Monitoring dissolved organic carbon in Swedish forest streams after wildfire

University essay from SLU/Dept. of Aquatic Sciences and Assessment

Abstract: In situ water quality monitoring devices (sondes) allow monitoring of dissolved organic matter (DOC) continuously at a high resolution via measurements of fluorescent dissolved organic matter (fDOM). Two sondes were used to test the hypothesis that DOC in local streams would decrease in concentration immediately after forest fire. It was expected that the sondes' measurements would be influenced by turbidity and require post hoc correction. A simple model to predict DOC from fDOM was designed and suggested that DOC inputs were reduced after the fire, but flushing of terrestrial carbon brought values back to normal in following spring. Analysis of fluorescence and absorbance suggested a change in the quality as well as quantity of carbon inputs. Sonde measurements were found to be severely affected by high turbidity events, and varied depending on the stream, but we could partially compensate for this with corrections based on laboratory analysis of samples taken from monitored streams. Future monitoring that relies on fDOM data should be supported by a sampling program to capture natural variation of DOC and turbidity in the monitored stream.

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