February 28, 2007
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A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 9, NUMBER 1, JANUARY 1996
OZONE DEPLETION: OZONE DEPLETING SUBSTANCES
"Rapid Degradation of Atmospheric Methyl Bromide in Soils,"
J.H. Shorter, C.E. Kolb (Ctr. Chem. & Environ. Phys., Aerodyne Res. Inc.,
Billerica MA 01821) et al., Nature, 377(6551), 717-719, Oct. 26,
Methyl bromide, widely used as an agricultural fumigant, is considered an
important contributor to ozone depletion. Laboratory and field experiments
reported here show that soil bacteria can consume large quantities of the gas.
This finding suggests an atmospheric lifetime for methyl bromide of about 0.8
years, half the previous best estimate, and an ozone depletion potential about
30% less than the previous estimate.
"Methyl Bromide Diffusion and Emission Through Soil Columns Under
Various Management Techniques," Y. Jin (Dept. Soil & Environ. Sci.,
Univ. California, Riverside CA 92521), W.A. Jury, J. Environ. Qual.,
24(5), 1002-1009, Sep.-Oct. 1995.
About 80% of anthropogenic methyl bromide is used as a soil fumigant, so the
factors determining its escape to the atmosphere under various agricultural
practices are of interest. Experiments described here show that polyethylene
films were only marginally effective in preventing emission from treated soil,
but irrigation prior to covering the soil with film was much more effective.
"Measurements of HCFC-142b and HCFC-141b in the Cape Grim Air
Archive: 1978-1993," D.E. Oram (Sch. Environ. Sci., Univ. E. Anglia,
Norwich NR4 7TJ, UK), C.E. Reeves et al., Geophys. Res. Lett., 22(20),
2741-2744, Oct. 15, 1995.
The growth of atmospheric concentrations of these hydrochlorofluorocarbons,
popular interim substitutes for CFCs, was determined from stored air samples
collected since 1978. Both species show rapid growth after 1990. A 2-D global
atmospheric chemistry model used to estimate global emissions based on these
data suggests that emission estimates of the AFEAS (Alternative Fluorocarbons
Environmental Acceptability Study) may be low by a factor between 1.5 and 2.2.
"Observed Stratospheric Profiles and Stratospheric Lifetimes of
HCFC-141b and HCFC-142b," J.M. Lee (ASP, NCAR, POB 3000, Boulder CO 80307),
W.T. Sturges et al., ibid., 22(11), 1369-1372, June 1, 1995.
Presents the first stratospheric profile measurements of these two interim
CFC substitutes. Derives a stratospheric lifetime of 68 years for HCFC-141b and
an estimated minimum stratospheric lifetime for HCFC-142b of 138 years (assuming
an N2O lifetime of 110 years). Neither compound is now in equilibrium in the
stratosphere, due to rapidly increasing emissions.
"Ozone Influence Index of Ozone-Active Gases in the Present-Day
Global Atmosphere," I.L. Karol (Main Geophys. Observatory, Russia), A.A.
Kiselev, Russian Meteor. & Hydrol., No. 6, 22-26, 1994. English
Introduces the concept of ozone influence index (OII), the degree of
influence on ozone depletion of an atmospheric constituent, and compares it to
the widely accepted concept of ozone depletion potential. OII values are
computed for methane, some CFCs, and halons. Limits of the concept are
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