In his study, Jonathan examined how plastic in packaging for chocolate cookies, cigarett stubs, lids from take-away mugs, plastic bags and PET bottles degraded when exposed to UV light. Different long exposure times were investigated as was the issue if there was any difference in degradation if the plastic was in the water or if the materials were dry at the time of exposure.
The results showed that exposure to UV light accelerated the degradation of the plastic materials, even for short exposure times. The different materials decomposed to different extents. The fragmentation of the materials into smaller particles was generally greater in air which was explained by the fact that air is a more oxidizing environment than water. For some of the tests, it turned out that the lower analysis limit of 4 µm limited the possibilities for interpreting the results. Probably, over time, a lot of microplastic fragments were formed that were smaller than 4 µm and thus could no longer be detected with the chosen analysis technique.
The study was carried out in collaboration with the Urban Water Engineering research group at LTU within the framework of the research project "µrban plastics", funded by the Swedish Environmental Protection Agency. Heléne Österlund has been the supervisor for the master's thesis and Annelie Hedström the examiner.
For more details about Jonathan Svedin's thesis work see his report. Below is also a link to the above mentioned research project.