Nitrous oxides atmospheric concentration

Figure 16.10 (A) Nitrous oxide (N2O) concentrations and isotopic composition for water samples collected at Station ALOHA. [Left] Depth profile of N2O showing a distinct mid-depth maximum of 60 nM coincident with the dissolved oxygen minimum. [Center] N isotope composition of N2O. [Right] 0 isotope composition of N2O. Data from Dore et al. (1998) and B. Popp and J. Dore (unpublished). (B) N2O saturation state, expressed as a percentage of air saturation, for the upper portion of the water column at Station ALOHA during the period September 1992— September 1994. The vertical dashed line indicates equilibrium (100% saturation) with atmospheric N2O. With the exception of one measured value on cruise HOT-45, all determinations indicate significant N2O saturation relative to the atmosphere which implies both a local source and a net ocean-to-air gas flux.From Dore and Karl (1996a).

Machida, T., Nakazawa, T., Fujji, Y. et al. (1995). Increase in atmospheric nitrous oxide concentration during the last 250 years. Geophys. Res. Lett. 22, 2921-2924. 

Problems may arise when the atmospheric concentration of greenhouse gases increases. Since the beginning of the industrial revolution, atmospheric concentrations of carbon dioxide have increased nearly 30%, methane concentrations have more than doubled, and nitrous oxide concentrations have risen by about 15%. These increases have enhanced the heat-trapping capability of the earth s atmosphere. 

Atmospheric concentrations of (a) carbon methane, and (c) nitrous oxide over the past... 

It is thought that little net NO is produced in denitrification, it being readily reduced to N2O, and nitrification is therefore the main source of NO (Anderson and Levine, 1986 Skiba et al, 1993). Nitrous oxide is also produced in both nitrification and denitrification. At low O2 concentrations in otherwise aerobic soil, small amounts of N2O are formed as a by-product of nitrification, N2O not itself being reduced to NO,. In denitrification, the proportion of N2O produced relative to N2 increases as the availability of O2 increases and that of carbon decreases (Tiedje, 1988). In general only a small fraction of the N nitrified or denitrified in these pathways is released as NO or N2O. The emission is therefore sensitive to the amount of mineral N in the system, which is driven principally by additions of nitrogen fertilizers and deposition of nitrogen from the atmosphere. 

Xenon is an odourless, colourless, non-explosive gas present in the atmospheres of both Earth and Mars in concentrations of approximately 0.08 ppm. Its density is approximately three times and its viscosity twice that of nitrous oxide. Like other noble gases, such as helium and argon, its outer electron shell contains the maximum number of electrons (8) making the molecule highly stable chemically. Despite this, its anaesthetic activity indicates that xenon binds to cell proteins and cell membrane constituents. 

Since nitrous oxide is one of the most soluble inorganic gases in the polymer solid, under our experimental conditions nitrous oxide can be regarded not only as an atmosphere but as a small additive in the polymer solid. In the polymer solid, especially in its amorphous region, nitrous oxide apparently dissolves homogeneously and disperses molec-ularly. At 600 mm. of Hg, in the case of polyethylene, the weight concentration is calculated as 0.1 to 0.2%. The gas solubility in poly-... 

The concentration of nitrous oxide (N20) in the atmosphere is only about 0.30 ppm but it increases by about 0.2% per year and so is at least partly of anthropogenic origin. Nitrous oxide is a product of the degradation of nitrate fertilizers, but some 7 x 105 tonnes of N2O are released annually to the atmosphere during production of nylon.20 The residence time of N20 in the atmosphere is about 150 years, and it could in the future contribute up to 10% of the anticipated greenhouse warming. 

The concentration of nitrous oxide (N2O) in the atmosphere is increasing. This is a concern, since N2O has been identified as a greenhouse gas and as a source of ozoneconsuming NO in the stratosphere. A significant source of N2O to the atmosphere is production of adipic acid (AA), which is used in the production of nylon. Adipic acid is formed from reaction of cyclohexanol with nitric acid (HNO3) according to the scheme in Fig. 13.13. 

The global atmospheric nitrous oxide concentration increased from a preindustrial value of about 270 ppb to 319 ppb in 2005. The growth rate has been approximately constant since 1980 and more than 30% of all nitrous oxide emissions are primarily due to agriculture. 

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