Investigating spectroscopic and copper-binding characteristics of organic matter derived from sediments and suspended particles using EEM-PARAFAC combined with two-dimensional fluorescence/FTIR correlation analyses.

Different environmental dynamics of sediment organic matter (SOM) and suspended particulate organic matter (SPOM) result in great disparities in characteristics and subsequent interactions with heavy metals. In this study, sediments and suspended particles were collected from two large and shallow lakes (Taihu and Hongze Lake) to study the difference in the characteristics and copper binding properties between SOM and SPOM through spectroscopy method. Our results showed that SPOM in Taihu Lake was dominated by autochthonous tyrosine-like substance and SOM was dominated by terrestrial humic-like substance, whereas SPOM in Hongze Lake was dominated by terrestrial humic-like substances. Furthermore, dissolved organic matter (DOM) in Taihu and Hongze Lake was controlled by autochthonous protein and terrestrial humic substances, respectively. Comparison of SPOM between these two lakes indicated that various organic matter sources could be responsible for the organic matter characteristics in suspended particles. Meanwhile, relatively higher binding affinities and more binding sites were observed for SPOM in both two lakes compared to SOM through two-dimensional correlation spectroscopy (2D-COS) analysis of synchronous fluorescence spectra. Moreover, 2D-COS analysis of FTIR spectra revealed that hydrophobic groups (i.e., phenolic groups) had higher binding affinity than hydrophilic groups (i.e., polysaccharide groups) for both SOM and SPOM. Our results provide a new angle for understanding the suspended particles in shallow lakes, which might play a more important role in the environmental behaviors of heavy metals, than has been previously thought.