While most air quality research focuses on climate change, air pollution, and air quality, scientists from Colorado State University (CSU) have conducted an opposite study. As the first of its kind, the study shows how the team collected samples from the Southern Ocean (SO) and found what may be Earth's cleanest pocket of air.
Professor Sonia Kreidenweis and her team, based in the Department of Atmospheric Science, identified an atmospheric region at 40 degrees south latitude which is unaltered by human-related activities. They measured the bioaerosol composition of the ocean, find the air to be free from aerosol, or particles produced by human activities or transported from elsewhere.
Anthropogenic activity has vastly affected weather and climate, causing global warming and making it difficult for researchers to find any area on the plant, both land, and sea, that remains untouched by humans. Kreidenweis and her team originally suspected that the air directly over the remote Southern Ocean that encircles Antarctica would have some dust from other continents or be affected by activity.
Thomas Hill, one of the authors, said that they 'were able to use the bacteria in the air over the Southern Ocean as a diagnostic tool to infer key properties of the lower atmosphere.' They found that Southern Ocean clouds had aerosols 'linked to ocean biological processes and that Antarctica appears to be isolated from southward dispersal of microorganisms and nutrient deposition from southern continents.
Overall, it suggests that the SO is one of the very few places on Earth that has been minimally affected by anthropogenic activities. Aboard the Research Vessel Investigator traveling from Tasmania to the Antarctic, Researcher Jun Ueteke examined what composed the airborne microbes captured during the expedition. DNA sequencing revealed that microorganisms that usually disperse thousands of miles by the wind all over the atmosphere don't travel southward into Antarctic air, while other regions are evident of pollution and soil emissions from the change of land use.
Pristine Air
The pristine air over the Southern Ocean was so clean that there was minimal DNA to work with. Hill attributed the quality of their results to Uetake and Katherine Moore's, a graduate student, clean lab process. 'Jun and Kathryn, at every stage, 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," Hill said.
The results counter all studies regarding the other oceans which contain microbes from upwind continents. 'Plants and soil are strong sources of particles that trigger freezing of supercooled cloud droplets, known as ice-nucleating particles,' explained the study. Precipitation becomes enhanced from reduced cloud reflectivity, increasing how much sunlight reaches the Earth's surface and changing radiative balance.
Above the Southern Ocean, sea spray emissions are a dominant material for forming liquid cloud droplets. Ice-nucleating particle concentrations, known to be found in SO clouds to form ice crystals, 'are the lowest recorded anywhere on the planet.'
Pure, Clean Air
Evidence of marine bioaerosol also suggests that the SO creates distinct conditions as it is the largest wind-driven current on earth. The researchers concluded that bacterial composition was constrained by latitude and longitude, with ocean biological processes as a driving factor for the clean air.
With international efforts of battling climate change, it can only be hoped that the Southern Ocean's pure, clean air remains preserved, and even increase in the area if human activity can be reversed from the root of damage into the direction of a greener earth.
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