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We eat, drink and breathe daily to stay alive. Breathing comes naturally to us, but have you ever paused to consider the components of the air that surround us? The air around us is not just a simple gas we inhale, but rather a mixture of gases that quietly shape nearly everything about our world. From breathing and burning fuel, to climate and even adverse events like acid rain.
In this article, we’ll take a closer look at air and Earth’s atmosphere, starting from the main components of air, to the invisible pollutants that can harm our planet. We’ll explore how acid rain forms, how the ozone layer protects us from harmful UV rays, and how the carbon cycle and greenhouse gases are linked to global warming and climate change. Here, we demonstrate that air is not simply something we take for granted, it’s a key player in the chemistry of our world.
Air constantly surrounds us as we breathe it in, but did you know that it’s a mixture of gases rather than a single substance?
Nitrogen is the most abundant gas in the air, making up 78% of the air we inhale and is most inert (unreactive). Just like the air in our chip bags, nitrogen acts as a “filler” to dilute oxygen so that things do not catch fire too often and quickly!
Oxygen, which is the gas that sustains life, makes up 21% of the air. Every cell in our bodies requires oxygen for respiration and to release energy.
The remaining 1% of air is a mix of carbon dioxide, water vapour, inert gases (helium, neon, argon etc.) and trace gases (methane, ozone, nitrous oxide etc.) While tiny in amount, these gases play important roles in keeping Earth’s systems working! Carbon dioxide is used by plants for photosynthesis to produce more oxygen, while water vapour is responsible for humidity and weather on Earth.
Since the Industrial Revolution and modernisation, humans have pumped massive amounts of unnatural emissions and chemical waste into the atmosphere over the past century. These air pollutants are harmful solid, liquid, or gaseous particles suspended in the air.
Air pollutants can come from either human activities such as combustion in car engines, industrial processes, pesticide use and livestock methane emissions in agriculture). Even nature could contribute to air pollutants like in volcanic eruptions, wildfires and dust storms.
Carbon monoxide (CO) is an odorless and colourless gas produced from incomplete combustion processes, such as in cars or factories. It is highly toxic, as it binds to hemoglobin in your blood to prevent oxygen uptake.
Sulfur dioxide (SO2) is emitted from burning fossil fuels such as in coal mines, or released during volcanic eruptions. It contributes to acid raid, and can cause respiratory issues when inhaled.
Nitrous oxide species (NOx) are produced from high temperature combustion processes, often in car engines and other industrial processes. Like sulfur dioxide, it also contributes to acid raid and photochemical smog.
Particulates are tiny solid or liquid particles suspended in the air. They are produced from activities such as incomplete combustion and construction, and are classified by size such as PM10 (particles less than 10 micrometers in size) and PM2.5 (particles less than 2.5 micrometers in size). Both types of particulates cause respiratory issues and reduced visibility. PM2.5 is particularly dangerous as it is small enough to enter the lungs and bloodstream.
Volatile organic compounds (VOCs) are carbon-containing gases emitted from paints, cleaning supplies and vehicle exhaust. In addition to smelling terrible and causing short-term effects like irritation, nausea and headaches, these gases have been shown to display carcinogenic properties and cause cancer.
Lead compounds are released into the air through burning of leaded fuel. Due to its high neurotoxicity, especially in children, leaded fuel is slowly being phased out. You would notice that many petrol stations state that their fuel is unleaded now, showing that efforts are indeed being made to reduce lead compounds in the air.
Air pollutants are not simply ugly smog, they also drive climate change and cause severe health problems like asthma, lung disease, and even heart conditions. Some pollutants, such as particulates released from wildfires and volcanic ash. travel thousands of kilometres, affecting people far from their source.
Sulfur dioxide and nitrous oxide species are particularly reactive, even as gases floating around in the atmosphere. With water vapour in the air, sulfur dioxide and nitrous oxide species are able to form sulfuric acid and nitric acid, respectively.
These generated acids in the atmosphere fall back onto the Earth as acid rain, acidifying the environment it touches. The pH in lakes, rivers and ground drops to dangerous levels, resulting in the death of wildlife. Even mankind’s creations are not spared, as the highly acidic can easily corrode structures like buildings and statues.
Over time, scientists have learned how to counter the pollution generated by human activities, giving us tools to slow down our planet’s demise.
Catalytic converters are now installed on the exhaust system of nearly every car worldwide. These clever devices convert generated carbon monoxide and nitrous oxide species into less harmful carbon dioxide and nitrogen, using platinum as a catalyst.
Flue gas desulfuration is used to remove sulfur dioxide gas from industrial emissions such as fossil fuel power plants and factories. Sulfur dioxide within flue gas, which is the gaseous product from industrial activities released through chimneys, is reacted with limestone (CaCO3), producing gypsum (CaSO4) and clean gas that is pumped out into the atmosphere.
SO₂ + CaCO₃ → CaSO₄
Not only is sulfur dioxide successfully removed, this process also produces high purity gypsum, comparable to its naturally mined counterpart. This gypsum product can be used in cement production and as a soil additive in agriculture.
Liming is the process of adding lime (calcium-containing materials) to acidified lakes, rivers and soils to increase their pH to safe levels. Several types of lime can be used such as limestone (CaCO3), quicklime (CaO) or slaked lime (CaOH).
When lime is added to acidic water or soil (containing H⁺ ions from acid rain), a neutralisation reaction occurs.
For limestone: CaCO₃(s) + 2H⁺(aq) → Ca²⁺(aq) + H₂O(l) + CO₂(g)
For quicklime: CaO (s) + 2H⁺(aq) → Ca²⁺(aq) + H₂O(l)
For slaked lime: Ca(OH)₂(s) + 2H⁺(aq) → Ca²⁺(aq) + 2H₂O(l)
These are just a few methods developed to counter air pollutants and their effect on the environment. As scientists continue to develop new technology like electric vehicles, the future of the Earth does not seem so bleak after all.
The ozone layer is located within the stratosphere of the earth’s atmosphere, approximately 15 to 35 km above the Earth’s surface. This invisible shield acts as the Earth’s sunscreen, absorbing harmful UV rays and thus protecting us from sunburn, DNA damage and skin cancer.
In the 1980s, researchers discovered that human-made chemicals, particularly chlorofluorocarbons (CFCs), produced from refrigerators and air-conditioners were depleting ozone within the layer. These CFCs react with ozone (O3) to produce oxygen (O2), thus reducing the amount of ozone protecting us from UV radiation.
This thinning of the ozone layer is known as the “ozone hole”, located above Antarctica. Contrary to popular belief, the ozone hole is not over Australia, though Australia faces extreme exposure to UV radiation due to its geography and climate.
Since the discovery of the ozone hole, significant efforts have been made to restore the ozone layer. The Montreal treaty from 1987 worked to phase out ozone depleting substances like CFCs. Many ozone depleting substances are also potent greenhouse gases, so this treaty helped to tackle global warming at the same time. As of now, approximately 98% of ozone depleting substances have been phased out, and the ozone hole is predicted to “heal” by the mid 21st century.
The carbon cycle refers to a continuous process by which carbon atoms travel within the Earth’s soil, atmosphere, oceans, and living organisms. As the carbon cycle is a closed process, the total amount of carbon remains constant on Earth, though its location and form may vary at various points of time.
The key processes regulating the carbon cycle are:
The natural carbon cycle is delicately balanced. However, human activities like burning of fossil fuels and deforestation extract the carbon that has been stored in the earth. This releases carbon rapidly into the air as greenhouse gases like carbon dioxide, resulting in global warming.
Global warming is the long-term rise in Earth’s average temperature primarily driven by human activities, while climate change is the long-term shift in weather, showing the consequences of a warming planet over time.
Many human activities result in the accumulation of greenhouse gases, which trap heat from the sun, in the atmosphere. Burning fossil fuels and agricultural activities release carbon dioxide and methane into the air, while deforestation removes plants that remove these greenhouse gases. Together, such activities result in the increase of greenhouse gasses within the atmosphere.
In addition to rising global temperatures and melting ice caps, climate change also results in extreme weather, such as an increase in typhoons and hurricanes. Desertification results in the loss of arable land, causing a decrease in food supply. Accumulated carbon dioxide causes acidification of oceans when it dissolves into water bodies. These events eventually result in ecological disruption, where natural habitats are no longer hospitable and animals either change their migratory patterns or face extinction.
Despite the bleak outlook of the Earth, there are still many ways you can do your part to save our planet! Everyone can contribute to lowering greenhouse gas emissions into the air by opting for more environmentally friendly options such as renewable energy or energy efficient appliances. Reforestation efforts by governments and activists increase the number of plants to reabsorb carbon dioxide, while scientists continue to develop carbon capture technologies (like the catalytic converter).
Air pollution and climate change are serious problems. But remember that small actions multiply when millions of people do them together. Every time you save energy, plant a tree, or choose public transport, you’re helping to protect the air we breathe and the carbon cycle that keeps Earth alive.
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Prepared by: Michelle
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