Environmental concentration PFOS as a light shield for lake exopolymers against photodegradation by formation of sandwiched supramolecular nanostructures

EPS (exopolymers) play a central role in global carbon cycling due to huger amount in aquatic environment, and PFOS (Perfluorooctane sulfonate) is also ubiquitous and persistent pollutant. Whether and how can PFOS of environmental concentrations affect behavior and fate of EPS was unclear. In this study, for the first time interaction between lake EPS and PFOS of environmental concentrations was visually probed by AFM-IR tech-nique. It was found that EPS could effectively trap PFOS and the latter of environmental concentrations could trigger nanoscale reassembly of the former. Sandwiched PFOS-EPS nanostructures were formed via supramo-lecular interaction between EPS and PFOS, confirmed by fluorescence quenching titration and FTIR spectros-copy. The PFOS microlayers sandwiched in EPS was proven to be a light shield that could protect EPS from photodegradation because of its high reflectivity and nearly zero absorbance of UV-Vis light. The light shielding effect of PFOS was confirmed by evidences from photodegradation experiments, including change of concen-trations of ions released and molecular weight distribution patterns. These novel findings provided valuable information for deep insight into environmental behavior of PFOS and its effects on biogeochemical carbon cycle of biopolymers in global waters.

Automated summary

In this study, the interaction between lake EPS and PFOS of environmental concentrations was observed using AFM-IR technique for the first time. It was found that EPS could effectively trap PFOS and trigger nanoscale reassembly. The sandwiched PFOS-EPS nanostructures acted as a light shield to protect EPS from photodegradation.