Fig. 2: Weathering-induced changes in surface chemistry and hydration structure on microplastics (MPs).
From: Weathering influences the ice nucleation activity of microplastics
a–c Three-dimensional (3D) surface plots generated using atomic force microscopy (AFM) data for the polyethylene (PE) MPs which are weathered for 0, 10 and 180 days. d X-ray photoelectron spectroscopy (XPS) spectra of PE MPs weathered for 0, 10, and 180 days. The emerging peaks fall within the O 1 s region of the XPS spectra. e Change in the height profile of the PE MPs with increasing weathering time. f The average (left y-axis) and maximum (right y-axis) height of the roughness profile of the PE MP surface as a function of weathering time. The black squares represent the average surface roughness (left y-axis) and the green circles represent the maximum height of the surface roughness (right y-axis). The error bars represent the standard error. g-i Slices of the force gradient map normal to the PE plastic surface at (g) Day 0, (h) Day 5 and (i) Day 10 of accelerated weathering. The force gradient map suggests local ordering of the water molecules at the weathered plastic surface (indicated by the arrows). j Average force gradient curves for PE weathered for 0, 5 and 10 days extracted from 3D AFM data. The data reported in (g–j) was obtained for PE sheets instead of MPs, because of the need for smooth surface for identifying the hydration structure using 3D AFM. Source data are provided as a Source Data file.
