Atmospheric methyl bromide: Trends and global mass balance
- Oregon Graduate Inst., Beaverton (United States)
Atmospheric methyl bromide is of considerable environmental importance as the largest reservoir of gaseous bromine in the atmosphere. Bromine gases can catalytically destroy stratospheric ozone. Since agricultural activities, automobiles, biomass burning, and other human activities produce CH[sub 3]Br, it is of interest to know its global mass balance and particularly the specific sources and sinks. In this paper the authors provide a decadal time series of global CH[sub 3]Br concentrations in the Earth's atmosphere. The data show that average concentrations are about 10 pptv and during the last 4 years may be increasing at 0.3 [plus minus] 0.1 pptv/yr (3%/yr [plus minus] 1%/yr). They estimate that the atmospheric lifetime of CH[sub 3]Br that is due to reaction with OH, is about 2 years, resulting in a calculated global emission rate of about 100 Gy/yr. Ocean supersaturations of 140-180% are observed, and atmospheric concentrations over the open oceans are higher than at comparably located coastal sites. The ocean source is estimated to be about 35 Gg/yr. The remaining emissions must come from other natural sources and anthropogenic activities. The results are based on some 2,200 samples obtained over more than a decade. Mass balance calculations explain most aspects of the present data but other implications are not easily reconciled, leaving open the possibility of undiscovered sources and sinks. 20 refs., 5 figs., 4 tabs.
- OSTI ID:
- 6720892
- Journal Information:
- Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 98:D2; ISSN 0148-0227; ISSN JGREA2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
540120* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (1990-)
AUTOMOBILES
BIOMASS
BROMINATED ALIPHATIC HYDROCARBONS
BROMINE
CATALYSIS
CATALYSTS
EARTH ATMOSPHERE
ECOLOGICAL CONCENTRATION
ELEMENTS
EMISSION
ENERGY SOURCES
FLUIDS
GASES
GLOBAL ASPECTS
HALOGENATED ALIPHATIC HYDROCARBONS
HALOGENS
LIFETIME
MASS BALANCE
METHYL BROMIDE
NONMETALS
ORGANIC BROMINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OZONE
RENEWABLE ENERGY SOURCES
SINKS
VEHICLES