EGU General Assembly 2022
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the Creative Commons Attribution 4.0 License.

Insights into NOx and HONO in the subtropical marine boundary layer during MarParCloud campaign at Cape Verde

Andreas Tilgner1, Ying Jiang2, Erik H. Hoffmann1, and Hartmut Herrmann1
Andreas Tilgner et al.
  • 1Leibniz-Institut für Troposphärenforschung (TROPOS), Atmospheric chemistry department (ACD), Leipzig, Germany
  • 2Environment Research Institute, Shandong University, Qingdao, Shandong, 266237, China

Chemical processing of reactive nitrogen species, especially NOx(=NO+NO2) and nitrous acid (HONO), determines/alters critically the photochemical ozone production in the troposphere, affecting the climate change, biological cycle and human healthy. However, the characteristics and sources of nitrous acid (HONO) and NOin the remote marine atmosphere are still poorly understood. Herein, based on the data sets of HONO-related species as well as other parameters measured during MarParCloud campaign at Cape Verde in October 2017, the multiphase chemistry model SPACCIM equipped with the state-of-the-art multiphase chemistry mechanism CAPRAM was adopted with input of current literature parametrizations for various HONO sources in the tropospheric boundary layer (gas reaction of NO and OH, ocean-surface-mediated conversion of NOto HONO, NOreacted with organics on mineral dust, NHoxidation process, and dust-surface-photocatalytic conversions of reactive nitrogen species to HONO) to reveal the relative importance of each source for HONO in the remote boundary layer at Cape Verde. Each simulation was performed for 72 hours in different clusters obtained from the backward trajectories model analysis with HYSPLIT. The simulations well reproduced the observed HONO level and its diurnal pattern, and significantly improved the model performance for NOand Oin every cluster after 72 hours of operation, when considering the mechanisms of dust-surface-photocatalytic conversions of reactive nitrogen species. Furthermore, photolysis of the absorbed HNOon the dust is modelled to be the prevailing contributor for the daytime HONO at Cape Verde, which accounted for about 56%, following by the photo-enhanced of NOabsorbed on the dust (41%). In contrast, the ocean-surface-mediated conversion of NOto HONO and other pathways were found unimportant for HONO formation at Cape Verde. For OH sources, HONO photolysis only accounted for a small proportion source (~3%) of the ambient OH level in remote marine boundary layer due to the low HONO concentration at Cape Verde. In summary, this study highlights the key role of dust aerosols in the formation of HONO and NOat Cape Verde.

How to cite: Tilgner, A., Jiang, Y., Hoffmann, E. H., and Herrmann, H.: Insights into NOx and HONO in the subtropical marine boundary layer during MarParCloud campaign at Cape Verde, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4609,, 2022.

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