“…Most studies over the last decade have focused on photochemical pathways for HONO formation from urban areas, ice sheets, and plant leaves. − However, recently it has been suggested that the marine boundary layer (MBL) has significant daytime HONO, with the photoreduction of nitrate as a likely source. − Additionally, despite the fact that HONO photodissociates within the solar actinic spectral region, its daytime concentration, especially in the MBL, has been found to reach quasi-steady-state levels, suggesting daytime photolytic sources. ,,, Recent field studies have found that nitrate photolysis reactions are likely the main contributor of photochemical HONO formation in the marine boundary layer (MBL). − , The source of nitrate in the MBL comes from the displacement of chloride with nitrate in aged sea spray aerosols due to heterogeneous chemistry with gas-phase nitrogen oxides (NO 2 , HNO 3 , and N 2 O 5 ). , …”