Nitric Oxide in the Ocean : Discrete Measurements of Dissolved NO Concentration in the Lower Elbe Estuary and Port of Hamburg Area, Ria Formosa Lagoon, and Tropical North Atlantic Ocean
Nitric oxide (NO) is a short-lived atmospheric trace gas rapidly oxidized to nitrogen dioxide (NO₂), forming NOₓ (NO + NO₂), which contributes to photochemical smog, acid rain, and influences tropospheric ozone. Measuring dissolved NO in seawater is challenging due to its reactivity and short lifetime. Knowledge of its marine distribution and cycling remains limited. Known sources include nitrite photolysis and biological production by phytoplankton, macroalgae, and microbes. Consumption pathways are still largely unresolved. This study presents NO measurements from the lower Elbe Estuary and Port of Hamburg (July 2021), Ria Formosa Lagoon (April 2021), and the tropical North Atlantic Ocean (Dec 2021–Jan 2022), using a chemiluminescence NO analyzer with a stripping unit (Lutterbeck & Bange, 2015). These are among the few global datasets on oceanic NO. Reported concentrations from past studies vary (5.9–260 pM), with supersaturation from 100% to 10,000%. Early work (Zafiriou & McFarland, 1981) even recorded supersaturation up to 10⁴ in the Pacific. In this study, average concentrations ranged from 11.1 to 13.9 pM, with supersaturation from 172 to 12,016% and flux densities from 0.05 to 3.47 × 10⁻¹⁷ mol cm⁻² s⁻¹, reinforcing the view that oceans may act as a NO source. However, high spatial and temporal variability highlights the need for further research using high-resolution sampling, isotope tracers, and molecular tools to better define the ocean's role in atmospheric NOₓ budgets.
Preview
Rights
Use and reproduction:
Please note that individual components of the publication may be subject to other licensing or copyright conditions.