TY - JOUR
T1 - Characterizing microplastic size and morphology of photodegraded polymers placed in simulated moving water conditions
AU - Hebner, Tayler S.
AU - Maurer-Jones, Melissa A.
N1 - Publisher Copyright:
© 2020 The Royal Society of Chemistry.
PY - 2020/2
Y1 - 2020/2
N2 - Aquatic plastic debris experiences environmental stressors that lead to breakdown into smaller micro-sized plastic particles. This work quantified microplastic formation with the environmental stressors of UV irradiation followed by mechanical strain induced by movement of water with an emphasis on connecting our results to changes in the materials chemical/physical properties. Polypropylene, polyethylene, and polyethylene terephthalate thin films and polypropylene injection-molded sheets were irradiated with 254 nm UV light, placed into aquatic microcosms, collected through sieving, and counted under a microscope. Results showed increasingly more particles in smaller size classes, the smallest being 74-177 μm. Mechanical strain from the turbulent water caused 2.3-3× more microplastics to be formed for the thinnest (∼25 μm) film and 1.4-2× more for thicker films and sheets. The most common morphology of microplastics was fibers, particularly in thicker polypropylene samples, which was attributed to absorbance of the photons and the changes observed in the crystallinity and glass transition as measured with differential scanning calorimetry (DSC). When irradiated for 24, 48, or 72 h, longer irradiation resulted in more microplastics formed by polypropylene films, which correlated with changes in the glass transition temperature as measured by DSC and the extent of oxidation as measured with FTIR. Irradiation at 300 nm produced fewer microplastics due to slower kinetics of phototransformations. Overall, this work evaluates the impact of combined photodegradation and water motion toward microplastic particles formed. It provides quantitative evidence that mechanical strain of water movement exacerbates photo-induced formation of microplastics and shows that the existence of fibers in natural systems can be the result of photodegradation.
AB - Aquatic plastic debris experiences environmental stressors that lead to breakdown into smaller micro-sized plastic particles. This work quantified microplastic formation with the environmental stressors of UV irradiation followed by mechanical strain induced by movement of water with an emphasis on connecting our results to changes in the materials chemical/physical properties. Polypropylene, polyethylene, and polyethylene terephthalate thin films and polypropylene injection-molded sheets were irradiated with 254 nm UV light, placed into aquatic microcosms, collected through sieving, and counted under a microscope. Results showed increasingly more particles in smaller size classes, the smallest being 74-177 μm. Mechanical strain from the turbulent water caused 2.3-3× more microplastics to be formed for the thinnest (∼25 μm) film and 1.4-2× more for thicker films and sheets. The most common morphology of microplastics was fibers, particularly in thicker polypropylene samples, which was attributed to absorbance of the photons and the changes observed in the crystallinity and glass transition as measured with differential scanning calorimetry (DSC). When irradiated for 24, 48, or 72 h, longer irradiation resulted in more microplastics formed by polypropylene films, which correlated with changes in the glass transition temperature as measured by DSC and the extent of oxidation as measured with FTIR. Irradiation at 300 nm produced fewer microplastics due to slower kinetics of phototransformations. Overall, this work evaluates the impact of combined photodegradation and water motion toward microplastic particles formed. It provides quantitative evidence that mechanical strain of water movement exacerbates photo-induced formation of microplastics and shows that the existence of fibers in natural systems can be the result of photodegradation.
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U2 - 10.1039/c9em00475k
DO - 10.1039/c9em00475k
M3 - Article
C2 - 31993606
AN - SCOPUS:85080906829
SN - 2050-7887
VL - 22
SP - 398
EP - 407
JO - Environmental Science: Processes and Impacts
JF - Environmental Science: Processes and Impacts
IS - 2
ER -