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| Titel |
Increasing concentrations of dichloromethane, CH2Cl2, inferred from CARIBIC air samples collected 1998–2012 |
| VerfasserIn |
E. C. Leedham Elvidge, D. E. Oram, J. C. Laube, A. K. Baker, S. A. Montzka, S. Humphrey, D. A. O'Sullivan, C. A. M. Brenninkmeijer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 4 ; Nr. 15, no. 4 (2015-02-24), S.1939-1958 |
| Datensatznummer |
250119452
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| Publikation (Nr.) |
 copernicus.org/acp-15-1939-2015.pdf |
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| Zusammenfassung |
| Atmospheric concentrations of dichloromethane, CH2Cl2, a regulated
toxic air pollutant and minor contributor to stratospheric ozone depletion,
were reported to have peaked around 1990 and to be declining in the early
part of the 21st century. Recent observations suggest this trend has
reversed and that CH2Cl2 is once again increasing in the atmosphere.
Despite the importance of ongoing monitoring and reporting of atmospheric
CH2Cl2, no time series has been discussed in detail since 2006.
The CARIBIC project (Civil Aircraft for the Regular Investigation of the
atmosphere Based on an Instrument Container) has analysed the halocarbon
content of whole-air samples collected at altitudes of between
~ 10–12 km via a custom-built container installed on
commercial passenger aircraft since 1998, providing a long-term record of
CH2Cl2 observations. In this paper we present this unique
CH2Cl2 time series, discussing key flight routes which have been
used at various times over the past 15 years. Between 1998 and 2012
increases were seen in all northern hemispheric regions and at different
altitudes, ranging from ~ 7–10 ppt in background air to
~ 13–15 ppt in regions with stronger emissions (equating to a
38–69% increase). Of particular interest is the rising importance of
India as a source of atmospheric CH2Cl2: based on CARIBIC data we
provide regional emission estimates for the Indian subcontinent and show
that regional emissions have increased from 3–14 Gg yr−1 (1998–2000) to
16–25 Gg yr−1 (2008). Potential causes of the increasing atmospheric
burden of CH2Cl2 are discussed. One possible source is the
increased use of CH2Cl2 as a feedstock for the production of
HFC-32, a chemical used predominantly as a replacement for ozone-depleting
substances in a variety of applications including air conditioners and
refrigeration. |
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