Potential retention of dissolved organic matter by soil minerals during wetland water-table fluctuations.

Autor: Wang S; State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China; China National Botanical Garden, Beijing 100093, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China; National Engineering Laboratory for Site Remediation Technologies, Beijing Construction Engineering Group Environmental Remediation Co. Ltd., Beijing 100015, PR China., Liu T; State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China; China National Botanical Garden, Beijing 100093, PR China. Electronic address: tingliu@ibcas.ac.cn., Zhu E; State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China; China National Botanical Garden, Beijing 100093, PR China., He C; State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, PR China., Shi Q; State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, PR China., Feng X; State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China; China National Botanical Garden, Beijing 100093, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China. Electronic address: xfeng@ibcas.ac.cn.
Jazyk: angličtina
Zdroj: Water research [Water Res] 2024 May 01; Vol. 254, pp. 121412. Date of Electronic Publication: 2024 Mar 03.
DOI: 10.1016/j.watres.2024.121412
Abstrakt: Wetlands export large amounts of dissolved organic carbon (DOC) downstream, which is sensitive to water-table fluctuations (WTFs). While numerous studies have shown that WTFs may decrease wetland DOC via enhancing DOC biodegradation, an alternative pathway, i.e., retention of dissolved organic matter (DOM) by soil minerals, remains under-investigated. Here, we conducted a water-table manipulation experiment on intact soil columns collected from three wetlands with varying contents of reactive metals and clay to examine the potential retention of DOM by soil minerals during WTFs. Using batch sorption experiments and Fourier transform ion cyclotron resonance mass spectrometry, we showed that mineral (bentonite) sorption mainly retained lignin-, aromatic- and humic-like compounds (i.e., adsorbable compounds), in contrast to the preferential removal of protein- and carbohydrate-like compounds during biodegradation. Seven cycles of WTFs significantly decreased the intensity of adsorbable compounds in DOM (by 50 ± 21% based on fluorescence spectroscopy) and DOC adsorbability (by 2-20% and 1.9-12.7 mg L -1 based on batch sorption experiment), to a comparable extent compared with biodegradable compounds (by 11-32% and 1.6-15.2 mg L -1 ). Furthermore, oxidation of soil ferrous iron [Fe(II)] exerted a major control on the magnitude of potential DOM retention by minerals, while WTFs increased mineral-bound lignin phenols in the Zoige soil with the highest content of lignin phenols and Fe(II). Collectively, these results suggest that DOM retention by minerals likely played an important role in DOC decrease during WTFs, especially in soils with high contents of oxidizable Fe. Our findings support the 'iron gate' mechanism of soil carbon protection by newly-formed Fe (hydr)oxides during water-table decline, and highlight an underappreciated process (mineral-DOM interaction) leading to contrasting fate (i.e., preservation) of DOC in wetlands compared to biodegradation. Mineral retention of wetland DOC hence deserves more attention under changing climate and human activities.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Databáze: MEDLINE
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