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Yin S, Liu Y, Wei C, Zhu D. Comparing molecular signatures of dissolved organic matter (DOM) in four large freshwater lakes differing in hydrological connectivity to the Changjiang River. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 946:174401. [PMID: 38964414 DOI: 10.1016/j.scitotenv.2024.174401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Revised: 06/28/2024] [Accepted: 06/29/2024] [Indexed: 07/06/2024]
Abstract
Freshwater lakes serve as active conduits for processing terrestrial dissolved organic matter (DOM), playing a crucial role in global carbon cycle. Little attention has been paid to how hydrological connectivity to a large river would affect the molecular signatures of DOM in lakes. Here, we systematically characterized and compared the molecular signatures of DOM in surface waters of four large freshwater lakes in the middle and lower Changjiang River basin that are directly connected to the river (Lake Dongting and Lake Poyang, referred to as Lakeconnected) or indirectly connected to the river (Lake Chao and Lake Tai, referred to as Lakenonconnected). The DOM in Lakeconnected was found to have similar total organic carbon (TOC)-normalized contents and characteristics of lignin phenols to the DOM in surface waters from the upstream Changjiang river, indicating allochthonous/terrestrial sources from riverine inputs. As indicated by the UV-vis and fluorescence analyses, the DOM in Lakeconnected overall had higher aromaticity and larger average molecular weight as well as stronger allochthonous feature compared to the DOM in Lakenonconnected. Consistently, the FT-ICR MS analysis revealed that the DOM in Lakeconnected had higher molecular diversity, higher unsaturation degree, and larger proportions of highly aromatic compounds. In contrast, the DOM in Lakenonconnected had larger proportions of lipids and peptide-like structures, but lower proportions of aromatic compounds, which could be ascribed to the enhanced autochthonous production and photodegradation due to pollution and eutrophication as well as longer water residence time. The results highlight the strong impacts of the hydrological connectivity to a large river on the molecular signatures of lake DOM. CAPSULE: The hydrological connectivity of the lakes to the Changjiang River has strong impacts on the molecular signatures of lake DOM.
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Affiliation(s)
- Shujun Yin
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Yafang Liu
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Chenhui Wei
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China
| | - Dongqiang Zhu
- School of Urban and Environmental Sciences, Key Laboratory of the Ministry of Education for Earth Surface Processes, Peking University, Beijing 100871, China.
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Liu J, Wang C, Zhou J, Dong K, Elsamadony M, Xu Y, Fujii M, Wei Y, Wang D. Thermodynamics and explainable machine learning assist in interpreting biodegradability of dissolved organic matter in sludge anaerobic digestion with thermal hydrolysis. BIORESOURCE TECHNOLOGY 2024; 412:131382. [PMID: 39214181 DOI: 10.1016/j.biortech.2024.131382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2024] [Revised: 08/26/2024] [Accepted: 08/27/2024] [Indexed: 09/04/2024]
Abstract
Dissolved organic matter (DOM) is essential in biological treatment, yet its specific roles remain incompletely understood. This study introduces a machine learning (ML) framework to interpret DOM biodegradability in the anaerobic digestion (AD) of sludge, incorporating a thermodynamic indicator (λ). Ensemble models such as Xgboost and LightGBM achieved high accuracy (training: 0.90-0.98; testing: 0.75-0.85). The explainability of the ML models revealed that the features λ, measured m/z, nitrogen to carbon ratio (N/C), hydrogen to carbon ratio (H/C), and nominal oxidation state of carbon (NOSC) were significant formula features determining biodegradability. Shapley values further indicated that the biodegradable DOM were mostly formulas with λ lower than 0.03, measured m/z value higher than 600 Da, and N/C ratios higher than 0.2. This study suggests that a strategy based on ML and its explainability, considering formula features, particularly thermodynamic indicators, provides a novel approach for understanding and estimating the biodegradation of DOM.
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Affiliation(s)
- Jibao Liu
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, 2-12-1-M1-22 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Chenlu Wang
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Jiahui Zhou
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, 2-12-1-M1-22 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Kun Dong
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guilin 541006, China
| | - Mohamed Elsamadony
- Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia; Center for Refining and Advanced Chemicals, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia
| | - Yufeng Xu
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guilin 541006, China.
| | - Manabu Fujii
- Department of Civil and Environmental Engineering, School of Environment and Society, Tokyo Institute of Technology, 2-12-1-M1-22 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Yuansong Wei
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Dunqiu Wang
- Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guilin 541006, China
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Peng Y, Niu L, Hu Y, Huo C, Shi J, Fan Z, Yan Y, Zhang Z, Wang X. Long-term effects of nitrogen and phosphorus fertilization on profile distribution and characteristics of dissolved organic matter in fluvo-aquic soil. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 366:121834. [PMID: 39003911 DOI: 10.1016/j.jenvman.2024.121834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Revised: 07/06/2024] [Accepted: 07/09/2024] [Indexed: 07/16/2024]
Abstract
Dissolved organic matter (DOM) drives numerous biogeochemical processes (e.g. carbon cycling) in agro-ecosystems and is sensitive to fertilization management. Nevertheless, changes in the quantity and quality of DOM in the vertical soil profile following long-term continuous nitrogen (N) and phosphorus (P) inputs remain unclear. In this study, the contents and optical characteristics of DOM along a 2-m soil profile were investigated using a 40-year wheat/maize rotation combined with experiments using different N and P fertilization rates in the North China Plain. The results revealed that the dissolved organic carbon (DOC) content decreased with an increase in soil depths. Compared with that in the control (no fertilization), 40-year N, P, and N + P additions increased the soil DOC content by 26%-69%, except for 270-kg N, and 67.5-kg P treatments. N + P application resulted in higher DOC contents than N-alone and P-alone applications. N, P, and N + P inputs increased or did not affect the aromaticity and hydrophobicity of DOM at 0-40 cm but reduced them from 40 to 200 cm. Compared with that in the control, N, P, and N + P inputs enhanced the content of humic acid-like substances (C1+C2+C3+C4) and decreased the content of protein-like substance (C5). C1 was the dominant component among the five DOM, representing the microbial humic component. Optical indices also indicated that soil DOM primarily originated from microbial sources. Nutrient addition accelerated transformation between complex C1 and simple C5 via promoting microbial activities. These results imply that N and P fertilizers increased the DOM content and altered its composition, thereby potentially affecting the stability of soil organic matter in the agroe-cosystems.
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Affiliation(s)
- Yumei Peng
- Key Laboratory of Arable Land Conservation (North China), College of Land Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Lingan Niu
- Qu Zhou Experimental Station, China Agricultural University, Quzhou, Hebei, 057250, China
| | - Yalei Hu
- Key Laboratory of Arable Land Conservation (North China), College of Land Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Chunpeng Huo
- Key Laboratory of Arable Land Conservation (North China), College of Land Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Jia Shi
- Key Laboratory of Arable Land Conservation (North China), College of Land Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Zhongmin Fan
- Key Laboratory of Arable Land Conservation (North China), College of Land Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Yuxin Yan
- Key Laboratory of Arable Land Conservation (North China), College of Land Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Ziyun Zhang
- Key Laboratory of Arable Land Conservation (North China), College of Land Science and Technology, China Agricultural University, Beijing, 100193, China
| | - Xiang Wang
- Key Laboratory of Arable Land Conservation (North China), College of Land Science and Technology, China Agricultural University, Beijing, 100193, China.
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Craig A, Moodie LWK, Hawkes JA. Preparation of Simple Bicyclic Carboxylate-Rich Alicyclic Molecules for the Investigation of Dissolved Organic Matter. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:7078-7086. [PMID: 38608252 PMCID: PMC11044592 DOI: 10.1021/acs.est.4c00166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 04/03/2024] [Accepted: 04/03/2024] [Indexed: 04/14/2024]
Abstract
Dissolved organic matter (DOM) is a vast and complex chemical mixture that plays a key role in the mediation of the global carbon cycle. Fundamental understanding of the source and fate of oceanic organic matter is obscured due to poor definition of the key molecular contributors to DOM, which limits accurate sample analysis and prediction of the Earth's carbon cycle. Previous work has attempted to define the components of the DOM through a variety of chromatographic and spectral techniques. However, modern preparative and analytical methods have not isolated or unambiguously identified molecules from DOM. Therefore, previously proposed structures are based solely on the mixture's aggregate properties and do not accurately describe any true individual molecular component. In addition to this, there is a lack of appropriate analogues of the individual chemical classes within DOM, limiting the scope of experiments that probe the physical, chemical, and biological contributions from each class. To address these problems, we synthesized a series of analogues of carboxylate-rich alicyclic molecules (CRAM), a molecular class hypothesized to exist as a major contributor to DOM. Key analytical features of the synthetic CRAMs were consistent with marine DOM, supporting their suitability as chemical substitutes for CRAM. This new approach provides access to a molecular toolkit that will enable previously inaccessible experiments to test many unproven hypotheses surrounding the ever-enigmatic DOM.
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Affiliation(s)
- Alexander
J. Craig
- Analytical
Chemistry, Department of Chemistry BMC, Uppsala University, Uppsala 752 37, Sweden
- Drug
Design and Discovery, Department of Medicinal Chemistry, Uppsala University, Uppsala 752 37, Sweden
| | - Lindon W. K. Moodie
- Drug
Design and Discovery, Department of Medicinal Chemistry, Uppsala University, Uppsala 752 37, Sweden
| | - Jeffrey A. Hawkes
- Analytical
Chemistry, Department of Chemistry BMC, Uppsala University, Uppsala 752 37, Sweden
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Wen Z, Han J, Shang Y, Tao H, Fang C, Lyu L, Li S, Hou J, Liu G, Song K. Spatial variations of DOM in a diverse range of lakes across various frozen ground zones in China: Insights into molecular composition. WATER RESEARCH 2024; 252:121204. [PMID: 38301526 DOI: 10.1016/j.watres.2024.121204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2023] [Revised: 01/24/2024] [Accepted: 01/25/2024] [Indexed: 02/03/2024]
Abstract
Dissolved organic matter (DOM) plays a significant role in aquatic biogeochemical processes and the carbon cycle. As global climate warming continues, it is anticipated that the composition of DOM in lakes will be altered. This could have significant ecological and environmental implications, particularly in frozen ground zones. However, there is limited knowledge regarding the spatial variations and molecular composition of DOM in lakes within various frozen ground zones. In this study, we examined the spatial variations of in-lake DOM both quantitatively, focusing on dissolved organic carbon (DOC), and qualitatively, by evaluating optical properties and conducting molecular characterization using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Lakes in cold regions retained more organic carbon compared to those in warmer regions, the comparison of the mean value of DOC concentration of all sampling sites in the same frozen ground zone showed that the highest mean lake DOC concentration found in the permafrost zone at 21.4 ± 19.3 mg/L. We observed decreasing trends in E2:E3 and MLBL, along with increasing trends in SUVA254 and AImod, along the gradually warming ground. These trends suggest lower molecular weight, reduced aromaticity, and increased molecular lability of in-lake DOM in the permafrost zone compared to other frozen ground zones. Further FT-ICR MS characterization revealed significant molecular-level heterogeneity of DOM, with the lowest abundance of assigned DOM molecular formulas found in lakes within permafrost zones. In all studied zones, the predominant molecular formulas in-lake DOM were compounds consisted by CHO elements, accounting for 40.1 % to 63.1 % of the total. Interestingly, the percentage of CHO exhibited a gradual decline along the warming ground, while there was an increasing trend in nitrogen-containing compounds (CHON%). Meanwhile, a substantial number of polyphenols were identified, likely due to the higher rates of DOM mineralization and the transport of terrestrial DOM derived from vascular plants under the elevated temperature and precipitation conditions in the warming region. In addition, sulfur-containing compounds (CHOS and CHNOS) associated with synthetic surfactants and agal derivatives were consistently detected, and their relative abundances exhibited higher values in seasonal and short-frozen ground zones. This aligns with the increased anthropogenic disturbances to the lake's ecological environment in these two zones. This study reported the first description of in-lake DOM at the molecular level in different frozen ground zones. These findings underline that lakes in the permafrost zone serve as significant hubs for carbon processing. Investigating them may expand our understanding of carbon cycling in inland waters.
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Affiliation(s)
- Zhidan Wen
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Jiarui Han
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yingxin Shang
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Hui Tao
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Chong Fang
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Lili Lyu
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Sijia Li
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Junbin Hou
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Ge Liu
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China
| | - Kaishan Song
- Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China; School of Environment and Planning, Liaocheng University, Liaocheng 252000, China.
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