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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 9, NUMBER 1, JANUARY 1996

PROFESSIONAL PUBLICATIONS...
OZONE DEPLETION: OZONE DEPLETING SUBSTANCES

Item #d96jan24

"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, 1995.

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.

Item #d96jan25

"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.

Item #d96jan26

"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.

Item #d96jan27

"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.

Item #d96jan28

"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 edition.

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 discussed.