Revealing the mobilization and age of estuarine dissolved organic matter during floods using radiocarbon and molecular fingerprints

Zhao Liang Chen; Yuanbi Yi; Ruanhong Cai; Zhe-Xuan Zhang; Wenzhao Liang; Wenjing Fu; Penghui Li; Kai Wang; Lixin Zhang; Kejun Dong; Si-Liang Li; Sheng Xu; Ding He

doi:10.1016/j.watres.2024.122898

Revealing the mobilization and age of estuarine dissolved organic matter during floods using radiocarbon and molecular fingerprints

Water Res. 2024 Nov 30:271:122898. doi: 10.1016/j.watres.2024.122898. Online ahead of print.

Authors

Zhao Liang Chen¹, Yuanbi Yi², Ruanhong Cai¹, Zhe-Xuan Zhang¹, Wenzhao Liang¹, Wenjing Fu³, Penghui Li⁴, Kai Wang⁵, Lixin Zhang⁶, Kejun Dong⁶, Si-Liang Li⁶, Sheng Xu⁶, Ding He⁷

Affiliations

¹ Department of Ocean Science and Center for Ocean Research in Hong Kong and Macau, The Hong Kong University of Science and Technology, Clear Water Bay, New Territories, Hong Kong, 999077, China.
² Department of Ocean Science and Center for Ocean Research in Hong Kong and Macau, The Hong Kong University of Science and Technology, Clear Water Bay, New Territories, Hong Kong, 999077, China. Electronic address: yuanbiyi@ust.hk.
³ Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology, Ocean University of China, Qingdao, 266100, China.
⁴ School of Marine Sciences, Sun Yat-Sen University, Zhuhai, 519082, China; Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519080, China.
⁵ Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, China.
⁶ Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin, 300072, China.
⁷ Department of Ocean Science and Center for Ocean Research in Hong Kong and Macau, The Hong Kong University of Science and Technology, Clear Water Bay, New Territories, Hong Kong, 999077, China; State Key Laboratory of Marine Pollution, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, 999077, China. Electronic address: dinghe@ust.hk.

PMID: 39642794
DOI: 10.1016/j.watres.2024.122898

Abstract

Estuaries significantly affect the transport of dissolved organic matter (DOM) from land to ocean. While the transport and composition of estuarine DOM have been extensively studied, the direct link between DOM chemistry and its age remains unclear, limiting a comprehensive understanding of the dynamics and fate of estuarine DOM under severe conditions (e.g., floods). This study applied radiocarbon and ultrahigh-resolution mass spectrometry analysis to investigate the correlation between DOM chemistry and apparent radiocarbon age of 102 samples collected from the Yangtze River Estuary during both non-flood and flood periods. The results showed that young estuarine DOM are characterized by low-molecular-weight, unsaturated molecules, while aged estuarine DOM are relatively saturated with high-molecular-weight molecules. Phosphorus and nitrogen-containing compounds were key to DOM aging, potentially increasing the lability of aged DOM. Floods significantly impact DOM by introducing more labile aged DOM and young terrestrial DOM. Furthermore, floods enhanced the flux of aged DOM transported to the East China Sea by approximately 1.4 times. Our findings contribute to the study of estuarine DOM and its response during severe floods. Additionally, incorporating apparent radiocarbon age evidence improves the understanding of terrigenous DOM and its fate in large river estuaries before it contributes to the ocean carbon reservoir.

Keywords: Dissolved organic matter; FT-ICR MS; Flood; Radiocarbon; Yangtze River estuary.