Understanding Dissolved Organic Matter Reactivity and Composition in Lakes and Streams Using Proton-Transfer-Reaction Mass Spectrometry (PTR-MS)

Mike Peacock*, Dušan Materić, Dolly N. Kothawala, Rupert Holzinger, Martyn N. Futter

*Corresponding author for this work

Research output: Contribution to journalLetterAcademicpeer-review

Abstract

Here, we present a novel approach for investigating dissolved organic matter (DOM) composition using thermal desorption proton-transfer-reaction mass spectrometry (PTR-MS), a technique that provides insight into the molecular composition of DOM < m/z 500 (termed "PTR-DOC"). The applicability of PTR-MS for understanding the relationship between DOM composition and reactivity has yet to be explored. We present results from a synoptic sampling campaign of streams and lakes in a Swedish forest catchment where we measured DOM composition using PTR-MS and traditional optical methods and conducted DOM biodegradability assays. PTR-DOC comprised ≤12% of the total DOC pool. We found significant relationships between PTR-DOC and DOM degradability; reduced chemodiversity and low concentrations of PTR-DOC were both associated with the total DOM pool being more susceptible to microbial degradation. Furthermore, molecular differences were apparent among headwater lakes, headwater streams, and lakes further down the catchment. Direct linkages between PTR-DOC and optical methods were observed. Using the quantitative data that PTR-MS generates, it could become possible to identify the fluorescing components of DOM, and the method may be particularly informative in low-DOC waters such as marine environments where PTR-DOC may dominate the total DOM pool.

Original languageEnglish
Pages (from-to)739-744
Number of pages6
JournalEnvironmental Science and Technology Letters
Volume5
Issue number12
DOIs
Publication statusPublished - 11 Dec 2018

Funding

D.M. acknowledges the support of The Netherlands Earth System Science Centre (NESSC) research network. The authors thank Susan Peacock who took part in the sampling campaign. At SLU, the authors thank Stephan Köhler and Claudia Cascone for providing use of the TOC analyzer and assistance with analysis. The authors thank Filip Moldan at the IVL Swedish Environmental Research Institute for logistical support and Daniel Mayor at the UK National Oceanography Centre for the loan of the PreSens system. The authors thank three anonymous reviewers who all provided useful comments and insights that significantly improved the manuscript. Finally, the authors acknowledge Chris Evans of CEH who instigated the sampling program.

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