Shining some sunlight on plastics degradation
S. Himmelstein | October 11, 2019The long-term persistence of polystyrene adds to the environmental burden of discarded plastics. Commonly used in consumer products, packaging and in other applications, polystyrene is thought to endure for millenia, largely due to its resistance to microbial degradation. A route for considerably shortening the decomposition time of this plastic on the order of decades has been demonstrated by researchers from Woods Hole Oceanographic Institution.
Solar simulators were used to observe the relatively rapid decomposition of polystyrene to carbon dioxide as a photochemical oxidation product. Five different commercially available polystyrene samples were converted to CO2 by sunlight.
Under sunlight exposure, the average lifetimes of complete photochemical oxidation of polystyrene materials are on the order of centennial time scales. Average lifetimes of partial photochemical oxidation are on the order of decades.
The influence of additives, which can determine polystyrene color, flexibility and other physical features, was also analyzed. Additives were shown to modify the relative susceptibility to complete and partial photochemical oxidation of polystyrene and accelerated breakdown by shifting light absorbance and reactivity to longer wavelengths.
The research published in Environmental Science and Technology Letters indicates that sunlight exposure, rather than resistance to biodegradation, governs the environmental persistence of this plastic.
Sunlight destroys just about everything except rocks.
However, it still takes a long time to degrade one of those EPS flotation blocks after they wash up on a beach after a storm. But not millenia.