However, professor Sonia Kreidenweis and her team suspected that the air over the Southern Ocean would be least affected by humans and dust from the world’s continents.
Researchers found that the boundary layer air, which feeds the lower clouds over the Southern Ocean, was free from aerosol particles produced by human activity — including burning fossil fuels, planting certain crops, fertilizer production, and wastewater disposal — or transported from other countries around the world.
Researchers decided to study what was in the air, and where it came from, using bacteria in the air as a diagnostic tool to infer the properties of the lower atmosphere.
Research scientist and co-author of the study Thomas Hill explained that “the aerosols controlling the properties of SO (Southern Ocean) clouds are strongly linked to ocean biological processes, and that Antarctica appears to be isolated from southward dispersal of microorganisms and nutrient deposition from southern continents,” he said in a statement.
“Overall, it suggests that the SO is one of very few places on Earth that has been minimally affected by anthropogenic activities,” he added.
Scientists sampled the air in the marine boundary level — the part of the atmosphere that has direct contact with the ocean — while aboard a research boat traveling south to the Antarctic ice edge from Tasmania, Australia. Scientists then examined the composition of airborne microbes, which are found in the atmosphere and often dispersed thousands of kilometers by the wind.
Using DNA sequencing, source tracking and wind back trajectories scientist and first author Jun Uetake found that the microbes’ origins were from the ocean.
From the bacterial composition of the microbes, researchers concluded that aerosols from distant land masses and human activities, such as pollution or soil emissions caused by land use change, were not traveling south and into the air.
Scientists say that the results show a stark difference to all other studies from oceans both in the northern hemisphere and subtropics, which found that most microbes came from upwind continents.
Air pollution is already a global public health crisis, and kills seven million people each year, according to the World Health Organization (WHO).
More than 80% of people living in urban areas that monitor air pollution are exposed to air quality levels that exceed WHO guideline limits, the health organization said, and low- and middle-income countries suffer from the highest exposures.