Nitrogen is essential to life on Earth. It is a component of all proteins and it can be found in all living systems. Nitrogen compounds are present in organic materials, foods, fertilizers, explosives and poisons. Nitrogen is crucial to life, but in excess it can also be harmful to the environment.
Named after the Greek word nitron, for "native soda," and genes for "forming," nitrogen is the fifth most abundant element in the universe. Nitrogen gas constitutes 78 percent of Earth's air, according to the Los Alamos National Laboratory. On the other hand, the atmosphere of Mars is only 2.6 percent nitrogen.
In its gas form, nitrogen is colorless, odorless and generally considered as inert. In its liquid form, nitrogen is also colorless and odorless, and looks similar to water, according to Los Alamos.
One of the most important nitrogen compounds is ammonia (NH3), which can be produced in in the so-called called Haber process, in which nitrogen is reacted with hydrogen. The colorless ammonia gas with a pungent smell can be easily liquefied into a nitrogen fertilizer. In fact, about 80 percent of ammonia that is produced is used as fertilizer, and it is also used as a refrigerant gas; in the manufacture of plastics, textiles, pesticides, dyes; and in cleaning solutions, according to the New York Department of State.
The nitrogen cycle
The nitrogen cycle, in which atmospheric nitrogen is converted into different organic compounds, is one the most crucial natural processes to sustain living organisms. During the cycle, bacteria in the soil process or "fix" atmospheric nitrogen into ammonia, which plants need in order to grow. Other bacteria convert the ammonia into amino acids and proteins. Then animals eat the plants and consume the protein. Nitrogen compounds return to the soil through animal waste. Bacteria convert the waste nitrogen back to nitrogen gas, which returns to the atmosphere.
In an effort to make crops grow faster, people use nitrogen in fertilizers. However, the excessive use of those fertilizers in agriculture has had devastating consequences for the environment and human health, as it has contributed to the pollution of groundwater and surface waters. According to the U.S. Environmental Protection Agency (EPA), nutrient pollution caused by excess nitrogen and phosphorus in the air and water, is one of the most widespread, costly and challenging environmental problems.
Just the facts
- Atomic number (number of protons in the nucleus): 7
- Atomic symbol (on the Periodic Table of Elements): N
- Atomic weight (average mass of the atom): 14.0067
- Density: 0.0012506 grams per cubic centimeter
- Phase at room temperature: Gas
- Melting point: minus 321 degrees Fahrenheit (minus 210 degrees Celsius)
- Boiling point: minus 320.42 F (minus 195.79 C)
- Number of isotopes (atoms of the same element with a different number of neutrons): 16 including 2 stable ones
- Most common isotopes: Nitrogen-14 (Abundance: 99.63 percent)
Nitrogen was discovered in 1772 by chemist and physician Daniel Rutherford, when the scientist removed oxygen and carbon dioxide from air, demonstrating that the residual gas would support living organisms or combustion, according to the Los Alamos National Laboratory. Other scientists, including Carl Wilhelm Scheele and Joseph Priestly, were working on the same problem, and called nitrogen "burnt" air, or air without oxygen. In 1786, Antoine Laurent de Lavoisier, called nitrogen "azote," which means "lifeless." This was based on the observation that it is the part of air cannot support life on its own.
- Even though the term "nitrogen" is used in English to refer to the element, Lavoisier's term "azote" is still used in French, and its form is present in "azoto" in Italian or "azot" in Polish.
- Liquid nitrogen is frequently used as a refrigerant, for instance, to store sperm, eggs and other cells used in medical research or fertility clinics, according to the Royal Society of Chemistry.
- Liquid nitrogen is also used to quickly freeze foods and help preserve their flavor, texture, moisture and flavor.
- Nitrogen constitutes 95 percent of the atmosphere of Titan (the largest moon of Saturn), according to the Jet Propulsion Laboratory.
- Nitrogen gas plays a role in the formation of an aurora — a natural display of light in the sky that can be predominantly observed Arctic and Antarctic regions — which occurs when fast-moving electrons from space collide with oxygen and nitrogen in our atmosphere, according to NASA.
- Nitrogen gas can be obtained by heating a water solution of ammonium nitrate (NH4NO3), a crystalline solid that is commonly used in fertilizer.
- About 150 tons of ammonia are produced every year using the Haber process, according to Royal Society of Chemistry.
- Nitrogen in the form of ammonium chloride, NH4Cl, was produced in ancient Egypt by heating a mixture of animal excrement, urine and salt, according to Royal Society of Chemistry.
- Nitroglycerin, a violent explosive used in the production of dynamite, is an oily, colorless liquid that contains nitrogen, oxygen and carbon.
As useful as nitrogen is to humans and other organisms, too much of it can do serious damage to the environment. Plants need nitrogen to grow, but in order to reach their maximum yield, they often need more nitrogen than is normally available to them in the soil, said Randy A. Dahlgren, a professor of soil science at University of California, Davis. To solve this problem in agriculture, people came up with nitrogen-based fertilizers. However, it appears that we have been using more nitrogen than it is environmentally safe. "We put way more fertilizer than we need to on our soils," Dahlgren told Live Science. "Only about 50 percent of the fertilizer nitrogen we put on is actually used by the plants. The other 50 percent is lost." The excess nitrogen can then get into groundwater, he said. In California, for instance, many municipal and private wells have concentrations of nitrate — nitrogen-oxygen chemical units — exceeding the drinking water standard of 10 parts per million, Dahlgren added. Moreover, once nitrogen from fertilizers gets into surface waters such as lakes, it can "feed" algae, leading to harmful algal blooms that make the water carcinogenic, he said.
Another way in which humans contribute to the increasing amount of nitrogen in the environment is through the burning of fossil fuels we produce, he said. "If you drive a car, the exhaust pipe is emitting nitrogen gas," he said, whereas generation in power plants produces nitrogen-type gases called NOx gases (for mono-nitrogen oxides NO and NO2 — nitric oxide and nitrogen dioxide), which in turn are involved in ozone formation and acid rain.
In a study published in October 2010 in the journal Science, researchers outlined how excess use of nitrogen has contributed to the pollution of fresh waters and coastal zones, and may contribute to climate change. At the beginning of the 20th century, human contributions to the natural nitrogen cycle started to increase dramatically, according to the study. "In fact, no phenomenon has probably impacted the nitrogen cycle more than human inputs of nitrogen into the cycle in the last 2.5 billion years," study author Paul Falkowski of Rutgers University said in a statement.
One of the solutions to the issue of excessive nitrogen contributions lies, for instance, in sustainable agriculture, organic farming and raising the awareness of these environmental issues among farmers, Dahlgren said.
"The idea would be to try to eliminate the use of these commercial fertilizers and instead use organic waste," for instance, animal waste, he said. Another step would be to use slow-release fertilizers that have plastic coatings on them and, instead of releasing the nitrogen right away, the release of nitrogen occurs gradually throughout the growing season, "trying to match the nitrogen release from the plastic coated fertilizer with the needs of the plant," he said.
- This website describes what happens when you try to put different objects into liquid nitrogen.
- This infographic illustrates nitrogen pollution in Chesapeake Bay.