Multi-spectroscopic investigation of the molecular weight distribution and copper binding ability of dissolved organic matter in Dongping Lake, China

Tuantuan Fan; Xin Yao; Haoyu Ren; Feiyang Ma; Li Liu; Xiaojia Huo; Tong Lin; Haiyan Zhu; Yinghao Zhang

doi:10.1016/j.envpol.2022.118931

Multi-spectroscopic investigation of the molecular weight distribution and copper binding ability of dissolved organic matter in Dongping Lake, China

Environ Pollut. 2022 May 1:300:118931. doi: 10.1016/j.envpol.2022.118931. Epub 2022 Feb 1.

Authors

Tuantuan Fan¹, Xin Yao², Haoyu Ren³, Feiyang Ma¹, Li Liu¹, Xiaojia Huo¹, Tong Lin¹, Haiyan Zhu¹, Yinghao Zhang¹

Affiliations

¹ School of Geography and Environment, University of Liaocheng, Liaocheng, 252000, China.
² 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. Electronic address: yaoxin@lcu.edu.cn.
³ College of Water Sciences, Beijing Normal University, Beijing, 100875, China.

PMID: 35121017
DOI: 10.1016/j.envpol.2022.118931

Abstract

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 (Cu²⁺) 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 Cu²⁺ regardless of sample type (215 nm > 285 nm > 310-360 nm). The Cu²⁺ 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 Cu²⁺ than humic-like components (logK_a: C4 > C1 > C2) in PDOM irrespective of MW. Humic-like components with MW < 500 kDa displayed higher binding potentials for Cu²⁺. 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.

Keywords: 2D-COS; Dissolved organic matter (DOM); FTIR; Metal binding; PARAFAC.

MeSH terms

Copper* / analysis
Dissolved Organic Matter
Factor Analysis, Statistical
Humans
Humic Substances / analysis
Lakes* / chemistry
Molecular Weight
Spectrometry, Fluorescence

Substances

Dissolved Organic Matter
Humic Substances
Copper