Complexation of copper algaecide and algal organic matter in algae-laden water: Insights into complex metal-organic interactions.

Copper-based algicides have been widely used to suppress algae blooms; however, the release of algal organic matter (AOM) on account of cell lysis may cause significant changes in the mitigation, transformation, and bioavailability of Cu(II). In the present work, the binding characteristics of Cu(II) with AOM were explored via combinative characterization methods, such as high-performance size exclusion chromatography, differential absorption spectra analysis, and joint applications of two-dimensional correlation spectroscopy (2D-COS), as well as heterospectral 2D-COS and moving window 2D-COS analyses of UV, synchronous fluorescence, and FTIR spectra. Carboxyl groups displayed a preferential interaction to Cu(II) binding, followed by polysaccharides. The spectral changes of C]O stretching occur after the change of chromophores in complexation with Cu(II). The AOM chromophores exhibit obvious conformations at Cu(II) concentrations higher than 120 μM, while AOM fluorophores and functional groups exhibit the greatest changes at Cu(II) concentrations lower than 20 μM. All these observations have verified the presence of binding heterogeneity and indicate that AOM could interact with Cu(II) through diverse functional moieties. Therefore, our study contributes to the better understanding of the fate of Cu(II)-AOM complexes in aquatic systems.