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Interactions of metal oxide nanoparticles with extracellular polymeric substances (EPS) of algal aggregates in an eutrophic ecosystem
- Xu, Huacheng, Pan, Jizheng, Zhang, Houhu, Yang, Liuyan
- Ecological engineering 2016 v.94 pp. 464-470
- algae, aquatic ecosystems, binding capacity, eutrophication, fluorescence, ligands, nanoparticles, spectroscopy, titration, toxicity
- Nanoparticle binding with organic ligands in natural waters is important to understand their environmental behavior and fate. In this study, the interaction of two metal oxide nanoparticles (nano-CuO and nano-Fe3O4) with extracellular polymeric substances (EPS) from algal aggregates was studied through using fluorescence emission-excitation matrix (EEM) quenching titration combined with parallel factor (PARAFAC) analysis. Spectroscopy analysis detected two protein-like peaks in the loosely bound EPS (LB–EPS) fraction, while both protein-, fulvic- and humic-like peaks can be found in the tightly bound EPS (TB–EPS) fraction. PARAFAC analysis identified three independent fluorescence components, including one tryptophan-, one tyrosine- and one humic-like component, from 68 original EEM spectra. A quenching experiment showed that humic-like components in the TB–EPS fraction exhibited higher nanoparticle binding capacities (logKM>6.23) than that in the LB–EPS fraction (logKM: <5.72), while tryptophan-like components were characterized with a high nano-CuO affinity in the LB–EPS fraction (logKM: 5.66). Further analysis revealed that the LB–EPS fraction was responsible for the transportation of nano-CuO (logKM>5.66), while the mobility of nano-Fe3O4 would be influenced by organic ligands in the TB–EPS fraction (logKM>6.28). Based on the results, the toxicity of nanoparticles in the eutrophic waters would be higher than those in the oligotrophic ecosystems. This study facilitates a deeper understanding of the environmental behavior and fate of metal oxide nanoparticles in eutrophic aquatic ecosystems.