Issue 7, 2015

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

Abstract

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 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.

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

Article information

Article type
Paper
Submitted
19 Marts 2015
Accepted
28 Maijs 2015
First published
29 Maijs 2015
This article is Open Access
Creative Commons BY license

Environ. Sci.: Processes Impacts, 2015,17, 1290-1301

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

M. Peacock, C. Freeman, V. Gauci, I. Lebron and C. D. Evans, Environ. Sci.: Processes Impacts, 2015, 17, 1290 DOI: 10.1039/C5EM00126A

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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