Academic journal

Plastic shopping bags free thousands of di


Although plastics are durable and strong, a little sunlight can split them into microscopic pieces and stimulate reactions, producing new molecules that can end up in the environment. But how the polymers and additives in these materials influence this process is a mystery. Now researchers reporting in ACS ‘ Environmental sciences and technologies show that additives in commercial shopping bags increase the ability of sunlight to convert these solid materials into thousands of dissolved compounds within days.

Once plastic pollution enters the environment, its fate is still largely unknown, especially in aquatic ecosystems. Some plastic items, such as polythene shopping bags, float in water, exposing them to direct sunlight. Previous researchers have shown that the pure polymers commonly used to make these items produce water-soluble molecules and gases when placed in ultraviolet light, a component of sunlight. However, plastics in consumer goods are not pure; a variety of organic carbon based additives and mineral additives are mixed to give them color or make them more stable. So Collin Ward and his colleagues wanted to see exactly how the composition of single-use shopping bags influenced the dissolved compounds generated by sunlight over short periods of time.

With X-ray diffraction, the researchers examined four polyethylene plastic bags from big box retailers and a pure polyethylene polymer film for mineral additives. No additives were identified in the pure polymer, but calcium carbonate and titanium dioxide were found in three of the bags, and only calcium carbonate was found in the fourth bag. Next, the researchers put pieces of the plastic and polymer bags into separate containers with water, then in the dark or in simulated daylight for a week. Some water soluble compounds were released from the various pieces in the dark. But in sunlight, more compounds were released, ranging from 5,000 to 15,000 dissolved compounds, which equates to a 1.1 to 50-fold increase in the number of compounds released in the dark. Of the roughly 9,000 molecules generated by the pure polymer when exposed to sunlight, only about a quarter overlapped those of the bags. Based on these results, the researchers claim that the reactions of sunlight with solid plastics can turn them into a plethora of water-soluble compounds whose levels and identities vary depending on the additives used.

The authors acknowledge funding from the Seaver Institute, the Gerstner Family Foundation, the Woods Hole Oceanographic Institution, and the National Science Foundation Graduate Research Fellowship Program, Division of Chemistry and Division of Materials Research.

The American Chemical Society (ACS) is a nonprofit organization accredited by the United States Congress. ACS’s mission is to advance the broader chemistry business and its practitioners for the benefit of the Earth and all of its inhabitants. The Company is a world leader in promoting excellence in science education and access to information and research related to chemistry through its multiple research solutions, peer-reviewed journals, its scientific lectures, electronic books and weekly periodicals. Chemistry and Engineering News. ACS journals are among the most cited, trusted, and widely read in the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate advancements by organizing, connecting and analyzing global scientific knowledge. The main offices of ACS are located in Washington, DC, and Columbus, Ohio.

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