Sea Atmosphere Capable of Self-Cleaning

Marine Atmosphere Can Clean Itself Scientists have shed new light on the atmosphere's "self-cleaning" capacity. This self-cleaning process is necessary to remove gaseous pollutants and eliminate greenhouse gases such as methane from the atmosphere. Researchers were already aware that the atmosphere possessed this "self-cleaning" ability, but in a new study conducted at York University, experts have now demonstrated a new process that enhances the self-cleaning capacity of the marine atmosphere. Scientists used a combination of aircraft and ground-based observations to confirm the widespread presence of nitrous acid (HONO) formed through so-called "renoxification" in the remote Atlantic troposphere, while observing that photolysis of aerosol nitrate returned nitrogen oxides (NOx) and HONO to the marine atmosphere. Historically, aerosol nitrate was considered a permanent sink for NOx. This new process could mean that the atmosphere's self-cleaning capacity can be enhanced on a global scale. Scientists note that the findings, published in Science Advances, could be highly significant for atmospheric chemistry and may largely eliminate widespread uncertainty regarding the importance of renoxification. Scientists from Wolfson Atmospheric Chemistry Laboratories (WACL), with support from the Natural Environment Research Council (NERC), conducted extensive aircraft and ground-based observations around Cape Verde between August 2019 and February 2020. Lead author of the paper, Professor Lucy Carpenter, explained: "Importantly, the observations showed that the efficiency of renoxification increased with relative humidity and decreased with nitrate concentration. This observation reconciled very large inconsistencies in renoxification rates found in multiple laboratory and field studies. It was also consistent with renoxification occurring on the surface of aerosols, a new and exciting finding with implications for how this fundamental process is controlled and parameterized in models." The recycling of nitrogen oxides back onto nitrate aerosol may have significant, growing and yet undiscovered implications for the trends and distribution of atmospheric oxidants such as tropospheric ozone, an important greenhouse gas.

Source

More information: Simone Andersen et al, Extensive field evidence for the release of HONO from the photolysis of nitrate aerosols, Science Advances (2023). DOI: 10.1126/sciadv.add6266. www.science.org/doi/10.1126/sciadv.add6266 / Journal information: Science Advances / Provided by University of York / https://phys.org/news/2023-01-self-cleaning-marine-atmosphere.html