Vertical Binding Characteristics Between Dissolved Organic Matter and Heavy Metals in the Upper Reaches of the Yangtze River Using EEM-PARAFAC and 2D-FTIR-COS
2025
Xihuan Wang | Tiansen Zou | Weibo Zhang | Yili Fan | Yingchen Bai
Dissolved organic matter (DOM) exerts a significant influence on the environmental behavior of heavy metals in water. This study investigated the spatial distribution characteristics of DOM in the upper reaches of the Yangtze River and its vertical (0&ndash:10 m) binding behavior with heavy metals. The results indicated that humic acid-like substances dominated the DOM composition in the river water, exhibiting spatial variability horizontally, with a higher proportion of protein-like components observed at the depth of 8 m. The DOM showed complexation affinity (LogK) values were 4.71&ndash:6.38 for Cu2+ and 4.27&ndash:6.26 for Hg2+, with the protein-like component C3 exhibiting higher LogK values when binding with Cu2+ or Hg2+ compared to humic-like components. The LogKCu and LogKHg varied distinctly with water depth, and at 8 m depth, humus-like component C1 exhibited stronger binding affinity for Hg2+, whereas protein-like component C3 showed greater affinity for Cu2+. The 2D-FTIR-COS analysis revealed that, in the DOM-Cu complexes, DOM from surface water preferentially bound to O-H groups of carbohydrates, phenols, and carboxylic acids, while deep water DOM favored C=O groups in amides: for DOM&ndash:Hg complexes, the active binding sites varied distinctly with depth. This study provides novel insights into the migration and transformation mechanisms of heavy metals in rivers.
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