The heterogeneous hydrolysis of NO2 in laboratory systems and in outdoor and indoor atmospheres: An integrated mechanism

Abstract

The heterogeneous reaction of NO 2 with water on the surface of laboratory systems has been known for decades to generate HONO, a major source of OH that drives the formation of ozone and other air pollutants in urban areas and possibly in snowpacks. Previous studies have shown that the reaction is first order in NO 2 and in water vapor, and the formation of a complex between NO 2 and water at the air-water interface has been hypothesized as being the key step in the mechanism. We report data from long path FTIR studies in borosilicate glass reaction chambers of the loss of gaseous NO 2 and the formation of the products HONO, NO and N 2 O. Further FTIR studies were carried out to measure species generated on the surface during the reaction, including HNO 3 , N 2 O 4 and NO 2 + . We propose a new reaction mechanism in which we hypothesize that the symmetric form of the NO 2 dimer, N 2 O 4 , is taken up on the surface and isomerizes to the asymmetric form, ONONO 2 . The latter autoionizes to NO + NO 3 À , and it is this intermediate that reacts with water to generate HONO and surface-adsorbed HNO 3 . Nitric oxide is then generated by secondary reactions of HONO on the highly acidic surface. This new mechanism is discussed in the context of our experimental data and those of previous studies, as well as the chemistry of such intermediates as NO + and NO 2 + that is known to occur in solution. Implications for the formation of HONO both outdoors and indoors in real and simulated polluted atmospheres, as well as on airborne particles and in snowpacks, are discussed. A key aspect of this chemistry is that in the atmospheric boundary layer where human exposure occurs and many measurements of HONO and related atmospheric constituents such as ozone are made, a major substrate for this heterogeneous chemistry is the surface of buildings, roads, soils, vegetation and other materials. This area of reactions in thin films on surfaces (SURFACE ¼ Surfaces, Urban and Remote: Films As a Chemical Environment) has received relatively little attention compared to reactions in the gas and liquid phases, but in fact may be quite important in the chemistry of the boundary layer in urban areas.

Remarkably High Stability of Late Actinide Dioxide Cations: Extending Chemistry to Pentavalent Berkelium and Californium

“…[12] Am anifestation of the presence of water in the trap is surface-catalyzed hydrolysis of NO 2 to yield HNO 2 and HNO 3 . [13] The presence of HNO 2 was confirmed by its addition to PuO(NO 3 ) 3 À ,p roduced as described previously, [14] to yield Pu(OH)(NO 2 )(NO 3 ) 3 À .A lthough the presence of HNO 3 was not similarly demonstrated by the appearance of Pu(OH)(NO 3 ) 4 À ,t his negative result does not exclude HNO 3 as a possible reactant gas in the ion trap.…”

“…Each of the MO + was isolated by ejection of all other ions from the QIT andt hen exposed to an indeterminate but constantp ressure of NO 2 for reactiont imes ranging from 0.05 to 0.55 s. The resultsa re shown in Figure 1w here it is apparent that each of the five studied monoxide cations abstracted an oxygen atom to yield MO 2 + .T he formationo ft he dioxides occurs by O-atom abstraction from some neutrals pecies RO in the ion trap under thermal conditions:M O + + RO! MO 2 + + R. As noted below,a nd expected based on the presence of H 2 Oi nt he ion trap, [12,13] hydrolysis of NO 2 yielded HNO 2 ,a sd emonstrated by its addition [14] to PuO(NO 3 ) 3 À to yield Pu(OH)(NO 2 )(NO 3 ) À .I tc an be inferredt hat HNO 3 was also produced, [13] and it is known that O 2 is also present in the trap. [12] The bond dissociation energies (D) for abstraction of an Oatom from the various neutralR Om olecules (potentially)p resent in the ion trap are as follows (in kcal mol À1 ): [15] …”

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.…”

Catalytic Role for Water in the Atmospheric Production of ClNO

“…The proposed mechanism involves the asymmetric NO 2 dimer and NO + NO 3 -as key surface-bound intermediates. 9 Figure 1, for example, shows that a band due to ClNO (centered at 1805 cm -1 ) appears when HCl and water vapor are added to a reaction cell containing NO 2 (seen initially at ∼1600 cm -1 ) and high surface area silica. The reaction is essentially immediate under these conditions and results in the formation of ClNO in a yield of 47 ( 1% (2 s) relative to the amount of NO 2 consumed.…”

“…9,[12][13][14] This hydrolysis reaction merits computational studies for several reasons. First, nitrous acid Figure 1.…”