Assessing the steady-state [*NO2] in environmental samples. Implication for aromatic photonitration processes induced by nitrate and nitrite.

Based on available literature data of [NO2-], steady-state [*OH], and *OH generation rate upon nitrate photolysis in environmental aqueous samples under sunlight, the steady-state [*NO2], could be calculated. Interestingly, one to two orders of magnitude more *NO2 would be formed in photochemical processes in atmospheric water droplets compared to transfer from the gas phase. The relative importance of nitrite oxidation compared to nitrate photolysis as an *NO2 source would be higher in atmospheric than in surface waters. The calculated levels of *NO2 could lead to substantial transformation of phenol into nitrophenols in both atmospheric and surface waters.