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Investigations of freezing and cold storage for the analysis of peatland dissolved organic carbon (DOC) and absorbance properties

Peacock, Mike; Freeman, Chris; Gauci, Vincent; Lebron, Inma and Evans, Chris D. (2015). Investigations of freezing and cold storage for the analysis of peatland dissolved organic carbon (DOC) and absorbance properties. Environmental Science: Processes & Impacts, 17(7) pp. 1290–1301.

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Although measured rates of biological degradation of DOC are typically low under dark conditions, it is assumed that water samples must be analysed soon after collection to provide an accurate measure of DOC concentration and UV-visible absorbance. To examine the impact of storage on DOC quality and quantity, we took water samples from an ombrotrophic peatland, and stored them in the dark at 4°C for 138 – 1082 days. A median of 29% of DOC was lost during storage, but losses of absorbance at 254 nm were less. DOC loss followed a first-order exponential decay function, and was dependent on storage time. DOC half-life was calculated as 1253 days. Specific absorbance at 254 nm suggested that samples containing more aromatic DOC were more resistant to degradation, although time functioned as the primary control. Samples from two fens showed that loss of absorbance was greater at 25 400 nm rather than 254 nm, after 192 days storage, suggesting that non-aromatic DOC is preferentially degraded. These results suggest that samples can be stored for several months before losses of DOC become detectable, and that it is possible to back-calculate initial DOC concentrations in long-term stored samples based on known decay rates. Freeze/thaw experiments using samples from a range of peatlands suggested that DOC concentration was mostly unaffected by the process, but DOC increased 37% in one sample. Freezing had unpredictable and sometimes strong effects on absorbance, SUVA and E ratios, therefore freezing is not recommended as a method of preservation for these analyses.

Item Type: Journal Item
Copyright Holders: 2015 The Authors
ISSN: 2050-7895
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Research Group: OpenSpace Research Centre (OSRC)
International Development & Inclusive Innovation
Item ID: 43282
Depositing User: Michael Peacock
Date Deposited: 01 Jun 2015 10:40
Last Modified: 22 Mar 2020 15:49
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