Release of secondary microplastics and additives from polymer pellets exposed to artificial sunlight and aquatic environment

Within the framework of this study, the degradation of six commercially available types of polymer pellets was systematically monitored after long-term exposure to artificial sunlight and aquatic environment. The ABS, HDPE (non-processed, recycled), PA+GF30 and PA6 were placed in the demineralized water and stored under the UV lighting for the period of 18 months. Simultaneously, selected polymer grains were exposed to UV radiation only. Changes of the surface topography and physico-chemical properties were examined with the use of digital microscope, thermogravimetric (TGA) analysis and Raman spectroscopy. Release of secondary microplastics (MPs) into the water was studied by the µ-FTIR analyses. Additionally, leaching of the additives/plasticizers was monitored with the use of GC-MS technique. The long-term exposure to both degradation factors (UV+water and UV separately) generates extensive cracking on the polymer surface. However, the smoothing of the polymer surface proceeds more rapidly when UV radiation is only applied. The distribution of TGA curves and Raman spectra suggests that the UV radiation and water influence the physicochemical properties of the studied polymers. Secondary MPs were detected in water samples after 18 months of exposure to both degradation factors, with particle size ranging from 17 to 870 µm. Significant concentrations of phthalates were detected in the studied water samples, showing that UV-radiation is a key factor, activating the release of these additives from the polymer surface.