Stable hydrogen isotope ratios of lignin methoxyl groups as a paleoclimate proxy and constraint of the geographical origin of wood

Abstract

Summary• Stable isotope ratios of organic compounds are valuable tools for determining the geographical origin, identity, authenticity or history of samples from a vast range of sources such as sediments, plants and animals, including humans.• Hydrogen isotope ratios ( δ 2 H values) of methoxyl groups in lignin from wood of trees grown in different geographical areas were measured using compound-specific pyrolysis isotope ratio mass spectrometry analysis.• Lignin methoxyl groups were depleted in 2 H relative to both meteoric water and whole wood. A high correlation ( r 2 = 0.91) was observed between the δ 2 H values of the methoxyl groups and meteoric water, with a relatively uniform fractionation of -216 ± 19‰ recorded with respect to meteoric water over a range of δ 2 H values from -110 in northern Norway to + 20‰ in Yemen. Thus, woods from northern latitudes can be clearly distinguished from those from tropical regions. By contrast, the δ 2 H values of bulk wood were only relatively poorly correlated ( r 2 = 0.47) with those of meteoric water.• Measurement of the δ 2 H values of lignin methoxyl groups is potentially a powerful tool that could be of use not only in the constraint of the geographical origin of lignified material but also in paleoclimate, food authenticity and forensic investigations.

A mathematical analysis of the divergence problem in dendroclimatology

“…Finally, a promising new method is the use of δ 2 H isotope ratios in wood (Keppler et al 2007). These isotope ratios can be calibrated to the temperature of rain water and can at the same time be precisely dated by the tree rings.…”

Water drives the deuterium content of the methane emitted from plants

“…Recent studies have demonstrated the tight correlation between the dD of methoxyl groups and dD in the precipitation in the area where the plants grew (the latter was not directly measured, but calculated using the Online Isotope Precipitation Calculator, (OIPC) (Keppler et al, 2007;Keppler and Hamilton, 2008). This offers the potential to use the isotope signature of methoxyl groups as a paleoclimate proxy (Keppler et al, 2007).…”

“…This offers the potential to use the isotope signature of methoxyl groups as a paleoclimate proxy (Keppler et al, 2007). Methoxyl groups, especially from lignin, are considered to be stable with no exchange of hydrogen with water (Keppler et al, 2007).…”

Methoxyl groups of plant pectin as a precursor of atmospheric methane: evidence from deuterium labelling studies

“…Methoxyl content was determined by measuring the release of methyl iodide (CH 3 I) using the Zeisel technique as described by Keppler et al (2007). Incorporation of the deuterium label of the ester group in pectin and modified PGAs was also determined using CH 3 I.…”

“…Stable isotope analysis is a powerful tool that we recently employed to demonstrate that plant pectin and lignin methoxyl groups have unique carbon isotope signatures (Keppler et al, 2004), and also to establish the relationship between hydrogen isotopes of wood lignin methoxyl groups and meteoric water (Keppler et al, 2007). In this investigation we again employ this technique, together with pectin and polygalacturonic acid (PGA) (Fig.…”