Combined Effects of UV Exposure Duration and Mechanical Abrasion on Fragmentation Rate and Particle Size Distrubution of Plastics

Abstract

Photo-oxidation and mechanical abrasion on beaches are thought to be major weathering andfragmentation processes for generating secondary microplastics. None of scientific informationis, however, available so far for fragmentation process of plastics. Fragmentation of top threemarine debris polymer types such as polyethylene (PE), polypropylene (PP), and expandedpolystyrene (EPS) on beach environment were simulated with UV exposure and subsequentaccelerated mechanical abrasion experiment in a laboratory. Each ten of PE, PP and EPS pelletswere exposed in a UV chamber for 0, 2, 6 and 12 months. The UV exposed polymer pellets wereseparately placed by polymer type in amber bottles with pretreated natural sand, and then rotatedwith a roller mixer for 2 month at 35 rpm. Fragmented polymer particles were extracted bydensity separation with deionized water and identified with a fluorescence microscope after NileRed staining. Only two month mechanical abrasion was enough to produce 40,000 micro-sizedparticles of EPS, while less than 100 particles of PE and PP were produced. UV exposureduration significantly affected on total number of the fragmented particles after 2 months for PPand EPS and 6 months for PE. After 12 months of UV exposure and subsequent 2 months ofmechanical abrasion produced total 105,007 particles for EPS, 67,174 for PP, and 201 for PE.The change of fragmentation rate accordingss of plastics. Fragmentation of top threemarine debris polymer types such as polyethylene (PE), polypropylene (PP), and expandedpolystyrene (EPS) on beach environment were simulated with UV exposure and subsequentaccelerated mechanical abrasion experiment in a laboratory. Each ten of PE, PP and EPS pelletswere exposed in a UV chamber for 0, 2, 6 and 12 months. The UV exposed polymer pellets wereseparately placed by polymer type in amber bottles with pretreated natural sand, and then rotatedwith a roller mixer for 2 month at 35 rpm. Fragmented polymer particles were extracted bydensity separation with deionized water and identified with a fluorescence microscope after NileRed staining. Only two month mechanical abrasion was enough to produce 40,000 micro-sizedparticles of EPS, while less than 100 particles of PE and PP were produced. UV exposureduration significantly affected on total number of the fragmented particles after 2 months for PPand EPS and 6 months for PE. After 12 months of UV exposure and subsequent 2 months ofmechanical abrasion produced total 105,007 particles for EPS, 67,174 for PP, and 201 for PE.The change of fragmentation rate according