Interactions between dissolved organic matter with different molecular weights and nonylphenol in surface water bodies

Dissolved organic matter (DOM) has a complex composition, which can interact with various pollutants and affect the removal of pollutants. Therefore, a thorough understanding of the interaction between the encccvironmental hormone nonylphenol (NP) and DOM is crucial for environmental impact and development. In this study, the interaction was investigated by means of excitation emission matrix (EEM) fluorescence spectroscopy, UV–Vis spectroscopy, FT-IR spectroscopy, nuclear magnetic resonance (NMR) and complex model analysis. The interaction between different MW DOM and NP was verified by the spectral characterization data. According to the characterization analysis, the main components of DOM in water samples were proteinoid (C1, C2, C4) with MW < 1 k Da, and their binding capacity (log K_a value) and binding site number (n) showed the maximum values (3.37, 3.24, 3.26; 0.81, 1.22, 0.52). For the humus like substance (C3) with larger molecular weight, the log K_a value and the number of binding points n increased with increasing molecular weight, and the maximum values were 3.13 and 0.31, respectively. It can be seen that low molecular weight proteins have strong binding ability and binding sites with NP, and high molecular weight humus also have strong binding ability. Overall, the interaction between DOM and NP has molecular weight dependence and heterogeneity. The purpose of this study is to deeply understand the interaction characteristics of different MW DOM with NP, and to provide theoretical support and reference for the study of the removal effects of NP pollutants.