AUTHOR=Shen Zhongwei , Zhang Zhiping , Chen Jie , Chen Lin , Pang Xin , Chen Ruijin , Liu Jianbao , Chen Shengqian 

TITLE=Investigation of Modern n-Alkanes in Daihai Lake Basin, Northern China: Implications for the Interpretation of Paleoclimate Research

JOURNAL=Frontiers in Earth Science

VOLUME=10

YEAR=2022

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.915500

DOI=10.3389/feart.2022.915500

ISSN=2296-6463

ABSTRACT=<p><italic>n</italic>-Alkanes are one of the most used proxies in lake sediments to reconstruct past climate change. However, the distribution and concentration of <italic>n</italic>-alkanes are controlled by multiple factors, and their interpretation across northern China has revealed obvious discrepancies. It is therefore important to investigate the controlling factors of <italic>n</italic>-alkane proxies before using them for paleoclimate reconstruction. In this study, we collected fresh plant leaves, basin surface soils, lake surface sediments, and a short sediment core (DH20B) in the Daihai Lake basin to analyze the paleoclimate implications of <italic>n</italic>-alkanes. Our results show that long-chain (C<sub>27</sub>–C<sub>35</sub>) <italic>n</italic>-alkanes in Daihai Lake are dominated by allochthonous sources. The average chain length of long-chain <italic>n</italic>-alkanes (ACL<sub>27–35</sub>) and total long-chain <italic>n</italic>-alkane concentration (∑alk<sub>long-chain</sub>) of DH20B are significantly correlated with regional summer temperature (<italic>r</italic> = 0.54, <italic>p &lt;</italic> 0.01) and summer precipitation (<italic>r</italic> = 0.41, <italic>p</italic> &lt; 0.05) over the past 60 years. These results indicate that ACL<sub>27–35</sub> and ∑alk<sub>long-chain</sub> from Daihai Lake sediments have the potential to reconstruct past summer temperature and summer precipitation, respectively, because higher summer temperature promotes the synthesis of longer-chain <italic>n</italic>-alkanes to reduce water loss (leading to higher ACL<sub>27–35</sub>) and increased summer precipitation promotes plant growth (leading to higher ∑alk<sub>long-chain</sub>). Moreover, we found that human activity significantly affected ∑alk<sub>long-chain</sub> through cultivation and grazing after 2005. Our findings may have broad significance for paleoclimate reconstruction of other hydrologically closed lakes, highlighting the importance of proxy validation studies.</p>