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| Titel |
Recovery of acidified Finnish lakes: trends, patterns and dependence of catchment characteristics |
| VerfasserIn |
J. Vuorenmaa, M. Forsius |
| 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 ; 12, no. 2 ; Nr. 12, no. 2 (2008-03-05), S.465-478 |
| Datensatznummer |
250010569
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| Publikation (Nr.) |
 copernicus.org/hess-12-465-2008.pdf |
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| Zusammenfassung |
| The regional-scale trends (south, central and north Finland) in key
acidification parameters over the period 1990–2003 were studied in lakes
used for monitoring of acidification (157 lakes), and the catchment
characteristics that best discriminate between lakes showing recovery
(significant increase in alkalinity) and those not showing recovery (no
significant increase) were determined. A significant decline in sulphate
concentrations occurred in 82–98% of the lakes, depending of the region.
Base cation (BC) concentrations decreased for most lakes, but to a lesser
extent than those of SO4. Consequently, a significant increase in Gran
alkalinity occurred in 40–92% of the lakes. The recovery from
acidification has been strongest in lakes in south Finland, where both
levels and decrease of S (and N) deposition have been higher compared to
other regions. A significant increase in pH was detected in about 50% of
the lakes in the south. Here labile aluminium concentrations also decreased
in the most acidic lakes. Recovery has occurred most strongly in lakes which
have SO4 as a dominant acid anion, whereas recovery has been weaker in
acidified humic lakes which have organic anion as a dominant acid anion. The
non-recovering lakes in south Finland have higher proportion of exposed
bedrock in the catchment, and higher TOC and lower BC concentrations. In
central Finland the proportion of peatland and TOC concentrations were
higher and the decrease of BC concentration was steeper in non-recovering
lakes than in recovering lakes. In north Finland, catchment characteristics,
trend slopes and concentrations did not separate the recovering and
non-recovering lakes. The non-recovering lakes were also located in regions
which are acid-sensitive based on bedrock type, soil properties, weathering
rate and runoff. These factors have resulted in lower concentrations and
steeper downward trends for base cations. Climate change may increase the
mineralization of soil organic matter and change the frequency and magnitude of runoff and
organic acid episodes. An increase of these types of confounding effects on pH and alkalinity
recovery may therefore be anticipated in the future. |
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