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Showing papers on "Atmospheric methane published in 1978"


Journal ArticleDOI
TL;DR: In this article, the methane cycle of an artificially eutrophic shield lake is considered by relating in situ rates of production to rates of oxidation and evasion, and it is shown that methane production was important in regenerating carbon from sediments.
Abstract: The methane cycle of an artificially eutrophic shield lake is considered by relating in situ rates of production to rates of oxidation and evasion. Methane production rates f’or oxygenated and anoxic sediments were quite consistant throughout the year, ranging from ~1.0 to ~10 mmol m−2 sediment d−1. Methane oxidation rates were highly variable (0.02–32 mmol m−2 lake surface d−1) as were evasion rates (0.0–60 mmol m−2 lake surface d−1). Oxidation and evasion rates both peaked during fall overturn and were very low during the remainder of the year. Methane production was important in regenerating carbon from sediments. Fifty-five percent of total carbon input was regenerated as methane during 1 year and 36% of this total carbon input was recycled by methane oxidation. Methane oxidation was not an important source of carbon dioxide for primary producers or of seston for secondary grazers during the summer. During some winters production of particulate carbon by methane oxidizers may have been an important source of seston for grazers. Methane oxidation was the most important contributor to the development of total lake anoxia under ice cover.

289 citations


Journal ArticleDOI
TL;DR: In this article, the average mixing ratio of methane in the troposphere was 1.41 ppm and 1.3 ppmv for the northern and southern hemisphere, respectively, which corresponds to a total amount of 4×1015 g of CH4 present in the atmosphere.
Abstract: In 1972 average mixing ratio of methane in the troposphere was 1.41 ppm and 1.3 ppmv for the northern and southern hemisphere, respectively, which corresponds to a total amount of 4×1015 g of CH4 present in the atmosphere. Most is of recent biologic origin.14C analyses show that no more than 20 percent is released by fossil sources. The various ecosystems producing CH4 are discussed and the total annual production is estimated to lie between 5.5×1014 g/yr and 11×1014 g/yr. The corresponding turnover times for atmospheric CH4 range from 4 to 7 yrs. The destruction of CH4 takes place mainly in the troposphere, most probably through the reaction of CH4 + OH ↠ CH3 + H2O. About 10 percent of the CH4 is destroyed in the stratosphere. The CH4 cycle contributes on the order of 1 percent to the atmospheric carbon cycle.

227 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that both methane and oxygen are rapidly consumed in “young” water but, while oxygen consumption continues at a low rate throughout the deep ocean, methane consumption virtually ceases within about 100 years of isolation from the surface ocean.
Abstract: Oceanic dissolved methane concentrations are normally in excess of atmospheric equilibrium values in surface waters but show a rapid decrease with depth. Deep North Atlantic waters have only ca. 30% of their atmospheric equilibrium values of methane and deep North Pacific waters have only ca. 10%. Methane consumption rates calculated from methane analyses and water mass ages derived from published data on SII/3He ages, r4C ages, and model calculations show that both methane and oxygen are rapidly consumed in “young” water but, while oxygen consumption continues at a low rate throughout the deep ocean, methane consumption virtually ceases within about 100 years of isolation from the surface ocean.

105 citations



01 Jan 1978
TL;DR: In this paper, photochemical model calculations indicate that significant perturbations in tropospheric ozone, CH4, and related compounds may occur in the coming decades due to increased anthropogenic emissions of CO and NO(x).
Abstract: Photochemical model calculations indicate that significant perturbations in tropospheric OH, CH4, and related compounds may occur in the coming decades due to increased anthropogenic emissions of CO and NO(x). The magnitude and direction of the perturbation depends on future emission rates of CO and NO(x) and also on the efficiency with which urban NO(x) is transported to the ambient atmosphere. If CO and NO(x) emissions increase at comparable rates, the CO effect on OH will dominate and OH will decrease while CH4 increases. The effects of a variation in tropospheric OH, halocarbons, and other compounds include a perturbation to stratospheric ozone and the atmosphere's thermal equilibrium.

1 citations