Nitrous oxide (N2O) is a greenhouse gas included in the Kyoto Protocol. Its production from excited ozone (O3) may potentially influence inverse modeling, future growth projection, and the use of ...mass‐independent Δ17O anomaly of N2O for probing paleoatmospheric O3. On the basis of the three‐component model of N2O quantum yield in photolysis of O3 in air, the globally averaged atmospheric production of N2O from O3 electronically excited by the Hartley‐Huggins band and from highly vibrationally excited ground‐state O3 are 1.01 and 0.26 Tg N a−1, respectively. The sum of the two productions is 9.4 and 7.7%, respectively, of the N2O from microbial and anthropogenic activities estimated by Global Emissions Inventory Activity and by the Intergovernmental Panel on Climate Change (2001). Uncertainties in these results are discussed. Subject to those uncertainties, inverse modeling of N2O that neglects productions from O3 could yield artificially magnified (by about 7%) globally averaged emission of N2O from microbial and anthropogenic activity and introduce distortion in the regional and seasonal pattern in that emission. Experiments that could narrow the uncertainties are discussed. Production from highly vibrationally excited O3 reduces the steepness in the decrease of N2O volume‐mixing ratios (VMR) above 35 km. Modeled and observed VMR comparisons show latitude‐ and season‐dependent overestimation and underestimation of the N2O VMR by models. Globally averaged comparison suggests possible N2O source deficit in the stratosphere. Limitations, uncertainties, and need for experiments associated with this possibility are also discussed. If proven real, the possible missing N2O source could influence the atmospheric affects of solar UV variability, subject to conditions that are discussed.
Isotopic ($\delta^{17}$O and $\delta^{18}$O) measurements of stratospheric and mesospheric carbon dioxide (CO$_2$) and oxygen (O$_2$), along with trace species concentrations (N$_2$O, CO, and ...CO$_2$), were made in samples collected from a rocket-borne cryogenic whole air sampler. A large mass-independent isotopic anomaly was observed in CO$_2$, which may in part derive from photochemical coupling to ozone (O$_3$). The data also require an additional isotopic fractionation process, which is presently unidentified. Mesospheric O$_2$ isotope ratios differed from those in the troposphere and stratosphere. The cause of this isotopic variation in O$_2$ is presently unknown. The inability to account for these observations represents a fundamental gap in the understanding of the O$_2$ chemistry in the stratosphere and mesosphere.
The present study examines the effects of atmospheric production of NOX directly from the O2 and N2 principals via the reaction of O2(B3Σ) with N2 and a second process provisionally theorized as ...absorption of a photon with 190 ≤ λ ≤ 204 nm by O2•N2 collision complex. The NOX production from O2(B3Σ) is ∼12% of the production from the “classical” O(1D) + N2O reaction in the region of their maxima in altitude. The diurnally averaged vmr (volume mixing ratios) of both NOX and NOY are enhanced similarly by 10 to 15% at the most. The NOX/NOY ratio is therefore unaffected. The production of NOX from O2(B 3Σ) compensates for the decrease in the classical production due to the recently discovered faster quenching of O(1D) by N2. In the O2‐poor ancient atmosphere, when the solar UV in the Schumann‐Runge bands penetrated much deeper into the denser lower atmosphere, the contribution of the NOX production from O2(B3Σ) may have been more pronounced than in the O2‐rich present atmosphere. Below 22 km, NOX production from the second process far exceeds the classical production. Such a production would almost certainly lead to NOX and NOY vmr exceeding their observed values and would call for an extensive rethinking of the atmospheric NOX budget. Because these implications of the two new NOX sources are quite serious, attention has been drawn to many, equally serious, open issues at the levels of both laboratory experiments and basic quantal processes that require further studies.
Laboratory studies show that the reaction of short-lived O.sub.2(B.sub.3Sigma.sub.u molecules (lifetime ~ 10 picoseconds) with N.sub.2 and the photodissociation of the N.sub.2:O.sub.2 dimer produce ...NO.sub.x in the stratosphere at a rate comparable to the oxidation of N.sub.2.O by O(D.sup.1). This finding implies; the existence of unidentified NO.sub.x, sinks in the stratosphere. The NO.sub.2 observed in this experiment is isotopically heavy with a large N.sub.15/N.sup.14 enhancement. However, photo-dissociation of this NO.sub.2 unexpectedly produced NO molecules with a low N.sup.15/N.sup.14 ratio. The diurnal odd-nitrogen cycle in the stratosphere will be marked by a complex isotope signature that will be imprinted on the halogen and HO.sub.x catalytic cycles.
The present study examines the effects of atmospheric production of NO
X
directly from the O
2
and N
2
principals via the reaction of O
2
(B
3
Σ) with N
2
and a second process provisionally theorized ...as absorption of a photon with 190 ≤ λ ≤ 204 nm by O
2
•N
2
collision complex. The NO
X
production from O
2
(B
3
Σ) is ∼12% of the production from the “classical” O(
1
D) + N
2
O reaction in the region of their maxima in altitude. The diurnally averaged vmr (volume mixing ratios) of both NO
X
and NO
Y
are enhanced similarly by 10 to 15% at the most. The NO
X
/NO
Y
ratio is therefore unaffected. The production of NO
X
from O
2
(B
3
Σ) compensates for the decrease in the classical production due to the recently discovered faster quenching of O(
1
D) by N
2
. In the O
2
‐poor ancient atmosphere, when the solar UV in the Schumann‐Runge bands penetrated much deeper into the denser lower atmosphere, the contribution of the NO
X
production from O
2
(B
3
Σ) may have been more pronounced than in the O
2
‐rich present atmosphere. Below 22 km, NO
X
production from the second process far exceeds the classical production. Such a production would almost certainly lead to NO
X
and NO
Y
vmr exceeding their observed values and would call for an extensive rethinking of the atmospheric NO
X
budget. Because these implications of the two new NO
X
sources are quite serious, attention has been drawn to many, equally serious, open issues at the levels of both laboratory experiments and basic quantal processes that require further studies.
Laboratory studies show that the reaction of short-lived O2(B3Sigmau) molecules (lifetime approximately 10 picoseconds) with N2 and the photodissociation of the N2:O2 dimer produce NOx in the ...stratosphere at a rate comparable to the oxidation of N2O by O(1D). This finding implies the existence of unidentified NOX sinks in the stratosphere. The NO2 observed in this experiment is isotopically heavy with a large 15N/14N enhancement. However, photodissociation of this NO2 unexpectedly produced NO molecules with a low 15N/14N ratio. The diurnal odd-nitrogen cycle in the stratosphere will be marked by a complex isotope signature that will be imprinted on the halogen and HOX catalytic cycles.
Laboratory studies show that the reaction of short-lived O$_2$(B$^3\Sigma_u$) molecules (lifetime ∼10 picoseconds) with N$_2$ and the photodissociation of the N$_2$:O$_2$ dimer produce NO$_x$ in the ...stratosphere at a rate comparable to the oxidation of N$_2$O by O($^1$D). This finding implies the existence of unidentified NO$_x$ sinks in the stratosphere. The NO$_2$ observed in this experiment is isotopically heavy with a large $^{15}$N/$^{14}$N enhancement. However, photo-dissociation of this NO$_2$ unexpectedly produced NO molecules with a low $^{15}$N/$^{14}$N ratio. The diurnal odd-nitrogen cycle in the stratosphere will be marked by a complex isotope signature that will be imprinted on the halogen and HO$_x$ catalytic cycles.
Importance of this paper: We report a new development of importance to all those who, for the sake of the global environment, care about the origin and evolution of atmospheric greenhouse gases. In ...an easy-to-read style, we have collected evidences converging on the significant atmospheric production of nitrous oxide from extremely highly-excited ozone. This production implies that the current IPCC methodology may be overestimating nitrous oxide emission from biogenic and anthropogenic activities and/or there are missing sinks. These implications need attention since nitrous oxide is a greenhouse gas with a rising atmospheric loading and an understanding of its sources and sinks is essential for making sound regulatory policy.
Today our understanding of the sources and sinks of nitrous oxide (N2O) may be at a turning point. Currently, it is believed that there are no atmospheric photochemical sources of N2O and that microbial activity at the earth's surface (soil, lake, ocean, etc.) is the major source of atmospheric N2O. Anthropogenic activities are thought to release N2O into the atmosphere, but their magnitude is uncertain and probably minor. Here we present estimates of atmospheric production of N2O from excited ozone (O3) based on comprehensive laboratory experiments. These experiments covered a large range of pressures from 1 to 1000 torr to distinguish between the various possibilities on the basis of their pressure dependencies, and used two reaction vessels of widely varying surface-to-volume ratios to distinguish between surface and gas phase reactions. Never before in the history of the experimental studies of N2O under atmospherically significant conditions has such a comprehensive coverage of the parameter space been attempted. From this data, the atmospheric production is substantial, being around 40% of its “classical” source strength. In order to put the atmospheric production in proper perspective, we also present those considerations that led us to look into the atmospheric sources. If we accept the IPCC’s 1990 position on the N2O source-sink inventory, then the atmospheric production of N2O bridges the source deficits. On the other hand, if the later IPCC positions of a nearly balanced inventory is accepted, then the new source means that either the post-1990 IPCC methodology for establishing national inventories of greenhouse gas emissions overestimates N2O emissions or there exists some hitherto unrecognized sinks of N2O.
Laboratory studies show that the reaction of short-lived O sub(2)( super(3) capital sigma sub(u)) molecules (lifetime similar to 10 picoseconds) with N sub(2) and the photodissociation of the N ...sub(2):O sub(2) dimer produce NO sub(x) in the stratosphere at a rate comparable to the oxidation of N sub(2)O by O( super(1)D). This finding implies the existence of unidentified NO sub(x) sinks in the stratosphere. The NO sub(2) observed in this experiment is isotopically heavy with a large super(15)N/ super(14)N enhancement. However, photodissociation of this NO sub(2) unexpectedly produced NO molecules with a low super(15)N/ super(14)N ratio. The diurnal odd-nitrogen cycle in the stratosphere will be marked by a complex isotope signature that will be imprinted on the halogen and HO sub(x) catalytic cycles.
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