Air Pollutant Metal: What's The Source?

Mercury is a toxic heavy metal and air pollutant that is released into the atmosphere during the combustion of coal. It is found naturally in coal and, when burned, is released as vapour-phase atomic mercury or bound to particles. Mercury in the atmosphere can have serious environmental and health implications, affecting both aquatic life and human health.

Mercury released from coal combustion

Mercury is a toxic heavy metal that occurs naturally in coal. When coal is burned, mercury is released into the atmosphere. Mercury can enter the atmosphere bound to particles or as vaporised atomic mercury.

In addition to health risks, mercury emissions contribute to environmental issues. Mercury released from coal combustion can lead to water pollution and issues such as acid rain and smog. It can also affect plant growth and yield.

To reduce mercury emissions, various methods have been proposed, including the use of high-rank coals, selective mining of coal, coal washing, fuel switching, and post-combustion removal of mercury from power plant stack emissions. According to the USGS, coal cleaning can remove an average of 37% of mercury. Flue gas controls, such as sorbent injection and hydrothermal treatment technologies, are also being evaluated as possible economic solutions for mercury reduction.

Lead, a heavy metal found in the Earth's crust

Lead is a naturally occurring element found in small amounts in the Earth's crust. It is a heavy metal with a high atomic number of 82 and a relatively low melting point. Lead is soft and malleable, and when freshly cut, it has a shiny grey colour with a hint of blue. However, when exposed to air, it tarnishes to a dull grey.

Lead has been recognised as a toxin for centuries, with lead poisoning acknowledged in the time of Augustus Caesar. It is toxic to humans and animals and affects almost every organ and system in the body. It is particularly dangerous to children, who absorb a higher proportion of lead into their bodies and excrete less of it than adults.

Lead has a variety of applications, the largest of which is in the manufacture of storage batteries. It is also used in ammunition, as a constituent of solder, type metal, bearing alloys, fusible alloys, pewter, and in the shielding of nuclear reactors and X-ray equipment. Lead compounds are used in roofing, electric cables, water pipes, and conduits for corrosive substances.

Lead may enter the environment from these applications and from human activities such as the use of fossil fuels, industrial facilities, and past uses of lead-based paint in homes. Almost half of all refined lead is recovered from recycled scrap.

Health risks of mercury exposure

Mercury is a toxic heavy metal that occurs naturally in coal. When coal is burned, mercury is released into the atmosphere as a pollutant. Mercury can enter the atmosphere bound to particles or as vapour-phase atomic mercury. Once in the atmosphere, it can settle on land and in water bodies, where it can be transformed into methylmercury, a highly toxic compound that accumulates in fish and can enter the human food chain.

Methylmercury is an organic compound that people are exposed to when they eat fish and shellfish. Exposure to large amounts of methylmercury during pregnancy can cause brain damage to the developing fetus. Most healthcare providers recommend limiting fish intake or removing it from the diet during pregnancy.

Inorganic mercury can cause damage to the gastrointestinal tract, the nervous system, and the kidneys. High exposure to inorganic mercury can result in muscle weakness. Elemental (metallic) mercury is mainly harmful when inhaled as a vapour, where it can be absorbed through the lungs. Higher exposures can cause kidney effects, respiratory failure, and even death.

Mercury is also considered a neurotoxin, a substance known or suspected to be poisonous to nerve tissue. Mercury exposure can have toxic effects on the nervous, digestive, and immune systems, as well as the lungs, kidneys, skin, and eyes. Mercury has been traditionally used in medical devices, such as thermometers and blood pressure measurement devices, and in dental amalgam fillings. Human exposure can occur through inhalation of vapours, ingestion of contaminated water or food, or direct contact with mercury or mercury-containing products.

Other air pollutants released from coal combustion

Mercury is the primary metal air pollutant released from coal combustion. However, coal combustion also releases other harmful pollutants, including:

Sulfur Dioxide (SO2)

Sulfur dioxide is a significant contributor to acid rain, which has detrimental effects on the environment. It is also linked to respiratory illnesses and can lead to hospital admissions and emergency room visits. Additionally, sulfur dioxide contributes to the formation of smog.

Nitrogen Oxides (NOx)

Nitrogen oxides play a crucial role in the formation of smog and are associated with respiratory illnesses. They are also correlated with adverse effects on cardiovascular health. Higher concentrations of nitrogen oxides in cities have been linked to increased death rates, suggesting their potential impact on mortality.

Particulate Matter (PM)

Particulate matter includes fine particles of fly ash and dust expelled from coal-burning power plants. These particles are of particular concern due to their small size, which allows them to be inhaled deeply, bypassing the lungs' natural defences. PM2.5, a type of fine particulate matter, has been associated with various adverse health effects, including respiratory and cardiovascular issues, in both children and older adults. It is also known to impact ecosystems, including plants, soil, and water quality.

Carbon Dioxide (CO2)

Carbon dioxide is the primary greenhouse gas produced from burning fossil fuels, including coal. It contributes significantly to the overall damage costs of air pollution and is a key driver of climate change.

The release of these pollutants from coal combustion has far-reaching consequences for both human health and the environment, highlighting the importance of implementing measures to reduce and mitigate their impacts.

Mercury's impact on aquatic life

Mercury is a toxic heavy metal that is released into the atmosphere during the combustion of coal. It is a naturally occurring metal found primarily in a mineral called cinnabar, which can contain up to 86% mercury. Mercury has been a well-known environmental pollutant for several decades, with human activities increasing the amount of mercury emitted and deposited in the atmosphere.

Once released into the environment, mercury can be converted into methylmercury by microorganisms in the soil and aquatic environments. Methylmercury is a highly toxic compound that accumulates in fish and other aquatic organisms, leading to bioaccumulation and biomagnification. This process occurs because the organic form of mercury, methylmercury, is more bioavailable than other forms and is quickly absorbed and slowly excreted. As a result, mercury can build up in the bodies of aquatic organisms over time, leading to potential health risks.

The accumulation of mercury in fish can have significant impacts on aquatic life. High levels of mercury in fish can make them unsafe for human consumption, as mercury is a potent neurological poison that can cause serious health issues in humans. The consumption of contaminated fish can lead to mercury poisoning, which can be both unpleasant and potentially fatal.

In addition to the direct impacts on fish, mercury contamination can also affect other aquatic organisms and ecosystems. Mercury can be absorbed by various aquatic animals through branchial respiration and feeding, leading to bioaccumulation and potential health risks for these species. The complex relationships between biotic and abiotic factors in aquatic systems further contribute to the spread of mercury contamination.

Overall, mercury released into the atmosphere from the combustion of coal has significant impacts on aquatic life. The conversion of mercury to methylmercury increases its toxicity and potential for accumulation in aquatic organisms. The build-up of mercury in fish and other aquatic species can lead to health risks for both humans and the affected organisms, highlighting the importance of addressing mercury pollution to protect aquatic ecosystems and human health.

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