Effects of handling, storage, and chemical treatments on δ¹³C values of terrestrial fossil organic matter

Abstract

With the need to interpret small isotopic variations, δ13C analyses of sedimentary organic matter are more and more widespread in the field of (paleo)climatology. Recent developments require an evaluation of the reliability and reproducibility of the whole data acquisition chain. Literature abounds in protocols for sediment pretreatment prior to physical measurements. These procedures differ at every step: from sampling, handling, and storage conditions to leaching procedure, without cross evaluation. In this study, we focus on two sediment samples: a modern temperate soil and a 70 ka typical loess. We review different protocols that characterize each step of the sediment pretreatment. Handling and storage conditions are tested, e.g., finger skin contact, mild‐ to high‐temperature oven‐dry, and freeze‐drying. Likewise, different decarbonation protocols are compared: wet decarbonation under cold 0.6 N HCl, 2 N HCl and boiling 1 N HCl, and acid fuming with 36% HCl. This study identifies up to 1.5‰ isotopic shifts linked to experimental bias. This large bias might be at the origin of erroneous paleoclimatic interpretation. On the basis of these results, we propose specific treatments adapted to the sample type.

Geomorphic response and 14C chronology of base-level changes induced by Late Quaternary Caspian Sea mobility (middle Kura Valley, Azerbaijan)

“…Sediments were then sieved using meshes smaller than 250 μm to remove possible roots. The fine fraction was decarbonated with 0.6 N HCl (Gauthier and Hatté, 2008), rinsed, dried at 50°C, and homogenized. The samples were then combusted at 900°C in an evacuated quartz tube with copper oxide and silver foil.…”

Excursions to C<sub>4</sub> vegetation recorded in the Upper Pleistocene loess of Surduk (Northern Serbia): an organic isotope geochemistry study

“…The sediment samples were dried at low temperature as soon as possible to ensure safe storage, as recommended by Gauthier and Hatté (2008). After being sieved at 250 µm to remove stones and being homogenized, the sediment then underwent a soft leaching process to remove carbonate using pre-combusted glass beakers, HCl 0.6 N at room temperature, ultra-pure water and drying at 50 • C. The samples were then crushed in a pre-combusted glass mortar for homogenization prior to carbon content and δ 13 C analysis.…”

Climate reconstruction from pollen and δ<sup>13</sup>C records using inverse vegetation modeling – Implication for past and future climates

“…This induces that an upstream error that can derived from an unadequate handling of one or both records would be perpetuated through the inverse modeling procedure. As an example, unadequate procedure prior geochemical measurements (Gauthier and Hatté, 2008) or the presence of absence of a single pollen grain of a single taxon in the pollen counts can cause a change in the biome that is identified by the biomisation technique. Improvements for future studies would be to use the abundance of plant functional types identified in the pollen spectra (PFT-scores) instead of biomes (Davis et al, 2003).…”