Nitric acid photolysis on surfaces in low‐NO_x environments: Significant atmospheric implications

Abstract

.[1] Nitric acid (HNO 3 ) is the dominant end product of NO x (= NO + NO 2 ) oxidation in the troposphere, and its dry deposition is considered to be a major removal pathway for the atmospheric reactive nitrogen. Here we present both field and laboratory results to demonstrate that HNO 3 deposited on ground and vegetation surfaces may undergo effective photolysis to form HONO and NO x , 1 -2 orders of magnitude faster than in the gas phase and aqueous phase. With this enhanced rate, HNO 3 photolysis on surfaces may significantly impact the chemistry of the overlying atmospheric boundary layer in remote low-NO x regions via the emission of HONO as a radical precursor and the recycling of HNO 3 deposited on ground surfaces back to NO x .

The photolysis of ortho-nitrophenols: a new gas phase source of HONO

“…36,38,41,43,47 The measured HONO levels were significantly higher than the values predicted on the basis of the available knowledge about daytime sources and sinks of HONO. The experiments revealed the existence of a strong daytime source of HONO up to 60 times higher than the night time sources 43 and contributing up to 60% to the direct OH radical sources, 48 which was suggested to arise from the photolysis of adsorbed HNO 3 /nitrate 38,47,[49][50][51] or by heterogeneous photochemistry of NO 2 on organic substrates. [52][53][54] Recent work in our laboratory on different aspects of aromatic hydrocarbon photooxidation processes performed in the presence of OH-radical scavengers has revealed that OH radicals are generated during the photolysis of nitrophenols.…”

Hydrolysis of Organonitrate Functional Groups in Aerosol Particles

“…Handley et al (2007) observed that gas-phase nitric acid adsorbs and dissociates into a proton and a nitrate anion on dry, hydrophobic organic films at partial pressures below the saturation pressure of nitric acid, which suggests uptake of nitric acid on dry organic particles may occur. However, Zhou et al (2003) and Handley et al (2007) also demonstrated that the proton and nitrate ion are photolyzed under actinic radiation and evaporate to the gas phase. Therefore, the adsorbed nitric acid on dry particles is unlikely to be significant in these photo-oxidation experiments.…”

Measurements of nitrous acid (HONO) in urban area of Shanghai, China

“…This includes different surfaces (ground and aerosols) such as the photocatalytic conversion of NO 2 on mineral dust (Ndour et al 2008), the dark heterogeneous conversion of NO 2 on suspended soot particles (Ammann et al 1998;Arens et al 2001), the heterogeneous hydrolysis of NO 2 (Finlayson-Pitts et al 2003), the photosensitized reduction of NO 2 on organic surfaces (George et al 2005;Stemmler et al 2006), the photolysis of adsorbed nitric acid (HNO 3 ) (Zhou et al 2003) and nitrate (NO 3 − ) (Zhou et al 2001), the HNO 3 conversion on primary organic aerosols (Ziemba et al 2010) and from soilemitted nitrite (Su et al 2011). Direct emissions from combustion processes (i.e.…”