is disposed of or utilised in various ways, depending on the type of byproduct, the plant's processes, and the regulations the power plant must follow. Some power plants dispose of coal ash in surface impoundments, landfills, or mines, which can contaminate groundwater. Others discharge it into nearby waterways under their water discharge permits.

Recycling and reusing waste products from coal burning, such as coal ash, can help reduce environmental impacts. Coal ash can be recycled into products like concrete, wallboard, and synthetic gypsum. However, the industry has been slow to adopt these practices, and most coal ash continues to be disposed of in ways that can contaminate water sources.

Thermal pollution

Coal power plants use water to cool down the equipment. This process is known as "once-through" and involves pumping water directly from a water source, heating it up, and then discharging it back. The waste water is typically hotter (by up to 20-25° F) than the water source, creating "thermal pollution". This thermal pollution can have a range of negative impacts on the environment.

Firstly, thermal pollution can decrease the level of dissolved oxygen (DO) in the water. This decrease in DO levels can be harmful to aquatic animals such as fish, amphibians, and copepods. It can also increase the metabolic rate of these organisms, leading to increased food consumption and potentially causing food source shortages and a sharp decrease in population.

Secondly, thermal pollution can create prime growing conditions for bacteria that harm native fish habitats. This has been observed at the Monroe Power Plant in Michigan, where thermal pollution kills millions of fish and fish eggs each year. Additionally, heated water from industrial sources can impact the migration patterns of aquatic organisms, leading to competition for resources and compromising food chains.

To address thermal pollution, the Clean Water Act (CWA) requires the EPA to ensure that cooling water intake structures reflect the best technology available for minimizing adverse environmental impacts, including thermal pollution. However, industries are concerned about the high costs associated with retrofitting cooling towers to meet these requirements.

It is important to note that "wet-recirculating" plants can avoid thermal pollution by cooling and reusing water. However, these systems consume more water due to losses during the cooling process.

Acid mine drainage

AMD can have pH values as low as -3.6, and often contains high concentrations of solutes, including iron, arsenic, cadmium, lead, copper, nickel, and other heavy metals. These elevated levels of heavy metals can only be dissolved in waters with a low pH, as found in the acidic waters produced by pyrite oxidation. The amount of AMD released depends on the size of the extracted rock volume, exposed surface area, and the concentration and type of contained sulphides.

AMD severely impacts the environment, with devastating effects on biological activity in many streams. It can discolour water and smother plant and animal life on the streambed, disrupting stream ecosystems. Aquatic macroinvertebrates living in streams affected by AMD show fewer individuals, less diversity, and lower biomass. Many species of fish are also unable to tolerate the pollution.

While measures have been implemented to minimise the effects of AMD, it still occurs in abandoned mines and a small percentage of new mines. In the United Kingdom, for example, discharges from abandoned mines are often exempt from regulatory control. However, innovative solutions, such as constructed wetlands, have been implemented to mitigate the impacts of AMD on the environment.

Coal dust

Another study in 2006 evaluated 22 years of coal dust dispersal around the Westshore Coal Terminal, located just north of the US border. It found widespread coal dust on the surface of the water near the terminal, observing a film of fine coal particles floating on the water 200 meters east of the vessel loading dock.

Ahrens and Morrissey identified several studies that examined the effects of coal dust pollution on fish and shellfish. They found that most of the studies were old, poorly designed, or inconclusive. For example, a 1963 study showed that coal washery solids in relatively low concentrations reduced the growth rate of exposed trout. An even older study from the late 1930s linked fish mortality to the irritation caused by coal particles entering a freshwater stream. A 1979 study by an EPA researcher found that PAH contamination from coal reduced the spawning success of fathead minnows from 90% to 36%.

In addition to the physical presence of coal dust, there is also a potential chemical pollution risk. A study in Canada found that coal in the water can be a source of acidity, salinity, trace metals, hydrocarbons, chemical oxygen demand, and potentially, macronutrients. These factors pose hazards to aquatic organisms, such as increasing the risk of invasive species taking hold.

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