Riel Carlo O. Ingeniero

Atmospheric nitric oxide (NO) is a pollutant and climate‐relevant trace gas. Dissolved NO accumulates in the surface ocean and therefore the ocean is a natural source of atmospheric NO. It is generally assumed that NO in the surface ocean is produced photochemically from nitrite (NO ₂ ⁻ ). Here, we present the first dissolved NO measurements in the oligotrophic North Atlantic Ocean during an east‐to‐west transect (December 2021/January 2022). NO concentrations and mean saturations ranged from 9.4 to 48.2 pM and 10,355% to 19,484%, respectively, indicating that the study site was indeed a significant source of atmospheric NO despite extremely low NO ₂ ⁻ concentrations. NO concentrations correlated significantly with phytoplankton pigment concentrations, indicating that NO variability may be influenced by phytoplankton‐related processes rather than photochemical pathways alone. These findings highlight the need to further investigate the production mechanism of NO in nutrient‐poor oceanic environments.

The Antarctic region is a large component of the global climate system. While it is largely underrepresented in climate models due to the scarcity of in-situ data, the interactions between processes occurring mid- and high-latitude are even less investigated. Understanding the processes between the atmosphere, the ocean laying within the polar front is critical to assert the relevance of climate models and improve future climate predictions. The SOPHYAC-light (Responses of the Southern Ocean PHYtoplankton to climate changes, feedback to the Atmosphere -impact of Light) took place onboard of the research vessel Marion Dufresne during the Obs’Austral campaign 2025 between December 24th 2024 and February 5th 2025. Air-sea interaction process studies were performed using two Air-Sea Interface Tanks (ASIT, Sellegri et al. 2023) in the aim of quantifying realistic air-sea fluxes and their relation to seawater biochemical properties, as well as the impact of UV light on these processes. The twotanks, one as a control and the other UV shielded, were filled with 1 m3 of seawater each at 7 different locations of the Southern Ocean, between sub-tropical and sub-Antarctic regions along the ship track. The incubation time varied between 4 and 6 days with coordinated water sample coupled with continuous atmospheric sampling within the head space of the two ASITS, with measurements of chemical, physical & biological parameters. The atmospheric measurements were focused on the investigation of new particle formation, encompassing three mass spectrometers for the characterization of gas phase precursors of aerosols and nanoparticle size distribution. A first overview of the SOPHYAC results related to new particle formation purely driven by the marine environment and ecosystem across the tropical / polar transect will be presented at the conference.

Nitric oxide (NO) is an intermediate of various microbial nitrogen cycle processes, and the open-ocean and coastal areas are generally a source of NO to the atmosphere. However, our knowledge about its distribution and the main production processes in coastal areas and estuaries is rudimentary at best. To this end, dissolved NO concentrations were measured for the first time in surface waters along the lower Elbe Estuary and Port of Hamburg area in July 2021. The discrete surface water samples were analyzed using a chemiluminescence NO analyzer connected to a stripping unit. The NO concentrations ranged from below the limit of detection (9.1 pM) to 17.7 pM, averaging 12.5 pM, and were supersaturated in the surface layer of both the lower Elbe Estuary and the Port of Hamburg area, indicating that the study site was a source of NO to the atmosphere during the study period. On the basis of a comprehensive comparison of NO concentrations with parallel nutrient, oxygen, and nitrous oxide concentration measurements, we conclude that the observed distribution of dissolved NO most likely resulted from nitrification. In the Port of Hamburg, however, nitrifier denitrification and/or denitrification might also affect the NO distribution.

Nitric oxide (NO) is an intermediate of various microbial nitrogen cycle processes and the open ocean and coastal areas are generally a source of NO in the atmosphere. However, our knowledge about its distribution and the main production processes in coastal areas and estuaries is rudimentary at best. To this end, dissolved NO concentrations were measured for the first time in surface waters along the lower Elbe Estuary and Hamburg Port area in July 2021. The discrete surface water samples were analyzed using a chemiluminescence detection method. The NO concentrations ranged from below the limit of detection (9.1 × 10⁻¹² mol L⁻¹) to 17.7 × 10⁻¹² mol L⁻¹, averaging at 12.5 × 10⁻¹² mol L⁻¹ and were supersaturated in the surface layer of both the lower Elbe Estuary and the Hamburg Port area, indicating that the study site was a source of NO to the atmosphere during the study period. On the basis of a comprehensive comparison of NO concentrations with parallel nutrient, oxygen, and nitrous oxide concentration measurements, we conclude that the observed distribution of dissolved NO was most likely resulting from microbial nitrogen transformation processes, particularly nitrification in the coastal-brackish and limnic zones of the lower Elbe Estuary and nitrifier-denitrification in the Hamburg Port area.

Nitric oxide (NO) is an intermediate of various microbial nitrogen cycle processes and the open ocean and coastal areas are generally a source of NO in the atmosphere. However, our knowledge about its distribution and the main production processes in coastal areas and estuaries is rudimentary at best. To this end, dissolved NO concentrations were measured for the first time in surface waters along the lower Elbe Estuary and Hamburg Port area in July 2021. The discrete surface water samples were analyzed using a chemiluminescence detection method. The NO concentrations ranged from below the limit of detection (9.1 × 10⁻¹² mol L⁻¹) to 17.7 × 10⁻¹² mol L⁻¹, averaging at 12.5 × 10⁻¹² mol L⁻¹ and were supersaturated in the surface layer of both the lower Elbe Estuary and the Hamburg Port area, indicating that the study site was a source of NO to the atmosphere during the study period. On the basis of a comprehensive comparison of NO concentrations with parallel nutrient, oxygen, and nitrous oxide concentration measurements, we conclude that the observed distribution of dissolved NO was most likely resulting from microbial nitrogen transformation processes, particularly nitrification in the coastal-brackish and limnic zones of the lower Elbe Estuary and nitrifier-denitrification in the Hamburg Port area.

Nitric oxide (NO) is an intermediate of various microbial nitrogen cycle processes and the open ocean and coastal areas are generally a source of NO in the atmosphere. However, our knowledge about its distribution and the main production processes in coastal areas and estuaries is rudimentary at best. To this end, dissolved NO concentrations were measured for the first time in surface waters along the lower Elbe Estuary and Hamburg Port area in July 2021. The discrete surface water samples were analyzed using a chemiluminescence detection method. The NO concentrations ranged from below the limit of detection (9.1 × 10⁻¹² mol L⁻¹) to 17.7 × 10⁻¹² mol L⁻¹, averaging at 12.5 × 10⁻¹² mol L⁻¹ and were supersaturated in the surface layer of both the lower Elbe Estuary and the Hamburg Port area, indicating that the study site was a source of NO to the atmosphere during the study period. On the basis of a comprehensive comparison of NO concentrations with parallel nutrient, oxygen, and nitrous oxide concentration measurements, we conclude that the observed distribution of dissolved NO was most likely resulting from microbial nitrogen transformation processes, particularly nitrification in the coastal-brackish and limnic zones of the lower Elbe Estuary and nitrifier-denitrification in the Hamburg Port area.

Nitric oxide (NO) is an intermediate of various microbial nitrogen cycle processes and the open ocean and coastal areas are generally a source of NO in the atmosphere. However, our knowledge about its distribution and the main production processes in coastal areas and estuaries is rudimentary at best. To this end, dissolved NO concentrations were measured for the first time in surface waters along the lower Elbe Estuary and Hamburg Port area in July 2021. The discrete surface water samples were analyzed using a chemiluminescence detection method. The NO concentrations ranged from below the limit of detection (9.1 × 10⁻¹² mol L⁻¹) to 17.7 × 10⁻¹² mol L⁻¹, averaging at 12.5 × 10⁻¹² mol L⁻¹ and were supersaturated in the surface layer of both the lower Elbe Estuary and the Hamburg Port area, indicating that the study site was a source of NO to the atmosphere during the study period. On the basis of a comprehensive comparison of NO concentrations with parallel nutrient, oxygen, and nitrous oxide concentration measurements, we conclude that the observed distribution of dissolved NO was most likely resulting from microbial nitrogen transformation processes, particularly nitrification in the coastal-brackish and limnic zones of the lower Elbe Estuary and nitrifier-denitrification in the Hamburg Port area.

Nitric oxide (NO) is an intermediate of various microbial nitrogen cycle processes and the open ocean and coastal areas are generally a source of NO in the atmosphere. However, our knowledge about its distribution and the main production processes in coastal areas and estuaries is rudimentary at best. To this end, dissolved NO concentrations were measured for the first time in surface waters along the lower Elbe Estuary and Hamburg Port area in July 2021. The discrete surface water samples were analyzed using a chemiluminescence detection method. The NO concentrations ranged from below the limit of detection (9.1 × 10⁻¹² mol L⁻¹) to 17.7 × 10⁻¹² mol L⁻¹, averaging at 12.5 × 10⁻¹² mol L⁻¹ and were supersaturated in the surface layer of both the lower Elbe Estuary and the Hamburg Port area, indicating that the study site was a source of NO to the atmosphere during the study period. On the basis of a comprehensive comparison of NO concentrations with parallel nutrient, oxygen, and nitrous oxide concentration measurements, we conclude that the observed distribution of dissolved NO was most likely resulting from microbial nitrogen transformation processes, particularly nitrification in the coastal-brackish and limnic zones of the lower Elbe Estuary and nitrifier-denitrification in the Hamburg Port area.

Nitric oxide (NO) is an intermediate of various microbial nitrogen cycle processes and the open ocean and coastal areas are generally a source of NO in the atmosphere. However, our knowledge about its distribution and the main production processes in coastal areas and estuaries is rudimentary at best. To this end, dissolved NO concentrations were measured for the first time in surface waters along the lower Elbe Estuary and Hamburg Port area in July 2021. The discrete surface water samples were analyzed using a chemiluminescence detection method. The NO concentrations ranged from below the limit of detection (9.1 × 10⁻¹² mol L⁻¹) to 17.7 × 10⁻¹² mol L⁻¹, averaging at 12.5 × 10⁻¹² mol L⁻¹ and were supersaturated in the surface layer of both the lower Elbe Estuary and the Hamburg Port area, indicating that the study site was a source of NO to the atmosphere during the study period. On the basis of a comprehensive comparison of NO concentrations with parallel nutrient, oxygen, and nitrous oxide concentration measurements, we conclude that the observed distribution of dissolved NO was most likely resulting from microbial nitrogen transformation processes, particularly nitrification in the coastal-brackish and limnic zones of the lower Elbe Estuary and nitrifier-denitrification in the Hamburg Port area.

Nitric oxide (NO) is an intermediate of various microbial nitrogen cycle processes and the open ocean and coastal areas are generally a source of NO in the atmosphere. However, our knowledge about its distribution and the main production processes in coastal areas and estuaries is rudimentary at best. To this end, dissolved NO concentrations were measured for the first time in surface waters along the lower Elbe Estuary and Hamburg Port area in July 2021. The discrete surface water samples were analyzed using a chemiluminescence detection method. The NO concentrations ranged from below the limit of detection (9.1 × 10⁻¹² mol L⁻¹) to 17.7 × 10⁻¹² mol L⁻¹, averaging at 12.5 × 10⁻¹² mol L⁻¹ and were supersaturated in the surface layer of both the lower Elbe Estuary and the Hamburg Port area, indicating that the study site was a source of NO to the atmosphere during the study period. On the basis of a comprehensive comparison of NO concentrations with parallel nutrient, oxygen, and nitrous oxide concentration measurements, we conclude that the observed distribution of dissolved NO was most likely resulting from microbial nitrogen transformation processes, particularly nitrification in the coastal-brackish and limnic zones of the lower Elbe Estuary and nitrifier-denitrification in the Hamburg Port area.