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| Titel |
Long-term patterns in dissolved organic carbon, major elements and trace metals in boreal headwater catchments: trends, mechanisms and heterogeneity |
| VerfasserIn |
S. K. Oni, M. N. Futter, K. Bishop, S. J. Köhler, M. Ottosson-Löfvenius, H. Laudon |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 4 ; Nr. 10, no. 4 (2013-04-08), S.2315-2330 |
| Datensatznummer |
250018186
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| Publikation (Nr.) |
 copernicus.org/bg-10-2315-2013.pdf |
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| Zusammenfassung |
| The boreal landscape is a complex, spatio-temporally varying mosaic of
forest and mire landscape elements that control surface water hydrology and
chemistry. Here, we assess long-term water quality time series from three
nested headwater streams draining upland forest (C2), peat/mire (C4) and
mixed (C7) (forest and mire) catchments. Acid deposition in this region is
low and is further declining. Temporal trends in weather and runoff
(1981–2008), dissolved organic carbon concentration [DOC] (1993–2010) and
other water quality parameters (1987–2011) were assessed. There was no
significant annual trend in precipitation or runoff. However, runoff
increased in March and declined in May. This suggested an earlier snowmelt
regime in recent years. Significant monotonic increasing trends in air
temperature and length of growing season suggested a decrease in snowfall
and less spring runoff. Stream [DOC] was positively correlated with some
trace metals (copper, iron and zinc) and negatively with several other
chemical parameters (e.g. sulfate, conductivity, calcium). Both sulfate and
conductivity showed declining trends, while a significant increase was
observed in pH during winter and spring. Calcium and magnesium showed
monotonic decreasing trends. The declining trajectories of stream base
cation and sulfate concentrations during other times of the year were not
accompanied by changes in pH and alkalinity. These results indicate subtle
effects of recovery from acidification. Water temperature increased
significantly both annually and in most months. A simultaneous monotonic
increase in iron (Fe) and [DOC] in autumn suggests co-transport of Fe-DOC in
the form of organometallic complexes. A monotonic increase in UV absorbance
in most months without co-occurring changes in DOC trend suggests a shift in
DOC quality to a more humic-rich type. The observed increase in soil
solution [DOC] and subtle trends in stream [DOC] suggest that climate rather
than recovery from acidification is the dominant driver of DOC trends in the
Svartberget catchment. |
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