Oil residues can travel over 5,000 miles on ocean debris, study finds

When oily plastic and glass, as well as rubber, washed onto Florida beaches in 2020, a community group shared the mystery online, attracting scientists’ attention. Working together, they linked the black residue-coated debris to a 2019 oil slick along Brazil’s coastline. Using ocean current models and chemical analysis, the team explains in ACS’ Environmental Science & Technology how some of the oily material managed to travel over 5,200 miles (8,500 kilometers) by clinging to debris.

“The research findings of our study would not have been possible without the dedication of the Friends of Palm Beach,” says Bryan James, lead author of the study and a researcher at Northeastern University. “Their long-term knowledge of the local marine debris enabled them to notice when unique and interesting items like oily plastic comes ashore. If they hadn’t been willing to investigate and share their observations, this discovery would still be lost at sea.”

Although some plastics can drift thousands of miles on ocean currents, crude oil or refined petroleum usually doesn’t. Instead, sunlight and microbes break down oil within a few hundred miles (300 kilometers) of where it entered the water. So, in 2020, the source of oily plastic bottles and glass containers along the shore in Palm Beach, Florida, was curious to the Friends of Palm Beach cleanup group. With no spills reported nearby, the group’s main clues about the oil’s source were the bottle labels in Portuguese, Spanish and English, and large chunks of rubber that had also washed up. The group became community scientists as some members teamed up with international researchers led by James and Christopher Reddy at Woods Hole Oceanographic Institution to find the origin of the oil and plastic pollution.

James, Reddy and their colleagues hypothesized that the oily plastic and rubber littering the beach in Florida could have the same origin as similar pollution found on Brazil’s coast in late 2019. And the source of the oil and rubber might be the SS Rio Grande, a sunken World War II supply ship in the Atlantic Ocean. To test their hypothesis, the researchers conducted computer simulations and oil spill forensic analyses.

• Origin: Ocean current models traced the plastic bottles backwards in time, predicting origins spanning from the Gulf of Mexico, Central America and Brazil.
• Travel time: Additional models estimated that the oily debris drifted for 240 days, which is a timeframe consistent with currents carrying material from the 2019 Brazil oil spill to the Florida coast.
• Chemical analyses: Several of the oily residues collected from the Florida debris showed evidence of refining, and the “chemical fingerprints” of the oily plastic matched those collected from the Brazil oil spill.

Reddy concludes that this work demonstrates an additive contaminant effect where plastic pollution can transport oil pollution far beyond its origin, and it expands on the current understanding of “petroplastic” — a recently recognized form of plastic pollution from humans.

The authors acknowledge collaboration from the Friends of Palm Beach and the Brazilian National Council for Scientific and Technological Development (Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq) Research Productivity Fellowship and PQ-1 grant, the Long Term Ecological Research Program-Semi-Arid Coast of Brazil (Programa de Pesquisa Ecológico de Longa Duração Costa Semiárida do Brasil, PELD-CSB), the Alexander Von Humboldt Foundation-CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) fellowships, the I-plastics Consortium within the Joint Programming Initiative Healthy and Productive Seas and Oceans Cearense Foundation for Scientific and Technological Development Support (Fundação Cearense de Apoio ao Desenvolvimento Cientifico e Tecnológico, FUNCAP), the Ceará Foundation for Scientific and Technological Development Support (FUNCAP) Chief Scientist Program, the Coordination for the Improvement of Higher Education Personnel within the Ministry of Higher Education in Brazil, the U.S. National Science Foundation, the State of Florida, the Woods Hole Oceanographic Institution’s Independent Research and Development Program, and the Natural Sciences and Engineering Research Council of Canada.

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