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The influence of microplastic and nanoparticles of environmental interest on the H2O2-KSCN-CuSO4-NaOH oscillator-implications for ecotoxicology

Author(s): Christian Gagnon, PhD and Patrice Turcotte, MSc

Background: In a context where emerging exotic chemicals of commercial interest are being produced by industry, understanding the fundamental properties of these compounds is important for environmental risk assessment. Aim: We used the H2O2-KSCN-CuSO4-NaOH oscillator in the presence of luminol to explore the effects of 5 nanoparticles (nCeO2, nZnO, nCuZnFeO, nSmO and citrate-coated quantum dots) and a microplastic polyethylene bead on cyclic redox behavior in luminescence. Methods: The oscillatory changes, indicators of contaminant interactions and associated regulation, were first examined in the presence of increasing concentrations of an antioxidant (electron donor), ascorbic acid, and an oxidant (electron acceptor), Ce(IV). The oscillator was then exposed to increasing concentrations of the 5 nanoparticles and microplastic beads for 15 min at room temperature and the resulting effects on the cyclic behavior of the oscillator were examined by Fourier transformation. Results: In control conditions, the batch reaction produced 4 cyclic pulses of luminescence of 3.-6 min over a period of 15 min. Fourier transformation of the luminescence data revealed 2 major frequencies at 0.07 and 0.28, corresponding to periods of 14 and 3.6 min, respectively. The addition of the antioxidant ascorbic acid decreased the intensity of frequency 0.28, while the oxidant Ce(IV) produced luminescent changes at higher frequencies (0.43 and 0.5). It was observed that most of the tested compounds behaved like the oxidant Ce(IV), with the exception of citrate-coated quantum dots and CuZnFeO. A significant correlation was observed between the antioxidant potential (determined by the reduction of the phosphomolybdate complex) and the intensity of frequency 0.28 (r=0.77; p<0.05). Conclusion: The appearance of signals at higher frequencies was also found in more complex biological systems, such as NADH changes in yeast cells exposed to oxidant compounds, which suggests that a chemical redox oscillator behaves similarly to a biochemical redox oscillator and can serve as a proxy to understand the influence of novel chemicals on redox oscillators.

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