Author: Xiangtao  Jiang,   (University of Texas at Austin MSI)

Designation: 

Description:
The accumulation of plastic debris in the marine environment is an emerging concern worldwide, as plastics and the associated chemicals threaten marine organisms and ecosystems. It is, therefore, critical to understand environmental processes that can degrade plastics, such as photooxidation. Here we studied the photodegradation of plastic films and particles in seawater under 4 months UV exposure in a laboratory setup, which is equal to approximately 100 years of natural sunlight exposure in the ocean. The Fourier Transform Infrared spectroscopy results showed that absorption peaks at 1500-1800 and 3400-3600 cm^-1 occurred on the surface of high-density polyethylene (HDPE), low-density polyethylene (LDPE) and polystyrene (PS) plastics after the UV exposure, indicating the generation of ester and ketone functional groups by photooxidation. Loss of amorphous domains relative to crystalline was characterized by Raman spectroscopy and was non-linearly related to time acting as a timestamp. A plastic additive, Irgafos 168, present in several HDPE and LDPE samples based on pyrolysis gas chromatography-mass spectrometry results, disappeared after the UV exposure, which suggested that additives can be either leached out to surrounding seawater or photodegraded. We also found a clear decrease in molecular weight for PS and polyvinyl chloride (PVC) samples after the UV exposure, likely caused by chain scission reactions on the polymers induced by photooxidation.  While further experiments and analysis are still on going, our eventual goals are to interrogate photooxidation processes of different types of plastic polymers, identify and quantify the breakdown products and substance classes that leach into the seawater, and improve our understanding of the decay and fate of plastics in marine environments.

Category: Scientific Program Abstract > Special Sessions > SS10 Fate and Effects of Microplastics Across Aquatic Environments