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| Titel |
Seasonal changes in photochemical properties of dissolved organic matter in small boreal streams |
| VerfasserIn |
P. Porcal, P. J. Dillon, L. A. Molot |
| 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. 8 ; Nr. 10, no. 8 (2013-08-16), S.5533-5543 |
| Datensatznummer |
250085301
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| Publikation (Nr.) |
 copernicus.org/bg-10-5533-2013.pdf |
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| Zusammenfassung |
| The fate of dissolved organic matter (DOM) in lakes and streams is
significantly affected by photochemical transformation of DOM. A series of
laboratory photochemical experiments was conducted to describe seasonal
changes in photochemical properties of DOM. The stream samples used in this
study originated from three different catchments in the southernmost part of
the Boreal ecozone near Dorset, Ontario, Canada. A first-order kinetics
equation was used to model photochemical degradation of DOM and the kinetic
rate constant, K, was used as an indicator of photochemical properties of
DOM. Kinetic rate constants from all three catchments showed a sinusoidal
pattern during the hydrological year. K increased steadily during autumn
and winter and decreased during spring and summer with a more than 3-fold
range in each stream. The highest values were observed during spring melt
events when DOM was flushed from terrestrial sources by high flows. The
minimum rate constants were found in summer when discharge was lowest. K
was strongly correlated with pH and iron. DOM molecular weight and specific
absorbance at 254 nm also exhibited annual cycles corresponding to the
seasonal cycles of terrestrial organic matter, but the relationships between
these properties and K differed between seasons and may have been affected
by previous exposure to solar radiation during transit from the catchment. |
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