Ji Hengkuan, Wang Hua, Wu Zhipeng, Wang Dengfeng, Wang Xilong, Fu Peijiao, Li Caisheng, Deng Wangang
School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China.
Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences, Haikou 571101, China.
Sci Total Environ. 2024 Jan 15;908:168577. doi: 10.1016/j.scitotenv.2023.168577. Epub 2023 Nov 14.
Source, composition and molecular diversity determine the reactivity and stabilization of organic matter (OM, dissolved [DOM]/particulate [POM]), affecting its behavior and fate. Here, multiple spectral and mass spectrometry techniques were applied to examine how riparian land-use shaped the source, composition and molecular diversity of POM and DOM (HDOM) in adjacent headstreams. Compared to HDOM with abundant lignins, microbially-transformed heteroatoms and carboxyl-rich alicyclic acids (CRAMs), POM exhibited higher allochthonous characteristics and more bioactive components, but lower molecular weight and diversity in different land-use-dominated streams. Compared to wetland-dominated headstreams, both POM and HDOM exhibited more terrestrial origin and condensed aromatics/tannins molecules for agriculture-impacted headstreams and bio-labile lipids, proteins and carbohydrates for forest-impacted headstreams. Structural equation mode (SEM) showed that soil-derived DOM (SDOM) showed the most prominent influence on the source, composition and molecular diversity of POM and the source of HDOM. The molecular composition and diversity of HDOM were mainly influenced by soil properties/SDOM and aquatic microorganisms, respectively. Redundancy analysis (RDA) revealed that autochthonous, bio-labile compositions of POM in forest and wetland streams were positively related to aquatic Bacteroidetes/Cyanobacteria, and carbohydrates/biogenic index of SDOM, while that of HDOM were positively linked with aquatic Bacteroidetes/Cyanobacteria, and SDOM molecular diversity. Terrestrial and aromatic POM in agricultural headstreams were associated with aquatic total nitrogen/Actinobacteria, and humification degree, aromatic/phenolic substances of SDOM, while that of HDOM were mainly regulated by aquatic nitrate/total nitrogen/Actinobacteria, and aromatic/carboxylic-containing moieties of SDOM. Noteworthily, the molecular diversity of agricultural OM increased along the soil-stream continuum due to the input of soil condensed aromatics and tannins. The opposite trend was observed in forest and wetland streams due to the input of bioactive carbohydrates and the microbial-degradation in-stream. These results are helpful to predict the behavior and fate of OM and determine effective management strategies in tropical coastal regions undergoing intense anthropogenic alterations.
来源、组成和分子多样性决定了有机物质（OM，溶解态[DOM]/颗粒态[POM]）的反应活性和稳定性，影响其行为和归宿。在此，我们应用多种光谱和质谱技术，研究河岸土地利用如何塑造相邻源头溪流中POM和DOM（HDOM）的来源、组成和分子多样性。与富含木质素、经微生物转化的杂原子和富含羧基的脂环酸（CRAMs）的HDOM相比，POM在不同土地利用主导的溪流中表现出更高的外源特征和更多生物活性成分，但分子量和多样性较低。与以湿地为主的源头溪流相比，对于受农业影响的源头溪流，POM和HDOM均表现出更多的陆地来源和缩合芳烃/单宁分子；对于受森林影响的源头溪流，POM和HDOM则表现出更多生物易降解的脂质、蛋白质和碳水化合物。结构方程模型（SEM）表明，土壤源DOM（SDOM）对POM的来源、组成和分子多样性以及HDOM的来源影响最为显著。HDOM的分子组成和多样性分别主要受土壤性质/SDOM和水生微生物的影响。冗余分析（RDA）表明，森林和湿地溪流中POM的自生、生物易降解成分与水生拟杆菌属/蓝细菌以及SDOM的碳水化合物/生源指数呈正相关，而HDOM的自生、生物易降解成分与水生拟杆菌属/蓝细菌以及SDOM的分子多样性呈正相关。农业源头溪流中的陆地和芳香族POM与水生总氮/放线菌以及SDOM的腐殖化程度、芳香族/酚类物质有关，而HDOM的陆地和芳香族POM主要受水生硝酸盐/总氮/放线菌以及SDOM的芳香族/含羧基部分的调节。值得注意的是，由于土壤缩合芳烃和单宁的输入，农业有机物质的分子多样性沿土壤 - 溪流连续体增加。由于生物活性碳水化合物的输入和溪流中的微生物降解，在森林和湿地溪流中观察到相反的趋势。这些结果有助于预测有机物质的行为和归宿，并确定在经历强烈人为改变的热带沿海地区的有效管理策略。
