Molecular chemodiversity of dissolved organic matters released by hydrophyte decay: Implications for carbon cycling...

As an important endogenous pollutant, the release of hydrophyte-derived dissolved organic matter (HDOM) significantly increases in eutrophication of water bodies, leading to deterioration of water quality, and posing a threat to ecological environment safety. However, little is known about the molecular composition of HDOM released from the decay of hydrophytes. This work aimed to reveal the release patterns of dissolved organic carbon and dissolved inorganic carbon from four hydrophytes. The further fingerprint characteristics and molecular compositions of the HDOM were analyzed using FT-ICR-MS and UPLC-QTOF-MS. The results revealed that the CHO formula was the major molecular component of HDOM. Based on biochemical categories, the sum of lignins, lipids, and proteins in HDOM was about 80%. Recalcitrant DOM and labile DOM accounted for 62% and 38% of the HDOM, respectively. The difficulty in degrading HDOM was mainly attributed to the recalcitrance of compounds with the CHON formula in lignin. A total of 18 types of organic pollutants were identified using UPLC-QTOF-MS, lipids and lipid-like, organoheterocyclic, and benzenoid compounds accounted for 25, 20, and 19% of HDOM, respectively. In ESI+ and ESI- modes, 170, 235, 175, 420 and 63, 93, 82, 186 organic pollutants were identified in the HDOM from Coontail, Eurasian watermilfoil, Yellow floating-heart, and Lotus, respectively. This research will serve the exploration of potential mechanisms of lake eutrophication and the governance of organic pollutants in the aquatic environment.