School of Geography and Environment, University of Liaocheng, Liaocheng, 252000, China.
School of Geography and Environment, University of Liaocheng, Liaocheng, 252000, China; Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
Environ Pollut. 2022 May 1;300:118931. doi: 10.1016/j.envpol.2022.118931. Epub 2022 Feb 1.
The properties and metal-binding abilities of dissolved organic matter (DOM) rely on its molecular weight (MW) structure. In this study, the spatial differences of DOM in compositions, MW structures, and binding mechanisms with copper (Cu) in Dongping Lake were investigated by applying excitation-emission matrix combining parallel factor analysis (EEM-PARAFAC), synchronous fluorescence (SF) spectra, two-dimensional correlation spectra (2D-COS), and Fourier transform infrared (FTIR) spectra. The EDOM for the entrance of the Dawen River and PDOM for the macrophyte-dominated region were divided from DOM of Dongping Lake based on hierarchical clustering analysis (HCA) and principal component analysis (PCA) and were size-fractioned into MW < 500 kDa and <100 kDa fractions. According to EEM-PARAFAC, Dongping Lake was dominated by tryptophan-like substances with MW < 500 kDa. The concentration of PDOM was higher than that of EDOM (p < 0.05). 2D-COS showed that protein-like components preceded humic-like components binding to Cu regardless of sample type (215 nm > 285 nm > 310-360 nm). The Cu binding capacity of DOM exhibited specific differences in space, components, and molecular weights. The humic-like component 1 (C1) and tryptophan-like component 4 (C4) of PDOM showed stronger binding abilities than those of EDOM. Endogenous tryptophan-like component 4 (C4) had a higher binding affinity for Cu than humic-like components (logK: C4 > C1 > C2) in PDOM irrespective of MW. Humic-like components with MW < 500 kDa displayed higher binding potentials for Cu. FTIR spectra showed that the main participants of DOM-Cu complexation included aromatic hydrocarbons, aliphatic groups, amide Ⅰ bands, and carboxyl functional groups. This study provides spatial-scale insights into the molecular weight structure of DOM in influencing the behavior, fate, and bioavailability of heavy metals in lakes.
溶解有机质（DOM）的性质和金属结合能力与其分子量（MW）结构有关。本研究通过应用激发-发射矩阵结合平行因子分析（EEM-PARAFAC）、同步荧光（SF）光谱、二维相关光谱（2D-COS）和傅里叶变换红外（FTIR）光谱，研究了东平湖 DOM 在组成、MW 结构和与铜（Cu）结合机制方面的空间差异。基于层次聚类分析（HCA）和主成分分析（PCA），将东平湖 DOM 分为入口处的 EDOM 和以大型植物为主的 PDOM，并按 MW<500 kDa 和<100 kDa 进行分级。根据 EEM-PARAFAC，东平湖以 MW<500 kDa 的色氨酸类物质为主。PDOM 的浓度高于 EDOM（p<0.05）。2D-COS 表明，无论样品类型如何（215nm>285nm>310-360nm），蛋白质类成分都先于类腐殖质成分与 Cu 结合。DOM 的 Cu 结合能力在空间、成分和分子量上表现出特异性差异。PDOM 的类腐殖质成分 1（C1）和色氨酸类成分 4（C4）比 EDOM 具有更强的结合能力。无论 MW 如何，PDOM 中内源性色氨酸类成分 4（C4）对 Cu 的结合亲和力都高于类腐殖质成分（logK：C4>C1>C2）。MW<500 kDa 的类腐殖质成分对 Cu 具有更高的结合潜力。FTIR 光谱表明，DOM-Cu 络合物的主要参与者包括芳香烃、脂肪族基团、酰胺 I 带和羧基官能团。本研究提供了关于 DOM 分子量结构影响湖泊中重金属行为、归宿和生物可利用性的空间尺度见解。
