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| Titel |
Hydrogeochemsitry of montane springs and their influence on streams in the Cairngorm mountains, Scotland |
| VerfasserIn |
C. Soulsby, R. Malcolm, R. Helliwell, R. C. Ferrier |
| 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 ; 3, no. 3 ; Nr. 3, no. 3, S.409-419 |
| Datensatznummer |
250001091
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| Publikation (Nr.) |
 copernicus.org/hess-3-409-1999.pdf |
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| Zusammenfassung |
| Springs are important groundwater discharge points on the high altitude
(>800m) plateaux of the Cairngorm mountains, Scotland and form important
wetland habitats within what is often a dry, sub-arctic landscape. The
hydrogeochemistry of a typical spring in the Allt a'Mharcaidh catchment was
examined between 1995-98 in order to characterise its chemical composition,
identify the dominant controls on its chemical evolution and estimate
groundwater residence time using 18O isotopes. Spring water, sustained by
groundwater flow in shallow drift deposits and fractured bedrock, was moderately
acidic (mean pH 5.89), with a very low alkalinity (mean 18 μeq l-1)
and the ionic
composition was dominated by sea-salts derived from atmospheric sources.
Geochemical modelling using NETPATH, predicted that the dissolution of
plagioclase mainly controls the release of Si, non-marine Na, Ca, K and Al into
spring water. Hydrological conditions influenced seasonal variations in spring
chemistry, with snowmelt associated with more rapid groundwater flows and lower
weathering rates than summer discharges. Downstream of the spring, the chemistry
of surface water was fundamentally different as a result of drainage from larger
catchment areas, with increased soil and drift cover, and higher evaporation
rates. Thus, the hydrogeochemical influence of springs on surface waters appears
to be localized. Mean δ18O values in spring water were lower and more
damped than those in precipitation. Nevertheless, a sinusoidal seasonal pattern
was observed and used to estimate mean residence times of groundwater of around
2 years. Thus, in the high altitude plateau of the Cairngorms, shallow, coarse
drift deposits from significant aquifers. At lower altitudes, deeper drift
deposits, combined with larger catchment areas, increase mean groundwater
residence times to >5 years. At high altitudes, the shallow, permeable nature of
the drifts dictates that groundwater is vulnerable to impacts of environmental
changes that could be usefully monitored at spring sites. |
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