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| Titel |
A process-based 222radon flux map for Europe and its comparison to long-term observations |
| VerfasserIn |
U. Karstens, C. Schwingshackl, D. Schmithüsen, I. Levin |
| 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. 22 ; Nr. 15, no. 22 (2015-11-19), S.12845-12865 |
| Datensatznummer |
250120171
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| Publikation (Nr.) |
 copernicus.org/acp-15-12845-2015.pdf |
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| Zusammenfassung |
| Detailed 222radon (222Rn) flux maps are an essential pre-requisite
for the use of radon in atmospheric transport studies. Here we present a
high-resolution 222Rn flux map for Europe, based on a parameterization
of 222Rn production and transport in the soil. The 222Rn
exhalation rate is parameterized based on soil properties, uranium content,
and modelled soil moisture from two different land-surface reanalysis data
sets. Spatial variations in exhalation rates are primarily determined by the
uranium content of the soil, but also influenced by soil texture and local
water-table depth. Temporal variations are related to soil moisture
variations as the molecular diffusion in the unsaturated soil zone depends
on available air-filled pore space. The implemented diffusion
parameterization was tested against campaign-based 222Rn soil profile
measurements. Monthly 222Rn exhalation rates from European soils were
calculated with a nominal spatial resolution of 0.083° × 0.083° and compared to long-term direct measurements of 222Rn
exhalation rates in different areas of Europe. The two realizations of the
222Rn flux map, based on the different soil moisture data sets, both
realistically reproduce the observed seasonality in the fluxes but yield
considerable differences for absolute flux values. The mean 222Rn flux
from soils in Europe is estimated to be 10 mBq m−2 s−1 (ERA-Interim/Land soil moisture) or 15 mBq m−2 s−1 (GLDAS (Global Land Data Assimilation System) Noah soil moisture) for
the period 2006–2010. The corresponding seasonal variations with low fluxes
in winter and high fluxes in summer range in the two realizations from ca. 7 to ca. 14 mBq m−2 s−1
and from ca. 11 to ca. 20 mBq m−2 s−1, respectively. These
systematic differences highlight the importance of realistic soil moisture
data for a reliable estimation of 222Rn exhalation rates. Comparison
with observations suggests that the flux estimates based on the GLDAS Noah
soil moisture model on average better represent observed fluxes. |
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