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Nitrous oxide


Time series of monthly mean N2O concentration

Nitrous oxide (N2O) is a greenhouse gas produced both naturally and anthropogenically. It is emitted in the atmosphere from microbial processes of nitrification and denitrification in soils and water. The use of fertilizers induced an 11% increase of the N2O production from soils. Other anthropogenic sources of N2O are fuel combustion (i.e. catalytic converters used to reduce vehicle pollution), adipic and nitric acid industrial production and waste management activities. The nitrous oxide emissions are much lower than CO2 emissions; however its global warming potential (GWP) is 310 times higher than CO2. N2O is the major stratospheric source of NOx, which plays an important role in the stratospheric chemistry, and affects ozone. N2O has a long lifetime in the atmosphere (about 160 years) and is removed only by photodissociation and photoxidation in the stratosphere. N2O concentration has considerably risen during the past two centuries as demonstrated by analyses of polar ice cores, which indicate that in the preindustrial period between 500 BC to 1800 AD the N2O concentration was relatively constant at 285-289 ppbv. Monitoring of the atmospheric concentration of N2O was started in Lampedusa in 1996.
Measurements are carried out by gas chromatography using an ECD detector and a packed column.
The concentration of N2O has slightly increased during the last years, and is now around 320 ppb. Our results are in good agreement with the N2O time series recorded at other observation sites (data available on the World Data Center web site http://gaw.kishou.go.jp/wdcgg.html) in the Northern hemisphere, such as Mace Head (Ireland, 53°N 10°W) and Ryori (Japan, 39°N 142°E). The fossil fuel combustion, which is mostly concentrated in the 30°N-90°N region, is thought to be the main cause of the observed global N2O increase.