February 28, 2007
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FROM VOLUME 5, NUMBER 9, SEPTEMBER 1992
CHEMICAL CYCLES: METHANE
"Interannual Variations in Tundra Methane Emission: A Four-Year Time Series at Fixed Sites," S.C. Whalen (Inst. Marine Sci., Univ. Alaska, Fairbanks AK 99775), W.S. Reeburgh, Global Biogeochem. Cycles, 6(2), 139-160, June 1992.
Summarizes weekly net CH4 flux measurements at permanent sites representing important plant components of the Arctic tundra. The data coincide with variations in precipitation and temperature of interest in regional and global modeling, and are useful for setting bounds on the role of tundra in global change. Arctic wet meadow and tussock/shrub tundra presently emit an estimated 42 ñ 26 Tg CH4 yr-1.
"Future CH4 Emissions from Rice Production," C. Anastasi (Dept. Chem., Univ. York, Heslington, York YO1 5DD, UK), M. Dowding, V.J. Simpson, J. Geophys. Res., 97(D7), 7521-7525, May 20, 1992.
Emissions to the year 2025 were calculated using a model based on population predictions and on current values of per capita rice production for the 94 major rice-producing countries. Emissions are predicted to increase by an average of 1.1% yr-1 from the 1990 level, to 145 Tg yr-1 in 2025.
"Consumption of Atmospheric Methane by Desert Soils," R.G. Striegl (USGS, Box 25046, MS 413, Denver CO 80225), T.A. McConnaughey et al., Nature, 357(6374), 145-147, May 14, 1992.
Deserts, which constitute 20% of total land surface, are not currently included in estimates of global soil methane uptake. Measurements described here show uptake rates as great as 4.38 mg CH4 m-2 d-1. The global CH4 sink term needs to be increased by about 7 x 1012 g yr-1 to account for the contribution of desert soils.
"Northern Fens: Methane Flux and Climatic Change," N. Roulet (Dept. Geog., York Univ., North York, Ont. M3J 1P3, Can.), T. Moore et al., Tellus, 44B(2), 100-105, Apr. 1992.
Water table and ground temperature responses of peat fens to a doubled CO2 scenario were calculated, and applied to observed relationships among methane flux, water table and ground temperature. Results suggest that methane emissions from northern peatlands will be more sensitive to changes in moisture than to changes in temperature.
"Variations in Atmospheric Methane at Mauna Loa Observatory Related to Long-Range Transport," J.M. Harris (CMDL, 325 Broadway, Boulder CO 80303), P.P. Tans et al., J. Geophys. Res., 97(D5), 6003-6010, Apr. 20, 1992.
Methane measurements, radon measurements and air mass trajectories were examined to determine relationships among methane source/sink regions, flow patterns at Mauna Loa, and methane variations on the synoptic to seasonal scale. Changes in flow pattern from sink to source origins can result in a 50 ppbv rise in methane mixing ratio over a few days, especially in winter.
"Impact of Recent Total Ozone Changes on Tropospheric Ozone Photodissociation, Hydroxyl Radicals, and Methane Trends," S. Madronich (NCAR, POB 3000, Boulder CO 80307), C. Granier, Geophys. Res. Lett., 19(5), 465-467, Mar. 3, 1992.
Trends in total ozone from 1979-1989 were analyzed to derive the corresponding change in the tropospheric photodissociation constant for the first step in the production of the hydroxyl radical. Changes in hydroxyl due to these trends may have contributed to the slowing of atmospheric methane increases observed recently.
"Emission and Production of Methane in the Paddy Fields of Japan," K. Yagi (Nat. Inst. Agroenviron. Sci., Ibaraki 305, Japan), K. Minami, Japan Agric. Res. Quart., 25(3), 165-171, Dec. 1991.
Measurements show strong seasonal CH4 variations, depending on soil Eh, water management and mineral fertilizer applied. Seasonal variations of emission are mainly caused by variation in CH4 production, but the ratio of production to emission varies among soils, suggesting that physical and chemical properties of soils may be significant.
"Agronomic Aspects of Wetland Rice Cultivation and Associated Methane Emissions," A.F. Bouwman (Rijksinst. Volksgezondheid Milieuhyg., LAE, POB 1, 3720 BA Bilthoven, Neth.), Biogeochem., 15(2), 65-68, 1991.
Reviews factors affecting CH4 emissions from rice cultivation, such as mineral fertilizers, added organic matter and water management. Reduction of global emissions seems difficult; research is required on interactions between soil chemical and soil physical properties, and on soil, water and crop methanogenesis.
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