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New study shows ‘self-cleaning’ of marine atmosphere

Posted on 18 January 2023

Scientists have shed new light on the ‘self-cleaning’ capacity of the atmosphere.

The team led extensive aircraft and ground-based observations in and around Cape Verde

This process of self-cleaning is essential to remove gaseous pollutants and regulate greenhouse gases such as methane from the atmosphere.

Researchers were already aware that the atmosphere had this ‘self-cleaning’ ability, but in a new study from the University York, experts have now shown a new process that increases the ability of the marine atmosphere to self-cleanse.

Using a combination of aircraft and ground-based observations, scientists were able to confirm the widespread presence of nitrous oxide (HONO) in the remote Atlantic troposphere formed by so-called “renoxification”, whereby photolysis of aerosol nitrate returns nitrogen oxides (NOx) and HONO to the marine atmosphere.  

Global scale

Scientists say the findings, published in Sciences Advances, could be highly significant for atmospheric chemistry and largely reconcile widespread uncertainty on the importance of renoxification.

With funding from the Natural Environmental Research Council (NERC), scientists from the Wolfson Atmospheric Chemistry Laboratories (WACL) led extensive aircraft and ground-based observations in and around Cape Verde in August 2019 and February 2020. 

Recycling

Lead author, Professor Lucy Carpenter 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 parameterised in models.”

Recycling of nitrogen oxides on nitrate aerosol could have important, increasing, and as yet unexplored implications for the trends and distributions of atmospheric oxidants such as tropospheric ozone, an important greenhouse gas. 

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