Is there still an unpolluted sanctum on Earth where several billions of people reside? The answer is yes. Scientists have recently discovered an atmospheric area that is over the Southern Ocean between South Australia and Antarctica, where the cleanest air on Earth was found, and has not yet been affected by human activities.

The atmosphere is circulated around the world, though scientists wish to know if there remains to be a utopia that has yet to be touched by the humans, which prompted the research team at the Colorado State University to first suspect that the air above the Southern Ocean may be least impacted by humans and continental dust.

First, the diversified composition of the atmosphere contains aerosol particles that suspend within the gaseous medium, which can be categorized as natural source and artificial source according to its cause of generation. These aerosol particles are able to reflect the energy of the sun back to the space, and are crucial to the climate and weather model, though their uneven distribution makes it important to grasp on their paths and locations.

The research team at the Colorado State University led by scientist Sonia Kreidenweis collaborated with the Bureau of Meteorology to analyze the substances above the Southern Ocean and their sources, and discovered that the air composition at the low cloud boundary of the Southern Ocean is extremely primitive, containing no aerosol particles and microorganisms produced by human activities or transported from distant land.

Air samples were first collected from above the Southern Ocean, then a DNA sequencing was implemented to analyze the origin of the microorganisms within the samples, where the research personnel discovered that the aerosols within the clouds at the Southern Ocean are closely related with marine organisms rather than the microorganisms that are diffused southward. Furthermore, the closer an area is to Antarctica, the less diversity of bacteria is (the composition of microorganisms is also different according to the atmosphere in various latitudes), indicating that the Southern Ocean is one of the few areas on Earth that has sustained the least impact from human activities.

Although having come from a certain longitudinal extent, the research samples are able to explain that the air above the Southern Ocean is one of the very few areas that are highly resistant to human activities. The next step for the research team is to continue probing into the seasonality and annual changes of the aerosols in the specific area, and proceed to the Arctic to investigate how microorganism affect the property of clouds. The new thesis will be published on the <Proceedings of the National Academy of Sciences>.

 (Cover photo source: pixabay)