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01/19/2023 13:17

Extensive field measurements of nitrous acid in the marine atmosphere

Tilo Arnhold Presse- und Öffentlichkeitsarbeit
Leibniz-Institut für Troposphärenforschung e. V.

York/Leeds/Leipzig. Field measurements around Cabo Verde in the tropical Atlantic have confirmed that nitrous acid (HONO) is widespread in the lower layers of the atmosphere above the oceans. Evidence for the release of this substance from photolysis of nitrate aerosols is now presented by an international research team led by the University of York (UK) in Science Advances, the open access journal of SCIENCE. Nitrous acid (HONO) plays a central role in tropospheric chemistry as an important source of the hydroxyl radical (OH) - in both polluted and clean environments.

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.
Historically, aerosol nitrate had been considered a permanent sink for NOx. This new process could increase the ability of the atmosphere to self-cleanse on a 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) - a collaborative venture between the University of York and the National Centre for Atmospheric Science (NCAS) - led extensive aircraft and ground-based observations in and around Cape Verde in the Atlantic Ocean in August 2019 and February 2020. The ARNA (Atmospheric Reactive Nitrogen over the remote Atlantic) field campaigns used the British atmospheric research aircraft FAAM BAe-146-301. Twelve flights were conducted with in situ measurements including Nitric Oxide (NO), Nitrogen dioxide (NO2), Nitrous acid (HONO), Ozone (O3), and aerosol surface area. Particulate nitrate (pNO-3) was determined from aerosol filters. Photolysis rates and OH radical concentrations were modelled using the global three-dimensional atmospheric chemistry model GEOS-Chem. At the Cape Verde Atmospheric Observatory (CVAO), Nitrogen oxide (NOx), Particulate nitrate (pNO-3), Ozone (O3) and photolysis rates are measured routinely. These were supplemented by HONO measurements during the ARNA campaigns.
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.”
It is also noted that nitrate aerosols are becoming increasingly important in the atmosphere as precursor ammonia emissions increase and ammonium sulphate aerosols decrease. "Thus, the formation of nitrogen oxides from nitrate aerosols could have important, increasing and previously unexplored effects on the trends and distributions of atmospheric oxidants," adds Dr Khanneh Wadinga Fomba of TROPOS, who has been researching aerosols on Cabo Verde for many years.
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.

Publication:

Simone T. Andersen, Lucy J. Carpenter, Chris Reed, James D. Lee, Rosie Chance, Tomás Sherwen, Adam R. Vaughan, Jordan Stewart, Pete M. Edwards, William J. Bloss, Roberto Sommariva, Leigh R. Crilley, Graeme J. Nott, Luis Neves, Katie Read, Dwayne E. Heard, Paul W. Seakins, Lisa K. Whalley, Graham A. Boustead, Lauren T. Fleming, Daniel Stone, Khanneh Wadinga Fomba (2023). Extensive field evidence for the release of HONO from the photolysis of nitrate aerosols. Sci. Adv. 9, eadd6266 (2023). https://doi.org/10.1126/sciadv.add6266
The research was funded by the National Environmental Research Council (NERC, grant NE/S000518/1), the National Centre for Atmospheric Research (NCAS), the SPHERES Natural Environment Research Council (NERC) Doctoral Training Partnership (DTP, grant NE/L002574/1), the European Research Council (ERC) under the European Union’s Horizon 2020 programme (project O3-SML; grant agreement no. 833290).

Further links:

Long-term observation of aerosol at CVAO (Cape Verde Atmospheric Observatory)
https://www.tropos.de/en/research/atmospheric-aerosols/long-term-trends-and-proc...

Cape Verde Atmospheric Observatory (CVAO)
https://amof.ac.uk/observatory/cape-verde-atmospheric-observatory-cvao/

ARNA (Atmospheric Reactive Nitrogen over the remote Atlantic)
https://gtr.ukri.org/projects?ref=NE%2FS000518%2F1

Facility for Airborne Atmospheric Measurements (FAAM)
https://www.faam.ac.uk/

The Leibniz Institute for Tropospheric Research (TROPOS) is a member of the Leibniz Association, which connects 97 independent research institutions that range in focus from the natural, engineering and environmental sciences via economics, spatial and social sciences to the humanities. Leibniz Institutes address issues of social, economic and ecological relevance. They conduct knowledge-driven and applied basic research, maintain scientific infrastructure and provide research-based services.
The Leibniz Association identifies focus areas for knowledge transfer to policy-makers, academia, business and the public. Leibniz institutions collaborate intensively with universities – in the form of “Leibniz ScienceCampi” (thematic partnerships between university and non-university research institutes), for example – as well as with industry and other partners at home and abroad.
They are subject to an independent evaluation procedure that is unparalleled in its transparency. Due to the importance of the institutions for the country as a whole, they are funded jointly by the Federation and the Länder, employing some 20,500 individuals, including 11,500 researchers.
The entire budget of all the institutes is approximately 2 billion euros. They are financed jointly by the Federal Government and the Länder. The basic funding of the Leibniz Institute for Tropospheric Research (TROPOS) is therefore financed by the Federal Ministry of Education and Research (BMBF) and the Saxon State Ministry of Science and the Arts (SMWK). The Institute is co-financed with tax revenues on the basis of the budget approved by the Saxon State Parliament.
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Contact for scientific information:

Dr. Khanneh Wadinga Fomba
Department Chemistry of the Atmosphere, Leibniz Institute for Tropospheric Research (TROPOS), Leipzig
Phone: +49 341 2717-7033
https://www.tropos.de/en/institute/about-us/employees/khanneh-wadinga-fomba

and
Professor Lucy Carpenter
UK principal investigator of the Cape Verde Observatory (CVAO)
Department of Chemistry, University of York, Heslington (UK)
Phone: +44 1904 324588
https://www.york.ac.uk/chemistry/staff/academic/a-c/lcarpenter/

or
Tilo Arnhold, Public relations, TROPOS
Phone: +49 341 2717-7189
http://www.tropos.de/aktuelles/pressemitteilungen/

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Original publication:

see main text

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More information:

https://www.york.ac.uk/news-and-events/news/2023/research/self-cleaning-of-marin... - New study shows ‘self-cleaning’ of marine atmosphere (Press release of the University of York, 18 January 2023)

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Measurements at the Cape Verde Atmospheric Observatory (CVAO).
Wadinga Fomba, TROPOS
Wadinga Fomba, TROPOS

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Criteria of this press release:
Journalists
Chemistry, Environment / ecology, Geosciences, Oceanology / climate
transregional, national
Research results, Scientific Publications
English

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