You live your life mostly in nitrogen – without even thinking about it
Nitrogen is by far the largest component of the air you breathe – without doing much directly. Yet it is essential for all life on Earth.
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What is air? We usually think of two components when we talk about the atmosphere that surrounds us.
Oxygen is the obvious component most people think of. This is the gas that fuels our bodies. Breathing brings oxygen into the body, and our lungs ensure that the oxygen is absorbed into our blood.
The oxygen is transported to the brain, muscles, and organs while the body ensures that carbon dioxide leaves the bloodstream and is exhaled by the lungs. Carbon dioxide is perhaps the second thing that comes to mind when talking about the atmosphere because of its role in global warming.
But the atmosphere contains only about 20 per cent oxygen. Just one-fifth of what you draw into your lungs is oxygen.
Almost unlimited quantities of nitrogen
Carbon dioxide only makes up about 0.04 per cent of the Earth’s atmosphere. Although it occurs in relatively small amounts, it is nevertheless a very important greenhouse gas because it traps solar heat radiation in the atmosphere.
But what makes up the rest of what you breathe, live in, and feel around you? It's primarily nitrogen. A whole 78 per cent of the air is nitrogen, according to NASA.
“There’s an absurd, nearly limitless amount of nitrogen in the atmosphere," Dag Hessen tells sciencenorway.no. He is a biologist and professor at the University of Oslo.
But what has the nitrogen in the atmosphere done for you lately?
Seemingly nothing – and yet essential for life
“Nitrogen has no direct impact on us,” says Erik Sveberg Dietrichs, a doctor and professor of pharmacology.
He is also an author and wrote the book På livets grense (On the edge of life), which explores what happens to the body under extreme conditions.
When you breathe nitrogen into your lungs, it mostly just gets inhaled and then expelled again. You might swallow some, which later comes out as flatulence or a burp. But otherwise, not much happens.
Nitrogen in the atmosphere is simply not very interested in reacting with other elements. It is often described as inert, meaning it does not react with other substances.
Oxygen, on the other hand, reacts extremely easily – which is one of the reasons wood burns and petrol ignites in an engine here on Earth.
But atmospheric nitrogen is bonded with two nitrogen atoms in a stable bond. This bond is so strong that it is only broken by highly specialised microorganisms that form the foundation for all other life on Earth.
But we'll return to that.
Because the nitrogen in the air can be very dangerous under the right conditions.
Into the depths – but not too far
Divers are forced to deal with nitrogen because conditions change dramatically just by moving slightly below the ocean surface.
Nitrogen is the cause of several diving-related ailments.
“When the pressure increases, nitrogen can dissolve in the bloodstream,” says Dietrichs.
In normal atmospheric pressure, nitrogen is not bound in the blood – an example of the fact that humans are adapted to live in a rather narrow zone of the Earth's surface and atmosphere.
Below a depth of around 10 metres, nitrogen starts to get absorbed in the bloodstream if the diver has a normal air mix in the tank.
If the diver descends deeper than 30 metres, the nitrogen in the blood can cause a peculiar intoxicating effect, called nitrogen narcosis.
This condition can be dangerous, leading to unconsciousness and irrational behaviour.
Nitrogen in the blood can also cause decompression sickness, or ‘the bends’. When a diver ascends too quickly as the pressure decreases, bubbles of nitrogen gas begin to form in the blood. The gas, which was dissolved in the blood, accumulates where it shouldn't.
“The bubbles act like blood clots and can create massive blockages of blood vessels,” Dietrichs says.
This can cause pain throughout the body, often affecting the joints. The bends can also lead to death and paralysis if parts of the brain do not receive enough blood.
The solution to this is to take breaks and perform a controlled ascent to the surface, so that the nitrogen in the blood has the opportunity to escape through breathing before it builds up.
Dietrichs notes that nitrogen compounds also have various functions in the body when using medications.
One of the best-known is nitroglycerin, which is taken as a pill that is placed under the tongue for heart problems. This medication releases nitric oxide, which causes the blood vessels to dilate, improving blood flow and reducing the workload on the heart, says Dietrichs.
But nitrogen is also absolutely fundamental for life to exist.
The building block of life
Even though we do not notice or use atmospheric nitrogen, it is still an extremely important element for life on Earth.
Nitrogen is one of the building blocks of DNA and a critical component of amino acids that form proteins. So it is absolutely crucial for life as we know it to exist.
But nitrogen is entirely dependent on a few types of microorganisms that specialise in binding atmospheric nitrogen and converting it into ammonium, which plants can make use of.
“We place very little importance on these microorganisms, but without them, neither we nor other life would exist,” Hessen tells sciencenorway.no.
These organisms are part of the nitrogen cycle on Earth. Plants absorb nitrogen that continues through the food chain. We get nitrogen from meat, eggs, milk, or certain plants.
And other microorganisms in other parts of the cycle also release N2 back into the atmosphere.
However, human activity is also a significant source of nitrogen in nature, which has more than doubled the amount of nitrogen entering the cycle, says Hessen.
A great experiment
The world is becoming greener, and this is directly linked to both greenhouse gas emissions and human use of nitrogen.
“We’ve intervened in the nitrogen cycle in a tremendous way,” says Hessen.
He explains that humans release large amounts of nitrogen into nature in several different ways. When we burn coal, oil, and gas, N2 is converted into oxygen-nitrogen compounds. These are released into the atmosphere and can be absorbed by plants.
Manure from livestock and artificial fertilisers for agriculture are also important sources of nitrogen. Fertilisers are a very important part of modern agriculture. They are also a large part of Norwegian industrial history, which saw chemists Birkeland and Eyde develop the method for using nitrogen that is already present in the atmosphere, according to the Great Norwegian Encyclopedia (link in Norwegian).
This method takes nitrogen from the air and converts it into forms that plants can use, allowing for larger crop yields than would otherwise be possible.
“But fertiliser runoff from farmland causes problems with nutrient pollution in water,” says Hessen.
More plants also mean more carbon is captured, which is positive in terms of reducing greenhouse gas emissions, says Dag Hessen.
At the same time, the use of artificial fertilisers leads to the release of another nitrogen compound – nitrous oxide. This is a highly potent greenhouse gas that is much more effective at trapping heat than carbon dioxide.
So, the next time you fill your lungs with (mostly) nitrogen, take a moment to think about it.
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Translated by Ingrid P. Nuse
Read the Norwegian version of this article on forskning.no
