Scientists from the University of York have discovered that the ‘self-cleaning’ capacity of the atmosphere is better than previously understood, potentially resulting in significant implications for atmospheric chemistry.
Scientists were able to identify specific chemical reactions that involve reactive nitrogen species, using a combination of airborne and ground-based measurements, and found that the marine atmosphere has a better ability to self-clean than previously understood.
A well-known phenomenon, the atmosphere’s essential process of self-cleaning regulates and removes gaseous pollutants, mainly through production of a chemical species known as the hydroxyl radical (OH).
Scientists were able to confirm the widespread presence of nitrous oxide (HONO) in the remote Atlantic troposphere, with results suggesting that HONO was formed by ‘renoxification’, whereby sunlight breaks down aerosol nitrate and returns nitrogen oxides to the atmosphere.
The research team says the findings could be highly significant for atmospheric chemistry and will help to address previous uncertainties. Self-cleaning of the marine atmosphere, via renoxification, could have unexplored implications for concentrations of ozone and greenhouse gases.
Lucy Carpenter, professor of atmospheric chemistry at the University of York, said, “Importantly, the observations showed that the efficiency of renoxification increased with relative humidity and decreased with the concentration of nitrate. This observation reconciled the very large discrepancies in the rates of renoxification found across multiple laboratory and field studies. It was also consistent with renoxification occurring on the surface of aerosols, rather than within their bulk, a new and exciting finding with implications for how this fundamental process is controlled and parameterized in models.”
Observations were made in 2019 and early 2020 around Cape Verde in the tropical Atlantic Ocean, almost 600km off the coast of Northwest Africa. Due to its location, the archipelago acts as a natural laboratory with relatively low concentrations of human emissions. The team was able to capture the airborne and ground-based measurements by using the National Centre for Atmospheric Science’s FAAM Airborne Laboratory and Cape Verde Atmospheric Observatory, located on the small island of São Vicente.
To view the complete study published in the journal Sciences Advances, click here.