Fragmentation of plastics by accelerated chemical and physical weathering

Abstract

Photo-oxidation and mechanical abrasion are thought to be major weathering andfragmentation processes for generating secondary microplastics. None of scientificinformation is, however, available so far for fragmentation process of plastics.Fragmentation of polyethylene (PE), polypropylene (PP), and expanded polystyrene (EPS)on beach environment was simulated with UV exposure and subsequent mechanicalabrasion in laboratory accelerated experiments. Each ten of PE, PPand EPS pellets wereexposed to UV in a chamber for 0, 2, 6 and 12 months. The non-UV exposed (UV0) andUV exposed polymer pellets (UV2, 6 and 12) were separately placed by polymer type asthree replicates in amber bottles with pre-treated natural sand, and then rotated with aroller mixer at 36-38 rpm for 2 months. Fragmented polymer particles were extracted bydensity separation with deionized water and identified with a fluorescence microscope afterNile Red staining. Only two month mechanical abrasion was enough to produce 40,000micro-sized particles of EPS, while less than 100 particles of PE and PP were produced.UV exposure duration significantly affected on total number of the fragmented particlesafter 6 months for EPS and 12 months for PE and PP. the mean (±SD) number ofparticles produced per bottle after 12 months of UV exposure and subsequent 2 months ofmechanical abrasion were 105,008±17,182 for EPS, 60,841±10,605 foics.Fragmentation of polyethylene (PE), polypropylene (PP), and expanded polystyrene (EPS)on beach environment was simulated with UV exposure and subsequent mechanicalabrasion in laboratory accelerated experiments. Each ten of PE, PPand EPS pellets wereexposed to UV in a chamber for 0, 2, 6 and 12 months. The non-UV exposed (UV0) andUV exposed polymer pellets (UV2, 6 and 12) were separately placed by polymer type asthree replicates in amber bottles with pre-treated natural sand, and then rotated with aroller mixer at 36-38 rpm for 2 months. Fragmented polymer particles were extracted bydensity separation with deionized water and identified with a fluorescence microscope afterNile Red staining. Only two month mechanical abrasion was enough to produce 40,000micro-sized particles of EPS, while less than 100 particles of PE and PP were produced.UV exposure duration significantly affected on total number of the fragmented particlesafter 6 months for EPS and 12 months for PE and PP. the mean (±SD) number ofparticles produced per bottle after 12 months of UV exposure and subsequent 2 months ofmechanical abrasion were 105,008±17,182 for EPS, 60,841±10,605 fo