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

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 sout...

Full description

Saved in:
Bibliographic Details
Published in:Canadian journal of fisheries and aquatic sciences 2000-05, Vol.57 (5), p.875-885
Main Authors: Lindell, Måns J, Granéli, H Wilhelm, Bertilsson, Stefan
Format: Article
Language:English
Subjects:
Aquaculture
Biologi
Biological Sciences
Carbon
Dissolved organic carbon
Dissolved organic matter
Ecology
Ecosystems
Ekologi
Irradiation
Lakes
Marine ecosystems
NATURAL SCIENCES
NATURVETENSKAP
Oligotrophic lakes
Oxidation
Photochemistry
Photodegradation
Radiation
Seasonal variations
Seasons
Ultraviolet radiation
Water analysis
Water sampling
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary: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.
ISSN:0706-652X
1205-7533
1205-7533
DOI:10.1139/f00-016