The Effect of Ultraviolet Light on the Photodegradation Rate of Three Different Types of Plastic on Beaches

Calla Reardon and Sally Bouley, Narragansett High School, Narragansett, RI, United States
Worldwide, 260 million tons of plastic is produced every year. Out of this amount, 10% of the plastic ends up in the ocean and will eventually wash up on beaches where it will take many years to photo degrade in the ultraviolet light from the sun. We live in a coastal community, so by going to beaches frequently, it is obvious to us how often plastic washes onto the shore, and how it affects animals and plants that live in these environments. We are studying the rate that the most common plastics such as PET (polyethylene terephthalate), HDPE (high-density polyethylene), PP (polypropylene), LDPE (low-density polyethylene), and styrofoam (polystyrene foam) photodegrade in UV light. These five plastics are the most common types of plastic that are found washed up on beaches. Photodegradation is a process in which ultraviolet radiation from the sun slowly breaks down plastics. Our research helps to show how long it takes different types of plastic to break down. We can use this information to raise awareness about how plastics should be used less commonly because of the many years that it takes to break down. We are testing this idea by putting pieces of water bottles made of PET, pieces of milk jugs, made of HDPE, plastic bottle caps made of PP, pieces of plastic bags made of LDPE, and pieces of styrofoam cups in a beach-like environment, and leaving them under the same strength UV light bulbs and calculating the mass of the plastic every few days and recording how the mass changes. This will show us the rate that each type of plastic was breaking down, and therefore help us determine which types of plastic biodegrade faster or slower than others. During this experiment, we expect to find that all five plastics will take a very long time to photodegrade. Using this information, it is clear that some plastics will decompose faster than others in ultraviolet light. We can also assume that these plastics will decompose faster than other plastics under most conditions. Through our research, we learned that all types of plastic takes many years to decompose and it is important to spread awareness about limiting the use of plastic. For example, in our community, plastic bags have been banned and all stores have switched to using either paper bags or reusable bags. This information shows the importance of avoiding use plastic and recycling any plastic that is used.