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| Titel |
Future recovery of acidified lakes in southern Norway predicted by the MAGIC model |
| VerfasserIn |
R. F. Wright, B. J. Cosby |
| 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 ; 7, no. 4 ; Nr. 7, no. 4, S.467-483 |
| Datensatznummer |
250004705
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| Publikation (Nr.) |
 copernicus.org/hess-7-467-2003.pdf |
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| Zusammenfassung |
| The acidification model MAGIC was used to predict recovery of small lakes in
southernmost Norway to future reduction of acid deposition. A set of 60 small headwater
lakes was sampled annually from either 1986 (35 lakes) or 1995 (25 lakes). Future acid
deposition was assumed to follow implementation of current agreed legislation, including
the Gothenburg protocol. Three scenarios of future N retention were used. Calibration of
the sites to the observed time trends (1990–1999) as well as to one point in time
considerably increased the robustness of the predictions. The modelled decline in
SO4* concentrations in the lakes over the period 1986–2001 matched
the observed decline closely. This strongly suggests that soil processes such as
SO4 adsorption/desorption and S reduction/oxidation do not delay the response
of runoff by more than a few years. The slope of time trends in ANC over the period of
observations was less steep than that observed, perhaps because the entire soil column
does not interact actively with the soilwater that emerges as runoff. The lakes showed
widely differing time trends in NO3 concentrations over the period 1986–2000.
The observed trends were not simulated by any of the three N scenarios. A model based on
the C/N ratio in soil was insufficient to account for N retention and leaching at these
sites. The large differences in modelled NO3, however, produced only minor
differences in ANC between the three scenarios. In the year 2050, the difference was
only about 5 μeq l-1. Future climate change entailing warming and increased precipitation
could also increase NO3 loss to surface waters. SO4*
concentrations in the lakes were predicted to decrease in parallel with the future
decreases in S deposition. Fully 80% of the expected decline to year 2025, however, had
already occurred by the year 2000. Similarly, ANC concentrations were predicted to
increase in the future, but again about 67% of the expected change has already occurred
over the past 20 years. The recovery of ANC was predicted to be incomplete. Even after
the CLE scenario (for future acid deposition) is implemented, the chemical conditions
in about one-third of the lakes were predicted to be insufficient to support trout
populations in the future. Thus, additional measures will be required if these lakes
are to be restored.
Keywords: acid deposition, lakes, model, Norway, recovery |
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