Around 99,200 tons of PAHs infiltrate the oceans every month.
Polycyclic aromatic hydrocarbons (PAHs) — organic compounds containing only hydrogen and carbon — are released into the atmosphere from burning coal, oil, gasoline, trash, wood, and other anthropogenic and natural sources, and they are transported from the land to the ocean via the atmosphere.
Now, a new study published in the journal Nature Geoscience, and led by the Spanish National Research Council (CSIC), has highlighted the importance of understanding the dynamics of these contaminants in order to grasp their effects on both ocean ecosystems and the global carbon cycle.
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Of all the carbon deposited into the oceans globally, aromatic hydrocarbons account for 15 percent. In fact, every month, around 99,200 tons of PAH contaminants enter the Atlantic, Pacific, and Indian oceans from the atmosphere, which is four times greater than the 2010 Deepwater Horizon oil spillage in the Gulf of Mexico — considered the worst oil spill in history.
"Polycyclic aromatic hydrocarbons, as well as other aromatic compounds are ubiquitous pollutants abundant in the environment. Furthermore, they are a component of organic carbon which to date has not been studied in depth in terms of atmosphere-ocean flows," explains Jordi Dachs, a researcher at CSIC Institute of Environmental and Water Studies in Barcelona, in a press release.
During the Malaspina Expedition, in a project consisting of close to 50 research groups, and managed by CSIC and the Spanish Economy and Finance Ministry, the study team collected samples of air (gases and aerosols), taken with high volume collectors (seen in the image below), as well as samples of both rain and water from the ocean surface.
High volume collectors aboard the vessel Hespérides. Photo credit: Joan Costa/CSIC
Once the organic compounds were isolated, they were measured and quantified, and depending on their concentrations, a calculation was made of both the flow and exchange between the atmosphere and ocean.
Currently, the specific consequences of PAHs are not certain, but the researchers point out that, in the long term, they could affect ocean life given their toxicity. What’s more, they can cause alterations in the formation of aerosols in the marine atmosphere, which affects cloud formation cycles.
"We had very little information about the magnitude of pollution from polycyclic aromatic hydrocarbons in the open ocean. It was necessary to carry out a study on a global scale to know the relevance of these flows on a worldwide scale," said Belén González-Gaya, a researcher at the Institute of Environmental Diagnostics and Water Studies, and the Institute of Organic Chemistry in Madrid, in the release.
The next step of the project is to trace a more detailed flow of these pollutants in the oceans, and determine their potential impacts on living creatures.
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