A new study conducted by the Colorado State University has defined the area that has the cleanest air in the world: the remote Southern Ocean that encircles Antarctica.
The swift climate change driven by human activities has left no area without pollution. But, Professor Sonia Kreidenweis and her team from the Department of Atmospheric Science suspected the air directly over the remote Southern Ocean won't be affected by pollution or contain aerosols produced by human activities or exported from remote lands.
During the study, the researchers examined the region by using the bacteria in the air over the Southern Ocean as a diagnostic tool.
The study was published in the Proceedings of the National Academy of Sciences journal.
The researchers also examined the composition of airborne microbes captured from the ship they were on, and found that Antarctica appears to be isolated from microorganisms linked to aerosols, which makes it one of very few places on Earth that has been minimally affected by anthropogenic activities.
Using DNA sequencing, source tracking and wind back trajectories, the team determined the microbes' origins were marine, sourced from the oceans, suggesting aerosols from distant land masses and human activities, such as pollution or soil emissions driven by land use change, were not traveling south into Antarctic air.
These results counter all other studies from oceans in the subtropics and northern hemisphere, which found that most microbes came from upwind continents. But the diagnostic tool used in the study was decisive in validating the hypothesis of Kreidenweis and her team.
In a report published on the Colorado State University's website, research Thomas Hill, coauthor on the study, said: "The air over the Southern Ocean was so clean that there was very little DNA to work with."
"We treated the samples as precious items, taking exceptional care and using the cleanest technique to prevent contamination from bacterial DNA in the lab and reagents, so we can reach more accurate results," Hill added.
