Oxygen: Air Pollutant Or Life-Giver?

Air is a mixture of gases, most of which are naturally occurring, with nitrogen (N2) being the most abundant at about 78% and oxygen (O2) the second-most at 21%. The air also contains human-made air pollutants, which can be harmful to human health and the environment. These pollutants include nitrogen dioxide, carbon monoxide, and sulfur dioxide from vehicle exhaust, as well as nitrogen oxide, which is a component of photochemical smog. While oxygen is not considered a pollutant, it plays a role in the formation of some pollutants, such as ozone and nitrogen oxides.

Oxygen is the second most abundant gas in the air

Air is composed of several gases, the most abundant of which is nitrogen, which makes up about 78% of the Earth's atmosphere. The second most abundant gas is oxygen, which accounts for approximately 21%. Together, these gases create a balanced and stable environment that is essential for life on Earth.

Oxygen is crucial for the process of respiration in most living organisms, including humans and animals, and is also required for combustion. In the troposphere, the lowest layer of the Earth's atmosphere, oxygen plays a role in oxidation reactions that help break down matter and release nutrients into the soil. This layer of the atmosphere also contains water in all three phases (liquid, solid, and gas) as well as solid particles called aerosols.

The amount of water vapour in the air varies depending on location and climate. In hot, humid locations, water vapour can be the third most abundant gas, while in arid or extremely cold regions, it may be nearly absent. The concentration of water vapour also decreases with altitude, with the upper troposphere containing less water vapour than air near the surface, and the stratosphere and mesosphere containing almost none.

In addition to nitrogen and oxygen, other gases are present in the Earth's atmosphere, although in much smaller amounts. These include argon, carbon dioxide, methane, ozone, and water vapour. The atmosphere also contains trace amounts of other gases, such as helium, neon, krypton, and hydrogen. The specific composition of these gases can vary with altitude and location, and they can be influenced by human-made chemicals and pollutants.

Oxygen is not an air pollutant

Air is a mixture of naturally occurring gases and human-made pollutants. The Earth's atmosphere is composed mostly of nitrogen (78%) and oxygen (21%), with trace amounts of other gases such as argon, carbon dioxide, helium, neon, methane, krypton, and hydrogen. While nitrogen does very little in the atmosphere, it is essential for life on Earth. Through the nitrogen cycle, nitrogen enters the soil and water, binds with other elements, and becomes accessible to living things.

Oxygen is likewise essential for life on Earth. Atmospheric oxygen enables cellular respiration in humans and animals, and it facilitates oxidation reactions that help break down matter and release nutrients into the soil.

Ozone, a gas composed of three oxygen atoms, can be found in the upper atmosphere and at ground level. While stratospheric ozone forms a protective layer that shields the Earth from harmful ultraviolet radiation, tropospheric or ground-level ozone is a harmful air pollutant. Ground-level ozone is formed through chemical reactions between oxides of nitrogen and volatile organic compounds. It is the main ingredient in smog and can be harmful to human health, particularly for those with asthma.

Ozone, a gas composed of oxygen atoms, is an air pollutant

Air is a mixture of naturally occurring gases and human-made air pollutants. The most abundant naturally occurring gas in the air is nitrogen, which makes up about 78% of the air we breathe. The second most abundant is oxygen, which makes up about 21% of the air.

Oxygen is not considered an air pollutant. However, ozone, a gas composed of three oxygen atoms, is an air pollutant. It is both a natural and a man-made product that occurs in the Earth's upper atmosphere (the stratosphere) and lower atmosphere (the troposphere). Stratospheric ozone forms a protective layer that acts as a shield from the sun's harmful ultraviolet rays. This "good ozone" has been partially destroyed by man-made chemicals, creating a "hole in the ozone." The good news is that this hole is getting smaller.

Tropospheric or ground-level ozone, on the other hand, is a harmful air pollutant. It is the main ingredient in smog and can cause serious health issues. Ozone aggressively attacks lung tissue and is especially harmful to people with asthma or other pre-existing medical conditions. Research has shown that even short-term exposure to ground-level ozone can cause greater obstruction of airways. Furthermore, long-term exposure to ground-level ozone is associated with increased respiratory illnesses, metabolic disorders, nervous system issues, and reproductive issues.

Ground-level ozone is not directly emitted into the air but is created by chemical reactions between volatile organic compounds (VOCs) and nitrogen oxides (NOx). These reactions typically occur in the presence of heat and sunlight, leading to higher ozone concentrations during the summer months. VOCs are produced by sources such as chemical plants, gasoline pumps, and industrial activities, while nitrogen oxides result primarily from high-temperature combustion in power plants, industrial boilers, and motor vehicles.

Oxygen reacts with nitrogen to form nitrogen oxides, which are air pollutants

Air is a mixture of naturally occurring gases and human-made air pollutants. The most abundant naturally occurring gas in the air is nitrogen (N2), which makes up about 78% of the air we breathe. The second most abundant gas is oxygen (O2), which makes up about 21% of the air.

Oxygen is a highly reactive non-metal, oxidizing agent that readily forms oxides with most elements and other compounds. At room temperature, nitrogen is a very inactive gas. However, in the presence of lightning or a spark, nitrogen combines with oxygen to form several different oxides. Nitrogen monoxide or nitric oxide (NO) and nitrogen dioxide (NO2) are the most abundant. These nitrogen oxides are produced from the reaction of nitrogen and oxygen gases in the air during combustion, especially at high temperatures.

Nitrogen dioxide (NO2) is a reddish-brown gas with a pungent, acrid odour and is one of the several oxides of nitrogen. It is a strong oxidant, corrosive, and poorly soluble in water. At high concentrations, it can cause inflammation of the airways. Breathing in high levels of NO2 can increase the likelihood of respiratory problems, including wheezing, coughing, colds, flu, and bronchitis. Prolonged exposure to high levels of NO2 can cause irreversible damage to the respiratory system.

Nitrogen oxides (NOx) are a collective term for nitrogen monoxide (NO) and nitrogen dioxide (NO2). NOx is a precursor for smog formation and contributes to acid rain and the depletion of the ozone layer. NOx is produced naturally by lightning and by man-made sources, most notably road traffic and energy production.

Oxygen is necessary for human and animal cellular respiration

Oxygen is the second most abundant gas in the atmosphere, making up about 21% of the air we breathe. It is an essential component of human and animal cellular respiration, which is the process by which organisms combine oxygen with foodstuff molecules, converting chemical energy into life-sustaining activities. The final products of cellular respiration are ATP (adenosine triphosphate) and H2O.

The process of cellular respiration can be broken down into three main steps: glycolysis, the citric acid (TCA) cycle or Krebs cycle, and the electron transport chain, where oxidative phosphorylation occurs. While glycolysis can occur in anaerobic conditions, the TCA cycle and oxidative phosphorylation require oxygen. In the oxidative phosphorylation stage, each pair of hydrogen atoms removed from NADH and FADH2 provides a pair of electrons that eventually reduce one atom of oxygen to form water.

The TCA cycle and oxidative phosphorylation are responsible for producing a large amount of the ATP generated during cellular respiration. When oxygen is present, pyruvate oxidation produces one acetyl-CoA, one NADH, and one CO2 per pyruvate molecule. The TCA cycle then yields one GTP, three NADH, one FADH2, and two CO2. NADH and FADH2 can then be used by the electron transport chain to create further ATP as part of oxidative phosphorylation.

Overall, the process of cellular respiration yields around 30-32 ATP per molecule of glucose. This is significantly more than anaerobic metabolism, which produces only 2 molecules of ATP per molecule of glucose. Thus, oxygen is necessary for human and animal cellular respiration as it enables the production of a much greater amount of energy in the form of ATP.

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