Science and Technology Daily Washington, October 12 (reporter Liu Haiying) Woods Hole Oceanographic Institution of the United States, a study shows that polystyrene exposed to sunlight, may degrade within decades to hundreds of years, rather than as previously thought scientists can persist in the environment for thousands of years.

Polystyrene is a colorless and transparent thermoplastic that is widely used in many consumer and industrial products and is one of the most widely used plastics in the world. The chemical structure of polystyrene is complex and cannot be degraded by ordinary microorganisms, so scientists estimate that it can persist in the environment for thousands of years or more. As early as the 1970s, scientists detected polystyrene in the ocean, because it is widely used, difficult to degrade, the polymer has become a significant source of pollution in the global environment.

To see if polystyrene really can last for thousands of years or even forever, researchers at the Woods Hole Oceanographic Institution conducted a special experiment. They placed five commercially available samples of polystyrene in water and then exposed them to simulated sunlight three times stronger than equatorial sunlight. They found that the simulated sunlight partially oxidized all five samples to dissolved organic carbon. The researchers did their calculations and concluded that at latitude 0. -50° In the natural environment, that is, in the vast area stretching from the equator to the southern border of Canada, this part of the oxidation process takes only a few decades; To fully oxidize polystyrene to carbon dioxide, it would take hundreds of years. This means that sunlight can partially or completely degrade polystyrene over decades to centuries, much faster than previously thought.

In addition, the researchers also found that the additives can change the relative sensitivity of photochemical oxidation of polystyrene, affecting the rate of degradation; Compared with sunlight exposure, temperature has a limited effect on the photochemical oxidation of polystyrene and is not the main driving factor for its oxidation rate.

The researchers point out that many international bodies have agreed that polystyrene can persist in the environment for thousands of years, and have based their policies on this. Their findings challenge this policy basis and will help refine methods for estimating the environmental lifespan of plastics, improve understanding of the amount of plastic on land and in the ocean, improve the accuracy of risk assessments associated with plastic pollution, and help agencies develop more scientific response strategies.

The related paper was published in Environmental Science and Technology Letters on the 10th.

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