Continuous Chemiluminescence Measurements of Dissolved Nitric Oxide (NO) and Nitrogen Dioxide (NO<sub>2</sub>) in the Ocean Surface Layer of the East China Sea
Ye Tian, Keke Wang, Gui‐Peng Yang, Peifeng Li, Chun‐Ying Liu, Riel Carlo O. Ingeniero, Hermann W. Bange
Abstract
Nitric oxide (NO) is a short-lived intermediate of the oceanic nitrogen cycle, and it is produced by biological and photochemical processes in the ocean. Nitrogen dioxide (NO2) is a reactive atmospheric compound which has not been determined in the ocean so far. Here, we present the setup and validation of a novel continuous underway measurement system to measure dissolved NO and NO2 in the surface ocean. The system consists of a seawater/gas equilibration component coupled to a chemiluminescence detector. It was successfully deployed during a 12 day cruise to the East China Sea in May 2018. Dissolved NO and NO2 surface concentrations ranged from <limit of detection (LOD) to 98 × 10–12 mol L–1 and <LOD to 83 × 10–12 mol L–1, respectively. The ECS was supersaturated with NO but significantly undersaturated with NO2, indicating that the surface waters were a source for atmospheric NO but a sink for atmospheric NO2 at the time of our measurements.