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| Titel |
Hydrological characterisation of stalagmite dripwaters at Grotte de Villars, Dordogne, by the analysis of inorganic species and luminescent organic matter |
| VerfasserIn |
A. Baker, D. Genty, I. J. Fairchild |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 4, no. 3 ; Nr. 4, no. 3, S.439-449 |
| Datensatznummer |
250001751
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| Publikation (Nr.) |
 copernicus.org/hess-4-439-2000.pdf |
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| Zusammenfassung |
Five stalagmite drip-waters in the Grotte de Villars, Dordogne, have
been monitored
from early 1997 to early 1998, for variations in discharge, major inorganic
species and dissolved luminescent organic matter. When compared to surface
precipitation, each drip-water has a subtly different response, both in terms of
discharge variability and lag time between surface precipitation and drip rate
response. Calculated water excess is shown to be important in determining
drip-water discharge; during periods of soil moisture deficit, drip-waters
either show no response to surface precipitation, or in the case of one sample
station, respond only to high intensity and/or high quantity precipitation
events.
All drip-waters have
a large storage component to their flow. Four sample stations have a similar
hydrochemical and luminescence response, although the precise timing and
magnitude of the responses may vary between drip sources that are <5 m apart.
Drip-water luminescence intensity increases in winter and spring, and increases
in discharge lag by 2 – 3 months, suggesting that the water in the rising limb
and peak of the winter discharge comes from the stored groundwater component
rather than a soil source. Drip-water strontium anti-correlates with
luminescence and exhibits a strong (±100%) seasonal variation, with
high-strontium waters derived from stored groundwater and is inferred to
originate in localised Sr-rich primary components in the limestone.
Drip-water
conductivity reflects Ca-HCO3 variations and falls during late summer to autumn,
which is inferred to result from increased calcite precipitation above the cave
with enhanced degassing related to progressive drying of the aquifer. Drip-water
magnesium (following removal of the marine aerosol component) is just above
detection limits and does not show strong seasonal variations. Variations in
solution Pco2 occur, with a particularly strong increase in early 1997. The
various chemical trends are observed at a number of different sites despite a
pronounced variation between them in terms of total Ca-HCO3 mineralisation and
Pco2.
One sampling station of the five investigated had a different response to surface
precipitation; drip
discharge was more variable, with evidence of non-linear responses, and
luminescence intensity exhibited a dilution response to drip rate. For this
site, flow switching occurred at times of high rainfall, with a rapid discharge
response less than 24 hours after rainfall.
Luminescence
intensity, inorganic chemistry, and discharge characteristics at the site are
compared with results published from other cave systems; significant inter-site
variability depends on the geology, depth of sample sites and extent of
karstification. This suggests that the interpretation of stalagmite
luminescence, and variations in Sr, Ca and Mg must be considered on a site by
site basis.
Keywords: stalagmite; dripwaters; luminescence; discharge; major ion chemistry |
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