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| Titel |
Increasing iron concentrations in surface waters – a factor behind brownification? |
| VerfasserIn |
E. S. Kritzberg, S. M. Ekström |
| 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 ; 9, no. 4 ; Nr. 9, no. 4 (2012-04-20), S.1465-1478 |
| Datensatznummer |
250006954
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| Publikation (Nr.) |
 copernicus.org/bg-9-1465-2012.pdf |
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| Zusammenfassung |
| Browning of inland waters has been noted over large parts of the Northern
hemisphere and is a phenomenon with both ecological and societal
consequences. The increase in water color is generally ascribed to
increasing concentrations of dissolved organic matter of terrestrial origin.
However, oftentimes the increase in water color is larger than that of
organic matter, implying that changes in the concentration of organic matter
alone cannot explain the enhanced water color. Water color is known to be
affected also by the quality of organic matter and the prevalence of iron.
Here we investigated trends in water color, organic matter and iron between
1972 and 2010 in 30 rivers draining into the Swedish coast (data from the
national Swedish monitoring program), and performed a laboratory iron
addition experiment to natural waters, to evaluate the role of iron and
organic matter in determining water color. By comparing the effect of iron
additions on water color in the experiment, to variation in water color and
iron concentration in the monitoring data, we show that iron can explain a
significant share of the variation in water color (on average 25 %),
especially in the rivers in the north of Sweden (up to 74 %).
Furthermore, positive trends for iron are seen in 27 of 30 rivers (21–468 %) and the increase in iron is larger than that of organic matter,
indicating that iron and organic matter concentrations are controlled by
similar but not identical processes. We speculate that increasing iron
concentrations can be caused by changes in redox conditions, that mean that
more anoxic water with high concentrations of soluble FeII are feeding into
the surface waters. More studies are needed about why iron is increasing so
strongly, since both causes and consequences are partly different from those
of increasing organic matter content. |
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