Microplastic particle versus fiber generation during photo-transformation in simulated seawater

Microplastic particles and fibers are increasingly being detected in our surface and ground waters as well as within a wide range of aquatic species. Their presence in the environment is largely due to in situ generation from physical and chemical weathering of larger plastics, and thus has left environmental community concerned in the post-banned era of microbead use in personal care products through the passage of Microbead-Free Waters Act in the United States. To improve understanding of secondary microplastic formation, accelerated weathering has been conducted on four materials (high-density polyethylene, high impact polystyrene, nylon 6, and polypropylene) under ultraviolet radiation (equivalent to 44 days in full sun) in simulated seawater. Physical and chemical characterization of the plastics were completed following ultraviolet exposure. This simulated weathering generated microfibers from high-density polyethylene and nylon 6, while high impact polystyrene and polypropylene did not physically degrade. The techniques used were applied to sediment samples containing plastic pellets collected from Cox Creek in Port Comfort, TX (near a large plastics manufacturer), which were purified for analysis and were found to contain microplastics composed of polypropylene and polyethylene. These findings can be used to determine degradation pathways and plastic source tracking, which can facilitate risk assessment and environmental management. Photo-weathering generate microfibers from high-density polyethylene and nylon 6, while high impact polystyrene and polypropylene do not physically degrade. [Display omitted] •Microplastic fiber/particle generation from UV was dependent on plastic type.•High-density polyethylene and nylon 6 produced microplastic fibers.•High impact polystyrene and polypropylene did not physically degrade.•Molecular structure determines degree of oxidation resulting from UV radiation.•The methodology was utilized to identify microplastics in environmental samples.