Nitrous Oxide | Research & Encyclopedia Articles

Nitrous oxide (N₂O), also called di-nitrogen monoxide, is one of several gaseous oxides of nitrogen. It is sometimes referred to as laughing gas, because when inhaled it causes a feeling of intoxication, mild hysteria, and sometimes laughter. The gas is colorless and has a faint odor and slightly sweet taste. It can lessen the sensation of pain and is used as an anesthetic in dentistry and in minor surgery of short duration. For more complex surgery, it is combined with other anesthetics to produce a deeper and longer-lasting state of anesthesia. Nitrous oxide also is commonly used as a propellant for pressurized food products, and sometimes is used in race cars to boost the power of high performance engines. It is one of the few gases capable of supporting combustion. In this process, it transfers its oxygen to the material being combusted and is converted to molecular nitrogen (N₂).

Nitrous oxide is an important component of the Earth's upper atmosphere at heights above 30 mi (45 km). It is one of the greenhouse gases, together with carbon dioxide, methane, and ozone, that allow radiation from the Sun to reach the Earth's surface but prevent the infrared or heat component of sunlight from re-irradiating into space. This leads to the so-called greenhouse effect, and results in warmer temperatures at the earth's surface. Greenhouse warming is important in creating surface temperatures suitable for life, but recent studies have shown that the levels of some greenhouse gases are increasing at rates that are a cause for concern. Human-made gases, such as chlorofluorocarbons, are also contributing to the greenhouse effect. An increase in the Earth's ability to trap infrared radiation can be expected to result in global climate change with wide-ranging consequences.

Concern over greenhouse gases has centered on reports of increasing concentrations of atmospheric carbon dioxide (CO₂). Two factors thought to be responsible are the widespread use of fossil fuels (which add CO₂ to the atmosphere) and the rapid destruction of tropical rain forests which remove CO₂). The levels of other greenhouse gases may also be changing. Studies indicate that atmospheric levels of nitrous oxide may also be increasing as a result of human activity. Nitrous oxide is produced in nature by microorganisms acting on nitrogen-containing compounds in the soil. Increased use of nitrogen fertilizer in lawns, gardens, and agricultural fields may stimulate microbial production of nitrous oxide. Manure and municipal sludge, applied as soil enhancers and fertilizers, and burning fossil fuels also may contribute to an increase.

Nitrous oxide production in soils is greatly influenced by soil temperature, moisture level, organic content, soil type, pH, and oxygen availability. In agricultural soil, rates of fertilizer application, fertilizer type, tillage practices, crop type, and irrigation all influence nitrous oxide production. High soil temperature, moisture, and organic content tend to enhance production, whereas tilling of the soil tends to lower it. The relative importance of each of these factors has not been determined, and further study is needed to develop recommendations to limit harmful nitrous oxide emissions from soils.

Minnesota Pollution Control Agency, Air Quality Division. Minnesota Greenhouse Gas Inventory 1990. St. Paul, MN: Minnesota Pollution Control Agency, 1995.

Umarov, M. "Biotic Sources of Nitrous Oxide (N₂O) in the Context of Global Budgets of Nitrous Oxide," Soils and the Greenhouse Effect, A. Bowman, ed. Chicester, U.K.: John Wiley and Sons, 1990.

Smith, S.C. "N₂O Laughing Gas: Has the NHRA Been Looking the Other Way after Allegations That Pro Stock Champions Got There with the Help of Nitrous Oxide?" Car and Driver 41, no. B (February 1996): 105.

U.S. Department of Energy. Emissions of Greenhouse Gases in the United States, 1985–1990. DOE/EIA-0573. Washington, D.C.: GPO, 1993.

U.S. Environmental Protection Agency. State Workbook: Methodologies for Estimating Greenhouse Gas Emissions. EPA-230-B-92-002, Washington, D.C.: GPO, 1992.

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