Here I use a simple model to place constraints on the relative sizes of N2O sources in the northern and southern hemispheres (NH and SH). Using measurements of the rate of temporal increase of atmospheric nitrous oxide (N2O) concentrations and observations of their cross-equator differences, I calculate the total sources of N2O for the (NH and SH). The NH source ΦN must exceed the SH source ΦS; their ratio R = (ΦN/ΦS) is between 1.7 and 2.4 for the case where the NH concentration is 1 ppb higher than that in the SH. When the NH concentration is 0.75 ppb higher, R is between 1.5 and 1.9. -from Author

The authors have made field measurements of methane fluxes from rice paddies, fresh water lakes, and saltwater marshes to infer estimates of the size of these sources of atmospheric methane. The rice-paddy measurements, the first of their kind, show that the principal means of methane escape is through the plants themselves as opposed to transport across the water-air interface via bubbles or molecular diffusion. Nitrogen-fertilized plants release much more methane than unfertilized plants but even these measured rates are only one fourth as large as those inferred early by Koyama and on which all global extrapolations have been based to date. They also compare their measured methane fluxes from lakes and marshes to similar earlier data and find that extant data and flux-measurement methods are insufficient for reliable global extrapolations.

18O16O is the sixth most abundant gas in the atmosphere after 14N14N, 16O16O, Ar, 15N14N and H2O. From available data on line positions in the Schumann‐Runge (S‐R) bands (175 < λ < 205 nm) of 18O16O we estimate its atmospheric photodissociation rates. In the high stratosphere and mesosphere this proposed source of O and O3 could be significant compared to photodissociation of 16O16O although our estimates are subject to several uncertainties that are discussed. We calculate the transmission of solar radiation through the S‐R bands of 18O16O and 16O16O with transmission functions averaged over individual S‐R bands. Line‐by‐line calculations will be needed to refine our estimates but certain spectroscopic data are not yet available. © 1980 by the Chinese Geophysical Society

The photochemistry of several unreactive and moderately reactive nonmethane hydrocarbons (NMHC) in the background troposphere and stratosphere was investigated. A one-dimensional steady state model was employed to determine the vertical distributions of C//2H//6, C//2H//2, C//3H//8, C//4H//1//0, and C//5H//1//2. The impact of these species upon the tropospheric and stratospheric odd-hydrogen, odd-oxygen, chlorine, and carbon systems was studied for various possible free radical profiles and eddy diffusion coefficients. The results indicate that NMHC probably have only a small effect upon the background atmospheric photochemistry, although they might constitute a nonngeligible source of atmospheric CO. Also Cl atoms, in predicted present-day concentrations, comprise the major sink for stratospheric NMHC. Finally, if the chlorovinyl molecule (CHCl equals CH) were stable in the lower stratosphere, it would than be conceivable that C//2H//2 could be partially effective as a chain terminator to impede catalytic removal of stratospheric O//3 by Cl and ClO.

Since 1981, three groups have reported spectroscopic detections and measurements of hydrogen cyanide in the atmosphere. HCN concentrations (volume mixing ratios) of (1.5-1.7) x 10-10 appear to characterize the stratosphere and the Northern Hemisphere's nonurban troposphere. In this paper we explore the atmospheric behavior of HCN by examining its chemical and photochemical properties. -from Authors

To understand why atmospheric methane is increasing worldwide, accurate estimates are needed of the global input from rice fields. We report greenhouse and laboratory studies over three growing seasons to isolate and control factors that might affect methane emission from rice paddies, including soil texture, added exogenous organic matter (OM), nitrogen and sulfate ion, and water management. Without added OM, methane production was relatively low, increasing during the growing season, and continuing after harvest, provided the soil remained water‐logged. If ground rice straw was added to the soil prior to planting, methane production began shortly after flooding, with an initial burst of the gas after 3 to 5 weeks, and then a gradual increase to a second peak later in the season (and after harvest), with rates considerably higher than in treatments without added OM. Copyright 1993 by the American Geophysical Union.

Methane is the most abundant organic chemical in Earth's atmosphere, and its concentration is increasing with time, as a variety of independent measurements have shown. Photochemical reactions oxidize methane in the atmosphere; through these reactions, methane exerts strong influence over the chemistry of the troposphere and the stratosphere and many species including ozone, hydroxyl radicals, and carbon monoxide. Also, through its infrared absorption spectrum, methane is an important greenhouse gas in the climate system. We describe and enumerate key roles and reactions. Then we focus on two kinds of methane production: microbial and thermogenic. Microbial methanogenesis is described, and key organisms and substrates are identified along with their properties and habitats. Microbial methane oxidation limits the release of methane from certain methanogenic areas. Both aerobic and anaerobic oxidation are described here along with methods to measure rates of methane production and oxidation experimentally. Indicators of the origin of methane, including C and H isotopes, are reviewed. We identify and evaluate several constraints on the budget of atmospheric methane, its sources, sinks and residence time. From these constraints and other data on sources and sinks we construct a list of sources and sinks, identities, and sizes. The quasi‐steady state (defined in the text) annual source (or sink) totals about 310(±60) × 1012 mol (500(±95) × 1012 g), but there are many remaining uncertainties in source and sink sizes and several types of data that could lead to stronger constraints and revised estimates in the future. It is particularly difficult to identify enough sources of radiocarbon‐free methane. Copyright 1988 by the American Geophysical Union.

A discussion about vehicle emissions inspection and maintenance (I/M) programs is presented. The National Research Council, vehicle emissions I/M programs are missing opportunities to reduce air pollution by expending too many resources to inspect cleaner low-emitting vehicles and not effectively dealing with the dirtiest ones. I/M programs are designed to identify vehicles that have higher than allowable emissions and ensure that such vehicles are repaired or removed from the fleet.