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

Lindell, M; Granéli, Wilhelm LU and Bertilsson, S (2000) In Canadian Journal of Fisheries and Aquatic Sciences 57(5). p.875-885
Abstract
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... (More)
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. (Less)
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published
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in
Canadian Journal of Fisheries and Aquatic Sciences
volume
57
issue
5
pages
875 - 885
publisher
National Research Council Canada
external identifiers
  • scopus:0033927523
ISSN
1205-7533
language
English
LU publication?
yes
id
43df004e-70ce-4045-ab66-ea570b6e8eaa (old id 149783)
alternative location
http://rpas.web-p.cisti.nrc.ca/RPAS/RPViewDoc?_handler_=HandleInitialGet&journal=cjfas&volume=57&calyLang=eng&articleFile=f00-016.pdf
date added to LUP
2007-06-28 14:24:23
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2017-10-01 03:42:19
@article{43df004e-70ce-4045-ab66-ea570b6e8eaa,
  abstract     = {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.},
  author       = {Lindell, M and Granéli, Wilhelm and Bertilsson, S},
  issn         = {1205-7533},
  language     = {eng},
  number       = {5},
  pages        = {875--885},
  publisher    = {National Research Council Canada},
  series       = {Canadian Journal of Fisheries and Aquatic Sciences},
  title        = {Seasonal photoreactivity of dissolved organic matter from lakes with contrasting humic content},
  volume       = {57},
  year         = {2000},
}