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| Titel |
Continuous determination of land-atmosphere Hg0 exchange using a novel Relaxed Eddy Accumulation design |
| VerfasserIn |
Stefan Osterwalder, Johannes Fritsche, Mats B. Nilsson, Christine Alewell, Kevin Bishop |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250105761
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| Publikation (Nr.) |
 EGU/EGU2015-5324.pdf |
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| Zusammenfassung |
| The fate of anthropogenic emissions to the atmosphere is influenced by the exchange of
elemental mercury (Hg0) with the earth surface. However, it remains challenging to quantify
these exchanges which hold the key to a better understanding of mercury cycling at different
scales, from the entire earth to specific environments. To better test hypotheses about
land-atmosphere Hg interactions, we applied dynamic flux chambers (DFCs) for short term
measurements and developed a novel Relaxed Eddy Accumulation (REA) design for
continuous flux monitoring. Accurate determination of Hg0 fluxes has proven difficult due to
the technical challenges presented by the small concentration differences (< 1 ng m-3)
between updrafts and downdrafts. To address this we present a dual-intake, single
analyzer REA system including a calibration module for periodic quality-control
measurements with reference gases. To demonstrate the system performance, we present
results from two contrasting environments: In February 2012 REA monitored a
heterogeneous urban surface in the center of Basel, Switzerland where an average flux
of 14 ng m-2 h-1 was detected with a distinct diurnal pattern. In May 2012, the
REA monitored a boreal mire in northern Sweden with different turbulence regimes
and Hg0 sink/source characteristics. During the snowmelt period in May 2012 the
Hg0 flux averaged at 2 ng m-2 h-1. In order to better quantify inputs and outputs
of Hg from boreal landscapes, we subsequently monitored the land-atmosphere
exchange of Hg0 during a course of a year and compared the fluxes occasionally with
DFC measurements. The amount of Hg0 volatilized from boreal mires was at a
similar level as the annual export of Hg in stream water, identifying the mire as net
source of Hg to neighboring environments. We believe that this dual-inlet, single
detector approach is a significant innovation which can help realize the potential of
REA for continuous, long-term determination of land-atmosphere Hg0 exchange. |
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