摘要：Dissolved organic matter (DOM) is an essential component of the global carbon cycle, and estuaries link the rivers and the oceans, thus playing important roles in land-ocean DOM transformation and transport. However, the effects of hypoxia on DOM transport and fate in estuaries and coastal oceans remains poorly understood. To address this gap, we characterized the molecular composition of DOM in bottom water (BW) and sediment porewater (PW) at hypoxic and non-hypoxic sites in the Yangtze River Estuary (YRE) using ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry. Our results showed significant differences in DOM molecular composition between hypoxic and non-hypoxic areas for both BW and PW. Specifically, DOM in hypoxic sites was more recalcitrant than that in non-hypoxic areas for both BW and PW, with lower H/C, and higher O/C, double bond equivalent, and modified aromaticity index. The presence of higher polyphenols, and black carbon in hypoxic areas suggested that hypoxic conditions could facilitate the preservation of terrestrial organic matter. Furthermore, we identified a much higher number of hypoxia-unique formulas than ocean-non- hypoxia-unique formulas, indicating that hypoxia could diversify the DOM pool. Within hypoxia-unique for-mulas for PW, both biologically labile (unsaturated aliphatic compounds and peptides) and recalcitrant formulas (carboxyl-rich alicyclic molecules) were found, suggesting that hypoxia could facilitate the preservation of labile formulas and the production of recalcitrant formulas. In addition, we formulated that the sulfurization is more important in PW than BW in hypoxic areas based on the higher dissolved organic sulfur (DOS) abundance and larger number of hypoxia-only formulas in hypoxic PW, and also the precursor analysis results. Overall, our study provides insights into the effect of hypoxia on the molecular characteristics and preservation of DOM in estuaries and coastal oceans, highlighting the importance of considering hypoxia in understanding the biogeochemical processes of these ecosystems.

关键字：Dissolved organic matter; Hypoxia; Yangtze River Estuary; Molecular composition; Sulfurization

ISSN号：0048-9697

卷、期、页：卷906

发表日期：2024-01-01

期刊分区（SCI为中科院分区）：一区

收录情况：SCI（科学引文索引印刷版）,EI（工程索引）,SCIE（科学引文索引网络版）

发表期刊名称：SCIENCE OF THE TOTAL ENVIRONMENT

参与作者：李朋辉,梁文钊,周玉萍,易沅壁,何丁

第一作者：何晨,史权

论文类型：期刊论文

论文概要：李朋辉,梁文钊,周玉萍,易沅壁,何晨,史权,何丁，Hypoxia diversifies molecular composition of dissolved organic matter and enhances preservation of terrestrial organic carbon in the Yangtze River Estuary，SCIENCE OF THE TOTAL ENVIRONMENT，2024，卷906

论文题目：Hypoxia diversifies molecular composition of dissolved organic matter and enhances preservation of terrestrial organic carbon in the Yangtze River Estuary