Preprints
https://doi.org/10.5194/acp-2021-42
https://doi.org/10.5194/acp-2021-42

  21 Jan 2021

21 Jan 2021

Review status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Reactive nitrogen around the Arabian Peninsula and in the Mediterranean Sea during the 2017 AQABA ship campaign

Nils Friedrich1, Philipp Eger1, Justin Shenolikar1, Nicolas Sobanski1, Jan Schuladen1, Dirk Dienhart1, Bettina Hottmann1, Ivan Tadic1, Horst Fischer1, Monica Martinez1, Roland Rohloff1, Sebastian Tauer1, Hartwig Harder1, Eva Y. Pfannerstill1, Nijing Wang1, Jonathan Williams1, James Brooks2, Frank Drewnick3, Hang Su4, Guo Li5, Yafang Cheng5, Jos Lelieveld1, and John N. Crowley1 Nils Friedrich et al.
  • 1Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, 55118, Germany
  • 2Centre for Atmospheric Science, University of Manchester, Manchester, M13 9PL, UK
  • 3Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, 55118, Germany
  • 4Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, 55118, Germany
  • 5Minerva Research Group, Max Planck Institute for Chemistry, Mainz, 55118, Germany

Abstract. We present ship-borne measurements of NOx (≡ NO + NO2) and NOy (≡ NOx + gas- and particle-phase organic and inorganic oxides of nitrogen) in summer 2017 as part of the expedition Air Quality and climate change in the Arabian Basin (AQABA). The NOx and NOz (≡ NOy–NOx) measurements, made with a thermal dissociation cavity-ringdown-spectrometer (TD-CRDS), were used to examine the chemical mechanisms involved in the processing of primary NOx emissions and their influence on the NOy budget in chemically distinct marine environments, including the Mediterranean Sea, the Red Sea, and the Arabian Gulf which were influenced to varying extents by emissions from shipping and oil and gas production. In all regions, we find that NOx is strongly connected to ship emissions, both via direct emission of NO and via the formation of HONO and its subsequent photolytic conversion to NO. Mean NO2 lifetimes were 3.9 hours in the Mediterranean Sea, 4.0 hours in the Arabian Gulf and 5.0 hours in the Red Sea area. The cumulative loss of NO2 during the night (reaction with O3) was more important than daytime losses (reaction with OH) over the Arabian Gulf (by a factor 2.8) and over the Red Sea (factor 2.9), whereas over the Mediterranean Sea, where OH levels were high, daytime losses dominated (factor 2.5). Regional ozone production efficiencies (OPE) ranged from 10.5 ± 0.9 to 19.1 ± 1.1. This metric quantifies the relative strength of photochemical O3 production from NOx, compared to the competing sequestering into NOz species. The largest values were found over the Arabian Gulf, consistent with high levels of O3 found in that region (10–90 percentiles range: 23–108 ppbv). The fractional contribution of individual NOz species to NOy exhibited a large regional variability, with HNO3 generally the dominant component (on average 33 % of NOy) with significant contributions from organic nitrates (11 %) and particulate nitrates in the PM1 size range (8 %).

Nils Friedrich et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-42', Anonymous Referee #1, 16 Feb 2021
  • RC2: 'Comment on acp-2021-42', Anonymous Referee #2, 17 Feb 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-42', Anonymous Referee #1, 16 Feb 2021
  • RC2: 'Comment on acp-2021-42', Anonymous Referee #2, 17 Feb 2021

Nils Friedrich et al.

Nils Friedrich et al.

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Short summary
This paper uses NOx and NOz measurements from the 2017 AQABA ship campaign in the Mediterranean Sea and around the Arabian Peninsula to examine the influence e.g. of emissions from shipping and oil and gas production. Nighttime losses of NOx dominated in the Arabian Gulf and in the Red Sea, whereas daytime losses were more important in the Mediterranean Sea. Nitric acid and organic nitrates were the most prevalent components of NOz.
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