Heterogeneity of molecular-level and photochemical of dissolved organic matter derived from decomposing submerged macrophyte and algae. (15th May 2023)

• Record Type: Journal Article
• Authors: He, Jia; Jiao, Lixin; Zhi, Guoqiang; Wu, Xue; Yang, Yan; Ding, Shuai; Zheng, Jinlong; Shao, Zhi; Xia, Rui
• Is Part Of: Journal of environmental management. Volume 334(2023)
• Publication Date: 2023-05-15
• Subjects: Dissolved organic matter (DOM) -- Fourier-transform ion cyclotron resonance mass spectrometry -- Photochemical heterogeneity -- Submerged macrophyte and algae; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2023.117420
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Aquatic macrophytes and algae are the most important sources of autochthonous dissolved organic matter (DOM), and their transformation and reuse significantly affect aquatic ecosystem health. In this study, Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) was used to identify the molecular features between submerged macrophyte-derived DOM (SMDOM) and algae-derived DOM (ADOM). The photochemical heterogeneity between SMDOM and ADOM by UV254 -irradiation and their molecular mechanism were also discussed. The results showed that the molecular abundance of SMDOM was dominated by lignin/CRAM-like structures, tannins, and concentrated aromatic structures (sum of 91.79%), while that of ADOM was dominated by lipids, proteins, and unsaturated hydrocarbons (sum of 60.30%). UV254 -radiation resulted in a net reduction of tyrosine-like, tryptophan-like and terrestrial humic-like, and conversely a net production of marine humic-like. The light decay rate constants obtained by the multiple exponential function model fitting revealed that both tyrosine-like and tryptophan-like components of SMDOM could be rapidly and directly photodegraded, while the photodegradation of tryptophan-like in ADOM depended on the production of photosensitizers. The photo-refractory fractions of both SMDOM and ADOM were as follows: humic-like > tyrosine-like > tryptophan-like. Our results provide new insights into the fate of autochthonous DOM in aquatic ecosystems where "grass-algae" coexist or evolve. Highlights: Significant differences at the molecular level between SMDOM and ADOM. SMDOM is more photolabile than ADOM. The rapid photodegradation of SMDOM is attributed to abundant tannins. Photodegradation of tryptophan-like in ADOM depends on photosensitizer production.