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Seasonal photoreactivity of dissolved organic matter from lakes with contrasting humic content

Författare:
  • M Lindell
  • Wilhelm Granéli
  • S Bertilsson
Publiceringsår: 2000
Språk: Engelska
Sidor: 875-885
Publikation/Tidskrift/Serie: Canadian Journal of Fisheries and Aquatic Sciences
Volym: 57
Nummer: 5
Dokumenttyp: Artikel i tidskrift
Förlag: National Research Council Canada

Abstract english

We studied seasonal variability in photodegradation of dissolved organic carbon (DOC) resulting from artificial ultraviolet-A (UV-A) and UV-B irradiation. Water samples were taken approximately monthly from the surface layers of two oligotrophic lakes with contrasting humic content, situated in southern Sweden. Lake water was filter-sterilized (0.2 μm) and exposed to artificial UV radiation in quartz tubes. Potential DOC photodegradation, measured as a photoproduction of dissolved inorganic carbon (DIC) and oxalic, malonic, formic, and acetic acid in irradiated samples, was observed throughout the sampling period. In addition, exposure to UV radiation resulted in a decrease in DOC, absorbance, and humic substance fluorescence. The photoproduction of DIC and the low molecular weight (LMW) organic acids varied seasonally, being generally higher in winter and spring (December-May), while DOC appeared to become less photoreactive after the extensive exposure to solar radiation during summer. Production rates of both DIC and LMW organic acids were approximately eight times higher in the humic lake despite that the DOC concentration was only two times higher than in the clearwater lake. This is most probably due to the high input of allochthonous DOC and the resulting higher absorbance to DOC ratio in the humic system. Furthermore, the longer hydraulic residence time in the clearwater system could have resulted in an accumulation of residual DOC, recalcitrant to further photodegradation.

Keywords

  • Ecology

Other

Published
  • ISSN: 1205-7533
Wilhelm Granéli
E-post: wilhelm [dot] graneli [at] biol [dot] lu [dot] se

Professor emeritus

Akvatisk ekologi

+46 70 279 82 34

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Akvatisk ekologi