A study by the Woods Hole Institute of Oceanography in the United States shows that polystyrene may degrade in decades to hundreds of years after exposure to sunlight, rather than being able to last for thousands of years in the environment as previously thought by scientists.
Polystyrene is a kind of colorless and transparent thermoplastic, which is widely used in many consumer and industrial products. It is one of the most widely used plastics in the world. The chemical structure of polystyrene is so complex that ordinary microorganisms can't degrade it. So scientists estimate that polystyrene can last for thousands of years or even longer in the environment. As early as the 1970s, scientists have detected polystyrene in the ocean. Because of its wide use and difficult degradation, this polymer has now become an important source of pollution in the global ecological environment.
To test whether polystyrene can survive for thousands of years or even forever, researchers at the Woods Hole Oceanography Institute conducted a special experiment. They put five commercially available polystyrene samples in water and exposed them to simulated sunlight three times stronger than the equatorial sunlight. The results showed that simulated sunlight partially oxidized all five samples into dissolved organic carbon. The researchers calculated that in the natural environment of 0 ° - 50 ° north latitude, that is, the vast area extending from the equator to the southern border of Canada, it only takes decades to complete this partial oxidation process, while it takes hundreds of years to completely oxidize polystyrene to carbon dioxide. That is to say, sunlight can partially or completely degrade polystyrene in decades to hundreds of years, much faster than previously thought.
In addition, the researchers also found that additives can change the relative sensitivity of polystyrene photochemical oxidation and affect the degradation rate; compared with sunlight exposure, temperature has limited influence on the photochemical oxidation of polystyrene, which is not the main driving factor of its oxidation rate.
Researchers point out that many international institutions believe that polystyrene can last for thousands of years in the environment, and make relevant policies based on it. Their research results challenge this policy basis, which will help to improve the life estimation method of plastic environment, improve the understanding of the amount of plastic in land and sea, improve the accuracy of risk assessment related to plastic pollution, and then help relevant agencies to formulate more scientific response strategies.
Relevant papers were published in the environmental science and technology express on the 10th.
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