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| Titel |
Characterisation of Dissolved Organic Carbon by Thermal Desorption - Proton Transfer Reaction - Mass Spectrometry |
| VerfasserIn |
Dušan Materić, Mike Peacock, Matthew Kent, Sarah Cook, Vincent Gauci, Thomas Röckmann, Rupert Holzinger |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141606
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| Publikation (Nr.) |
 EGU/EGU2017-5136.pdf |
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| Zusammenfassung |
| Dissolved organic carbon (DOC) is an integral component of the global carbon cycle. DOC
represents an important terrestrial carbon loss as it is broken down both biologically and
photochemically, resulting in the release of carbon dioxide (CO2) to the atmosphere. The
magnitude of this carbon loss can be affected by land management (e.g. drainage).
Furthermore, DOC affects autotrophic and heterotrophic processes in aquatic ecosystems,
and, when chlorinated during water treatment, can lead to the release of harmful
trihalomethanes. Numerous methods have been used to characterise DOC. The most
accessible of these use absorbance and fluorescence properties to make inferences about
chemical composition, whilst high-performance size exclusion chromatography can be used
to determine apparent molecular weight. XAD fractionation has been extensively used to
separate out hydrophilic and hydrophobic components. Thermochemolysis or pyrolysis Gas
Chromatography – Mass Spectrometry (GC-MS) give information on molecular properties
of DOC, and 13C NMR spectroscopy can provide an insight into the degree of
aromaticity.
Proton Transfer Reaction – Mass Spectrometry (PTR-MS) is a sensitive, soft ionisation
method suitable for qualitative and quantitative analysis of volatile and semi-volatile organic
vapours. So far, PTR-MS has been used in various environmental applications such as
real-time monitoring of volatile organic compounds (VOCs) emitted from natural and
anthropogenic sources, chemical composition measurements of aerosols etc. However, as the
method is not compatible with water, it has not been used for analysis of organic traces
present in natural water samples.
The aim of this work was to develop a method based on thermal desorption
PTR-MS to analyse water samples in order to characterise chemical composition of
dissolved organic carbon. We developed a clean low-pressure evaporation/sublimation
system to remove water from samples and thermal desorption system to introduce the
samples to the PTR-MS. With thermal desorption lasting just 5 min (at 200˚ C) we
successfully detected more than 200 organic ions in the water samples yielding
up to 800 ng/mL in total (which corresponds to 1.5% of total DOC present in the
sample). Samples were from tropical peatlands in Borneo and Malaysia. Principle
component analysis showed a clear separation of the samples when comparing intact and
degraded peat swamp forest, and between an oil palm plantation and natural forest.
This suggests that the degradation and conversion of tropical peatlands result in
distinct changes to DOC composition, with possible implications for associated CO2
emissions.
As the method is sensitive and reproducible it has wide potential application in the
characterisation of water and of soils. It could provide important information on how land
management, microbial activity, vegetation and water treatment control the chemical
composition of DOC. |
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