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| Titel |
Long-term and seasonal variations in CO2: linkages to catchment alkalinity generation |
| VerfasserIn |
S. A. Norton, B. J. Cosby, I. J. Fernandez, J. S. Kahl, M. Robbins Church |
| 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 ; 5, no. 1 ; Nr. 5, no. 1, S.83-91 |
| Datensatznummer |
250002257
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| Publikation (Nr.) |
 copernicus.org/hess-5-83-2001.pdf |
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| Zusammenfassung |
| As atmospheric emissions of S have declined
in the Northern Hemisphere, there has been an expectation of increased pH and
alkalinity in streams believed to have been acidified by excess S and N. Many
streams and lakes have not recovered. Evidence from East Bear Brook in Maine,
USA and modelling with the groundwater acid-base model MAGIC (Cosby et al. 1985a,b)
indicate that seasonal and yearly variations in soil PCO2 are
adequate to enhance or even reverse acid-base (alkalinity) changes anticipated
from modest decreases of SO4 in surface waters. Alkalinity is
generated in the soil by exchange of H+ from dissociation of H2CO3,
which in turn is derived from the dissolving of soil CO2. The
variation in soil PCO2 produces an alkalinity variation of up to
15 meq L-1 in stream water. Detecting and relating increases in
alkalinity to decreases in stream SO4 are significantly more
difficult in the short term because of this effect. For example, modelled
alkalinity recovery at Bear Brook due to a decline of 20 meq SO4 L-1
in soil solution is compensated by a decline from 0.4 to 0.2% for soil air PCO2.
This compensation ability decays over time as base saturation declines.
Variable PCO2 has less effect in more acidic soils. Short-term
decreases of PCO2 below the long-term average value produce
short-term decreases in alkalinity, whereas short-term increases in PCO2
produce short-term alkalization. Trend analysis for detecting recovery of
streams and lakes from acidification after reduced atmospheric emissions will
require a longer monitoring period for statistical significance than previously
appreciated.
Keywords: CO2 , alkalinity, acidification,
recovery, soils, climate change |
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