Seasonal studies of aquatic humic substances from Amazon rivers: characterization and interaction with Cu (II), Fe (II), and Al (III) using EEM-PARAFAC and 2D FTIR correlation analyses

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Constantino, Isabela Carreira ; Bento, Lucas Raimundo ; Santos, Vinicius Sarracini ; da Silva, Leila Soares ; Tadini, Amanda Maria ; Mounier, Stephane ; Piccolo, Alessandro ; Spaccini, Riccardo ; Cornelio, Marinonio Lopes ; Paschoal, Fabiana Maria Monteiro ; Sargentini Junior, Ezio ; Moreira, Altair Benedito ; Bisinoti, Marcia Cristina

• Document type: Journal article
• Source: ENVIRONMENTAL MONITORING AND ASSESSMENT; v. 196, n. 7, p. 17-pg., 2024-07-01.

Abstract

Aquatic humic substances (AHS) are defined as an important components of organic matter, being composed as small molecules in a supramolecular structure and can interact with metallic ions, thereby altering the bioavailability of these species. To better understand this behavior, AHS were extracted and characterized from Negro River, located near Manaus city and Car & uacute; River, that is situated in Itacoatiara city, an area experiencing increasing anthropogenic actions; both were characterized as blackwater rivers. The AHS were characterized by C-13 nuclear magnetic ressonance and thermochemolysis GC-MS to obtain structural characteristics. Interaction studies with Cu (II), Al (III), and Fe (III) were investigated using fluorescence spectroscopy applied to parallel factor analysis (PARAFAC) and two-dimensional correlation spectroscopy with Fourier transform infrared spectroscopy (2D-COS FTIR). The AHS from dry season had more aromatic fractions not derived from lignin and had higher content of alkyls moities from microbial sources and vegetal tissues of autochthonous origin, while AHS isolated in the rainy season showed more metals in its molecular architecture, lignin units, and polysacharide structures. The study showed that AHS composition from rainy season were able to interact with Al (III), Fe (III), and Cu (II). Two fluorescent components were identified as responsible for interaction: C1 (blue-shifted) and C2 (red-shifted). C1 showed higher complexation capacities but with lower complexation stability constants (K-ML ranged from 0.3 to 7.9 x 10(5)) than C2 (K-ML ranged from 3.1 to 10.0 x 10(5)). 2D-COS FTIR showed that the COO- and C-O in phenolic were the most important functional groups for interaction with studied metallic ions. (AU)

• FAPESP's process: 17/05575-2 - Structural similarity of the humic substances from hydrochar obtained from vinasse and sugarcane bagasse with the Black Earth (TPI)
• Grantee: Lucas Raimundo Bento
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 15/22954-1 - Metal transportation and natural organic matter characterization from rivers of Itacoatiara, Amazônia
• Grantee: Márcia Cristina Bisinoti
• Support Opportunities: Regular Research Grants
• FAPESP's process: 17/17991-0 - Molecular characterization of the humic substances from "Terra Preta de Indio" soils and hydrochar from sugarcane wastes" by Humeomics
• Grantee: Lucas Raimundo Bento
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree