Total Organic Carbon (TOC) of Lake Water During the Holocene Inferred from Lake Sediments and Near-infrared Spectroscopy (NIRS) in Eight Lakes from Northern Sweden |
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Authors: | Email author" target="_blank">Peter?RosénEmail author |
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Institution: | (1) Climate Impacts Research Centre, SE-981 07 Abisko, Sweden |
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Abstract: | The aim of this study is to infer past changes in total organic carbon (TOC) content of lake water during the Holocene in
eight boreal forest, tree-limit and alpine lakes using a new technique – near-infrared spectroscopy (NIRS). A training set
of 100 lakes from northern Sweden covering a TOC gradient from 0.7 to 14.9 mg l−1 was used to establish a relationship between the NIRS signal from surface sediments (0–1 cm) and the TOC content of the water
mass. The NIRS model for TOC has a root mean squared error (RMSECV) of calibration of 1.6 mg l−1 (11% of the gradient) assessed by internal cross-validation (CV), which yields an R2cv of 0.61. The results show that the most dramatic change among the studied lakes occurs in both tree-line lakes around 1000 yrs
BP when the TOC content decreases from ca. 7 to 3 mg l−1 at the present, which is probably due to a descending tree-limit. The TOC content in the alpine lakes shows a declining trend
throughout most of the Holocene indicating that TOC may be more directly correlated to climate in alpine lakes than forest
lakes. All boreal forest lakes show a declining trend in TOC during the past 3000 yrs with the largest amplitude of change
occurring in the lake with a connected mire. The results indicate that a change to a warmer and more humid climate can increase
the TOC levels in lakes, which in turn may increase the saturation of CO2 in lake waters and the emission of CO2 to the atmosphere. |
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Keywords: | Carbon cycling Climate change CO2 emission Lake sediment Near-infrared spectroscopy Palaeoclimatology |
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