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| Titel |
Long-term CH3Br and CH3Cl flux measurements in temperate salt marshes |
| VerfasserIn |
E. Blei, M. R. Heal, K. V. Heal |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 7, no. 11 ; Nr. 7, no. 11 (2010-11-12), S.3657-3668 |
| Datensatznummer |
250005062
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| Publikation (Nr.) |
 copernicus.org/bg-7-3657-2010.pdf |
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| Zusammenfassung |
| Fluxes of CH3Br and CH3Cl and their
relationship with potential drivers such as sunlight,
temperature and soil moisture, were monitored at fortnightly
to monthly intervals for more than two years at two
contrasting temperate salt marsh sites in
Scotland. Manipulation experiments were conducted to further
investigate possible links between drivers and fluxes. Fluxes
followed both seasonal and diurnal trends with highest fluxes
during summer days and lowest (negative) fluxes during winter
nights. Mean
(± 1 sd) annually and diurnally-weighted net emissions
from the two sites were found to be
300 ± 44 ng m−2 h−1 for CH3Br and
662 ± 266 ng m−2 h−1 for
CH3Cl. The fluxes from this work are similar to findings from this and other research groups for salt marshes in cooler, higher latitude climates, but lower than values
from salt marshes in the Mediterranean climate of southern California. Statistical analysis generally did not demonstrate
a strong link between temperature or sunlight levels and
methyl halide fluxes, although it is likely that temperatures
have a weak direct influence on emissions, and both certainly
have indirect influence via the annual and daily cycles of the
vegetation. CH3Cl flux magnitudes from different
measurement locations depended on the plant species enclosed
whereas such dependency was not discernible for CH3Br
fluxes. In 14 out of 18 collars with vegetation CH3Br and
CH3Cl net fluxes were significantly positively correlated. The
CH3Cl/CH3Br net-emission mass ratio was 2.2,
a magnitude lower than mass ratios of global methyl halide
budgets (~22) or emissions from tropical rainforests
(~60). This is likely due to preference for CH3Br
production by the relatively high bromine content in the salt
marsh plant material. Extrapolation based solely on data from this study yields salt
marsh contributions of 0.5–3.2% and 0.05–0.33%, respectively, of currently-estimated
total global production of CH3Br and CH3Cl, but actual global contributions
likely lie between these values and those derived from southern California. |
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