Centennial-scale age offsets of plant wax n-alkanes in Adirondack lake sediments

DO RADIOCARBON AGES OF PLANT WAX BIOMARKERS AGREE WITH 14C-TOC/OSL-BASED AGE MODELS IN AN ARID HIGH-ALTITUDE LAKE SYSTEM?

“…Overall, the mean residence times of n-alkanes, i.e., the offsets of 1000-1900 years between the TOC/OSL-age model and the ages of n-alkanes, are larger than in most previous studies from lacustrine systems (Uchikawa et al 2008;Douglas et al 2014Douglas et al , 2018Gierga et al 2016;Yamamoto et al 2020;Freimuth et al 2021). On the other hand, they are in range of average ages as determined in soils from the Karakul catchment.…”

“…The mean residence times of soil organic matter is believed to be relatively short, i.e., a few decades (Kögel-Knabner and Amelung 2014; Feng et al 2016). However, a number of studies identified a significantly older carbon pool, i.e., several hundreds to a few thousands of years old, which may consist of more recalcitrant or physically stabilized compounds (Schöning and Kögel-Knabner 2006;Smittenberg et al 2006;Trumbore 2009;Douglas et al 2014Douglas et al , 2018Van der Voort et al 2017).…”

“…Lacustrine systems (Uchikawa et al 2008;Douglas et al 2014;Gierga et al 2016;Douglas et al 2018;Aichner et al 2018;Yamamoto et al 2020;Freimuth et al 2021) have been comparably less studied. Also here, ages of plant waxes from catchment soils range from several hundreds to thousands of years at both temperate and warm/humid study sites.…”

Precipitation and Lake Water Evaporation Recorded by Terrestrial and Aquatic n‐Alkane δ2H Isotopes in Lake Khar Nuur, Mongolia

“…Those possibly relocated n ‐alkanes further might question if δ 2 H C31 of the surface sediment samples in Lake Khar Nuur represent a contemporary signal that become deposited shortly after the n ‐alkane formation in the catchment or if those n‐ alkanes are pre‐aged due to residence times in the catchment soils and/or transfer times through the catchment. Such a pre‐aging of terrestrial biomarkers has been previously reported from different lakes around the world, and time lags can be in the order of hundreds to thousands years, and often strongly increase with increased anthropogenic activity in the lake catchment (Douglas et al., 2018; Freimuth et al., 2021; Gierga et al., 2016). In this context, compound‐specific radiocarbon dating provide the opportunity to directly date single terrestrial n ‐alkanes.…”

“…Moreover, the terrestrial n-alkanes might have time lags between their timing of formation and their deposition within the lake because of certain residence times in and transfer times through the catchment. Those transfer times can be in the order of hundreds to thousands of years and have been reported from different lacustrine systems (Aichner et al, 2021;Douglas et al, 2018;Freimuth et al, 2021;Gierga et al, 2016). However, it has been suggested to especially investigate lakes with small hydrological catchments to reduce potential time lags of terrestrial n-alkanes (Bliedtner et al, 2020;Gierga et al, 2016).…”