 |
| Titel |
Grass material as process standard for compound-specific radiocarbon analysis |
| VerfasserIn |
Malu Cisneros-Dozal, Xiaomei Xu, Charlotte Bryant, Emma Pearson, Jennifer Dungait |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250102257
|
| Publikation (Nr.) |
 EGU/EGU2015-1566.pdf |
|
|
|
|
|
| Zusammenfassung |
| Compound-specific radiocarbon analysis (CSRA) is a powerful tool to study the carbon cycle
and/or as a dating technique in paleoclimate reconstructions. The radiocarbon value of
individual compounds can provide insight into turnover times, organic matter sources
and in specific cases can be used to establish chronologies when traditional dating
materials (e.g. macrofossils, pollen, charcoal) are not available. The isolation of
compounds (or group of compounds) from parent material (e.g. soil, plant) for
radiocarbon analysis can, however, introduce carbon contamination through chemical
separation steps and preparative capillary gas chromatography (PCGC). In addition, the
compounds of interest are often in low abundance which amplifies the contamination
effect. The extraneous carbon can be of modern 14C age and/or 14C -free and its
amount and 14C value must be determined for a given system/isolation procedure
in order to report accurate 14C values. This can be achieved by using adequate
standard materials but, by contrast with traditional radiocarbon dating, there are
not established reference standards for CSRA work, in part because the type of
standard material depends on the compounds of interest and the isolation procedure.
Here we evaluate the use of n-alkanes extracted from single-year growth grass
as modern process standard material for CSRA using PCGC isolation. The grass
material has a known 14C value of 1.224 ± 0.006 fraction modern (FM) and the
individual n-alkanes are expected to have a similar 14C value. In order to correct for the
addition of extraneous carbon during PCGC isolation of the n-alkanes, we used
commercially available compounds of modern 14C content and 14C -free (adipic
acid, FM= 0.0015 ± 0.0001 and docosane, FM=1.059 ± 0.003) to evaluate our
PCGC procedure. The corrected 14C values of the isolated n-alkanes extracted from
the modern grass are within one sigma of the grass bulk 14C value for n-C29 and
within two sigma for n-C23-C27, C31 and C33. Our results show that single-year
growth grass can be a process standard suitable for quality control of extraction of
n-alkanes (and potentially other compounds) from soil or plant material for CSRA. |
|
|
|
|
|
|