IsoPrime稳定同位素质谱仪测空气中甲基溴的稳定同位素组

Methyl bromide (CH3Br) constitutes the largest source
of bromine atoms to the stratosphere and plays an important
role in stratospheric ozone depletion. However, the CH3Br
atmospheric budget remains uncertain. We report the first
measurements of stable carbon isotope ratios for
atmospheric CH3Br and explore the constraints they
provide for the atmospheric budget. The measured d13C
of CH3Br ranged from 44.8% to 41.2% (mean value
43.1%, N = 7). This isotopic value is less negative than
the anthropogenic source signature (53.2 to 47.5%), but
is indistinguishable from the only quantified natural source
signature (43.0%). Based on known source signatures
and our atmospheric measurements, we predict that the
mean kinetic isotope effect associated with sinks must be
small (24%). We further estimate that a total phaseout of
anthropogenic sources would likely change the
isotopic composition of atmospheric CH3Br by 24%,
and that this change would be difficult to detect with
current measurement techniques. IsoPrime 稳定同位素质谱仪