FSU researchers discover that the sun, rain, turns asphalt binders into potentially toxic compounds

Tallahassee, Florida-Dramatic oil spills, including the Deepwater Horizon accident in the Gulf of Mexico 10 years ago, wonder what scientists, policy makers, and the public are doing with all that oil in the environment On the other hand, it can dominate headlines for months. However, the destinies of petroleum products that have intentionally spread over the globe for decades have far less attention to asphalt binders.

Studies by chemists at the National High Field Institute at Florida State University are now showing that asphalt binders leach thousands of potentially toxic compounds into the environment when exposed to the sun and water. I will. Research published in journal Environmental science and technology..

Asphalt binder, also known as asphalt cement, is an adhesive that holds stones, sand, and gravel on paved roads together. The heavy, black, sticky goo comes from the crude oil at the bottom of the barrel at the end of the distillation process.

Funded by the National Science Foundation and the State of Florida, MagLab is a world leader in petrochemistry researching the highly complex hydrocarbons that make up crude oil and its by-products. Using a high resolution ion cyclotron resonance (ICR) mass spectrometer, chemists have developed expertise to identify tens of thousands of different types of molecules that a drop can contain, the composition of which can vary over time, bacteria or We investigated how it changes with environmental conditions.

Ryan Rodgers, head of petroleum applications and head of Future Fuels Institute at MagLab, has long wanted to study asphalt binders using ICR equipment. This was a logical next step in his group’s longstanding efforts to better understand the structure and behavior of petroleum molecules, and their potential toxic effects. Previous studies have shown that soils and runoffs near paved roads have high concentrations of polycyclic aromatic hydrocarbons (PAHs), which are known to be carcinogenic. Rogers suspected there were points connecting these PAHs and asphalt binders, and he wanted to find them.

“The long-term stability of petroleum-derived materials in the environment has always been my curiosity,” said Rogers, who grew up in the Gulf of Florida. “Knowing the complexity of their composition and construction, it seemed very unlikely that they would be environmentally friendly.

He finally got a jug of asphalt binder from a local pavement company and handed the project to Dr. Sydney Niles. My name is Martha Chacón-Patiño, a Florida chemistry candidate and MagLab chemist. They designed an experiment in which they made a film of a binder on a glass slide, submerged it in water, illuminated it with a solar simulator for a week, and sampled the water at different times to see what it contained. did. They suspected that the energy of the sun would interact with active oxygen-containing compounds in the water with hydrocarbons in the binder, causing a process called photooxidation, creating a new class of molecules that would leach into water. ..

“We got this road sample and illuminated it in fake sunlight in the presence of water,” explained lead author Niles. “Subsequent examination of the water found that all of these petroleum-derived compounds were toxic and probably toxic. We also found that over time more compounds were leached.”

The hydrocarbons they found in the water contained more oxygen atoms. Scientists were convinced that the sun was actually the mechanism behind the process. This is because the control sample, which was stored in the dark, leached far fewer compounds and fewer oxygen atoms. In fact, the team discovered that the water-soluble organic compounds found in the water in the samples irradiated a week later were more than 25 times greater than the samples left in the dark. We also used a lab ICR magnet to detect over 15,000 different carbon-containing molecules in water from irradiated samples.

Given the general toxicity of PAHs, these results are the cause of concern, Niles and Rogers said. However, the team needs to do more experiments to investigate its toxicity.

“We have clearly shown that asphalt binders can produce water-soluble pollutants, but their impact and fate will be the subject of future research,” Rogers said.

They also plan further studies to pinpoint how compounds change and whether different categories of petroleum molecules behave differently.

Niles is worried about hydrocarbons both inside and outside the lab. If you forget to bring a bag of reusable produce to the grocery store, you’ll have to pick up your vegetables on the way to the cash register rather than use the plastic bag provided by the store. These discoveries are not good news for the planet, but she said, they could lead to positive change.

“Hopefully, that’s the motivation for the solution,” she said. “I hope engineers can use this information to find a better alternative, whether it’s a sealant that they put on top of asphalt to protect it, or something else that they use to pave the road. ”