Implementation and Refinement of a Surface Model for Heterogeneous HONO Formation in a 3-D Chemical Transport Model (original) (raw)
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The photolysis of HONO is important for the atmospheric HO x (OH + HO 2) radical budget and ozone formation , especially in polluted air. Nevertheless, owing to the incomplete knowledge of HONO sources, realistic HONO mechanisms have not yet been implemented in global models. We investigated measurement data sets from 15 field measurement campaigns conducted in different countries worldwide. It appears that the HONO/NO x ratio is a good proxy predictor for HONO mixing ratios under different atmospheric conditions. From the robust relationship between HONO and NO x , a representative mean HONO/NO x ratio of 0.02 has been derived. Using a global chemistry-climate model and employing this HONO/NO x ratio, realistic HONO levels are simulated, being about one order of magnitude higher than the reference calculations that only consider the reaction OH + NO → HONO. The resulting enhancement of HONO significantly impacts HO x levels and photo-oxidation products (e.g, O 3 , PAN), mainly in polluted regions. Furthermore , the relative enhancements in OH and secondary products are higher in winter than in summer, thus enhancing the oxidation capacity in polluted regions, especially in winter when other photolytic OH sources are of minor importance. Our results underscore the need to improve the understanding of HONO chemistry and its representation in atmospheric models.
Contribution of HONO sources to the NO x/HO x/O 3 chemistry in the polluted boundary layer
The contribution of HONO photolysis to the primary production of OH radicals and the impact of HONO sources to the O 3 and NO x budgets has been investigated using a two-layer box model. Three sources of HONO were considered: direct emissions, heterogeneous production on the ground surface and heterogeneous production on the aerosol surface. We considered two scenarios representing typical urban and polluted rural area and simulations were conducted for both summer and winter conditions. For summertime conditions, HONO sources were found to have a slight impact on the NO x /HO x /O 3 concentration profiles, except for conditions favoring the formation of photochemical pollution episodes where it becomes significant. For wintertime conditions, HONO sources were found to be major contributors to the primary OH production, leading to major changes in the HO x and NO x budget all day long. r
Laboratory studies of sources of HONO in polluted urban atmospheres
Geophysical research letters, 2000
Laboratory studies reported here and in previous work show that the reaction of NO(g) with surface adsorbed HNO 3 may be a significant source of HONO in polluted urban atmospheres. If these laboratory studies can be extrapolated to ambient conditions, this heterogeneous reaction may generate HONO to about the same extent as the hydrolysis of NO on surfaces, which is greater than the heterogeneous 2 and water. It may also be involved in reaction of NO, NO 2 generating HONO in snowpacks, and important in reconciling the discrepancy between measured and modeled HNO/NO ratios in the troposphere. 3 13825-13832, 1999.
Impact of HONO sources on the performance of mesoscale air quality models
Atmospheric Environment, 2012
Nitrous acid (HONO) photolysis constitutes a primary source of OH in the early morning, which leads to changes in model gas-phase and particulate matter concentrations. However, state-of-the-art models of chemical mechanisms share a common representation of gas-phase chemistry leading to HONO that fails in reproducing the observed profiles. Hence, there is a growing interest in improving the definition of additional HONO sources within air quality models, i.e. direct emissions or heterogeneous reactions. In order to test their feasibility under atmospheric conditions, the WRF-ARW/HERMES/CMAQ modeling system is applied with high horizontal resolution (4 Â 4 km 2) to Spain for November 24e27, 2008. HONO modeled sources include: (1) direct emissions from on-road transport; NO 2 hydrolysis on aerosol and ground surfaces, the latter with (2) kinetics depending exclusively on available surfaces for reaction and (3) refined kinetics considering also relative humidity dependence; and (4) photoenhanced NO 2 reduction on ground surfaces. The DOMINO measurement campaign performed in El Arenosillo (Southern Spain) provides valuable HONO observations. Modeled HONO results are consistently below observations, even when the most effective scenario is assessed, corresponding to contributions of direct emissions and NO 2 hydrolysis with the simplest kinetics parameterization. With the additional sources of HONO, PM 2.5 predictions can be up to 14% larger in urban areas. Quantified impacts on secondary pollutants have to be taken as a low threshold, due to the proven underestimation of HONO levels. It is fundamental to improve HONO sources definition within air quality models, both for the scientific community and decision makers.
NH<sub>3</sub>-promoted hydrolysis of NO<sub>2</sub> induces explosive growth in HONO
Atmospheric Chemistry and Physics Discussions
The study of atmospheric nitrous acid (HONO), which is the primary source of OH radicals, is 14 crucial to atmospheric photochemistry and heterogeneous chemical processes. The heterogeneous 15 NO2 chemistry under haze conditions was pointed out to be one of the missing sources of HONO 16 on the North China Plain, producing sulfate and nitrate in the process. However, controversy exists 17 between various proposed mechanisms, mainly debating on whether SO2 directly takes part in the 18 HONO production process and what roles NH3 and the pH value play in it. In this paper, never 19 before seen explosive HONO production (maximum rate: 16 ppb/hour) was reported and evidence 20 was found for the first time in field measurements during fog episodes (usually with pH>5) and 21 haze episodes under high relative humidity (usually with pH<5), that NH3 was the key factor that 22 promoted the hydrolysis of NO2, leading to explosive growth of HONO and nitrate under both 23 high and lower pH conditions. The results also suggest that SO2 does not directly take part in the 24 HONO formation, but was indirectly oxidized upon the photolysis of HONO through subsequent 25 radical mechanisms. Aerosol hygroscopicity significantly increased with the rapid inorganic 26 secondary aerosol formation further promoting the HONO production. For future photochemical 27 and aerosol pollution abatement, it is crucial to introduce effective NH3 emission control measures, 28 since the NH3-promoted NO2 hydrolysis is a large daytime HONO source, releasing large amounts 29 of OH radicals upon photolysis, which will contribute largely to both atmospheric photochemistry 30 and secondary aerosol formation. 31 32 Atmos. Chem. Phys. Discuss., https://doi.1 Introduction 34 Nitrous acid (HONO) plays a vital role in atmospheric chemistry due to the fact that its 35 photolysis is a major source (Michoud et al., 2014;Kleffmann et al., 2005) of hydroxyl radical (OH) 36 which determines the atmospheric oxidative capacity and plays crucial role in tropospheric 37 chemistry in processes such as the ozone formation, the degradation of volatile organic compounds 38 and the secondary aerosol formation (Cheng et al., 2016;Wang et al., 2016b). Hence, the source 39 study of nitrous acid (HONO) is of crucial importance for the understanding of the tropospheric 40 chemistry, for chemistry and climate modelling and for developing effective pollution control 41 strategies (Lu et al., 2018). 42 The North China Plain (NCP) is troubled by the persistent complex air pollution with high 43 loadings of both photochemical pollutants and particulate pollution (Zheng et al., 2015;Ran et al., 44 2011) and the simultaneous mitigation of the two types of pollution has encountered trouble due 45 to the nonlinear dependence of ozone on NOx (Xing et al., 2018). Unknown daytime sources of 46 HONO caught attention during the past few years (Michoud et al., 2014;Liu et al., 2014;Su et al., 47 2011) and results from a recent study indicate that an additional missing source is required to 48 explain more than 50% of observed HONO concentration in the daytime in Western China (Huang 49 et al., 2017). Results from several recent studies demonstrate that intense heterogeneous 50 conversion of NO2 to HONO on particle surfaces might be a significant source of HONO (Liu et 51 al., 2014;Cui et al., 2018). 52 Two main HONO heterogeneous production pathways involving aerosol water and NO2 53 were proposed. In light of drastic decrease of solar radiation during severe haze events and rich 54 ammonia conditions on the NCP, the first pathway hypothesized that NO2 (g) dissolved in aerosol 55 water at aerosol pH > 5.5 rapidly formed HONO while oxidizing HSO3 -(aq) to sulfate. The 56 stoichiometry of this mechanism is as follows (Cheng et al., 2016;Wang et al., 2016a): 57 2NO2 (aq) + HSO3 -(aq) + H2O (l) => 2H + + HSO4 -(aq) + 2NO2 -(aq). (R1) 58 Based on this mechanism, good agreement between modelled and observed sulfate 59 formation rates were achieved. However, the assumption that the pH of ambient aerosols can reach 60 beyond 5.5 is a debatable issue. Results from several most recent studies indicate that the pH of 61 Atmos. Chem. Phys. Discuss., https://doi.3 ambient aerosols fall in the range of 3-5 in most cases (Ding et al., 2018;Liu et al., 2017a;Song et 62 al., 2018). Given this, it was proposed that HONO and NO2were produced in the hydrolysis 63 process of NO2, releasing OH radicals upon photolysis, which indirectly oxidize SO2 to sulfate (Li 64 et al., 2018b): 65 2NO2 (g) + H2O (l) => H + + NO3 -(aq) + HONO. (R2) 66 Results of Yabushita et al. (2009) suggest that anions greatly enhance the hydrolysis of 67 NO2 on water, and the NO2 uptake coefficients of R2 can be enhanced several orders of magnitude 68 by increasing electrolyte concentration. The ambient aerosol particles in the boundary layer are in 69 aqueous phase under high RH (Liu et al., 2017b) and the aerosol or fog water is not pure with 70 different dissolved anions (Wu et al., 2018;Lu et al., 2010). Therefore, HONO and nitrate formed 71 through this mechanism should be independent of aerosol acidity, and should be primarily affected 72 by the aerosol surface area density, aerosol liquid water content and NO2 concentration (Li et al., 73 2018b). Moreover, recent theoretical simulations have proposed a HONO formation mechanism 74 involving NO2 and water and have identified that NH3 can promote the hydrolysis of NO2 (Li et 75 al., 2018a) (R2). Despite of this, no direct evidence from field observations were available in this 76 paper to support their findings. 77 Although the proposed HONO formation mechanisms are all heterogeneous reactions of 78 NO2, the details of how SO2, pH and NH3 are involved in heterogeneous formation are still under 79 debate (Li et al., 2018b) and a clear mechanism is still missing in current models to explain both 80 the daytime concentration of observed HONO and the secondary inorganic aerosol formation. 81 Measurements of HONO are rare and simultaneous observations of HONO and aerosol physical 82 and chemical characteristics are lacking to thoroughly analyze or directly support the aerosol 83 heterogeneous HONO formation mechanisms involving NO2. In this paper, we present for the first 84 time simultaneous measurements of HONO, sulfate and nitrate as well as other precursor gases, 85 oxidants and meteorological parameters during both fog and haze episodes under high ambient 86 RH. Fog water pH is usually greater than 5.5 in eastern China (Safai et al., 2008;Lu et al., 2010), 87 while calculations in this work and previous studies collectively indicate a moderately acidic 88 condition (4<pH<5) for fine particles in northern China winter haze. The observational results 89 unveil that NH3 is the key factor that promotes the hydrolysis of NO2, resulting in explosive 90 formation of HONO, nitrate and sulfate. 91 Atmos. Chem. Phys. Discuss., https://doi.
Reactive Uptake of HONO to TiO 2 Surface: “Dark” Reaction
The Journal of Physical Chemistry A, 2012
The interaction of HONO with TiO 2 solid films was studied under dark conditions using a low pressure flow reactor (1−10 Torr) combined with a modulated molecular beam mass spectrometer for monitoring of the gaseous species involved. The reactive uptake of HONO to TiO 2 was studied as a function of HONO concentration ([HONO) 0 = (0.3−3.3) × 10 12 molecules cm −3 ), water concentration (RH = 3 × 10 −4 to 13%), and temperature (T = 275−320 K). TiO 2 surface deactivation upon exposure to HONO was observed. The measured initial uptake coefficient of HONO on TiO 2 surface was independent of the HONO concentration and showed slight negative temperature dependence (activation factor = −1405 ± 110 K). In contrast, the relative humidity (RH) was found to have a strong impact on the uptake coefficient: γ 0 = 1.8 × 10 −5 (RH) -0.63 (calculated using BET surface area, 40% uncertainty) at T = 300 K. NO 2 and NO were observed as products of the HONO reaction with TiO 2 surface with sum of their yields corresponding to nearly 100% of the nitrogen mass balance. The yields of the NO and NO 2 products were found to be 42 ± 7% and 60 ± 9%, respectively, independent of relative humidity, temperature, and concentration of HONO under experimental conditions used. The contribution of aerosol to the total HONO loss in the boundary layer (calculated with initial uptake data for HONO on TiO 2 surface) showed the unimportance of this process in the atmosphere. In addition, the diffusion coefficient of HONO in He was determined to be D HONO-He = 490 ± 50 Torr cm 2 s −1 at T = 300 K.
Journal of the Meteorological Society of Japan, 2022
Atmospheric nitrous oxide (N 2 O) contributes to global warming and stratospheric ozone depletion, so reducing uncertainty in estimates of emissions from different sources is important for climate policy. In this study, we simulate atmospheric N 2 O using an atmospheric chemistry-transport model (ACTM), and the results are first compared with the in situ measurements. Five combinations of known (a priori) N 2 O emissions due to natural soil, agricultural land, other human activities, and sea-air exchange are used. The N 2 O lifetime is 127.6 ± 4.0 yr in the control ACTM simulation (range indicates interannual variability). Regional N 2 O emissions are optimized using Bayesian inverse modeling for 84 partitions of the globe at monthly intervals, using measurements at 42 sites around the world covering 1997-2019. The best estimated global land and ocean emissions are 12.99 ± 0.22
The N 2 O 4 isomerization and the NO 2 dimerization play an important role in fundamental, high-energy materials and atmospheric and environmental chemistries. In particular, the N 2 O 4 molecule is a very important source of nitrous acids (HONO), which is the main source of OH radicals in the atmosphere. This subject has recently been present in several studies. 1À8 Finlayson-Pitts et al. 1 have proposed the following mechanism to better understand the N 2 O 4 hydrolysis: 2NO 2 ðgÞ T N 2 O 4 ðgÞ ð 1Þ N 2 O 4 ðgÞ T N 2 O 4 ðsurfaceÞ ð 2Þ N 2 O 4 ðsurfaceÞ f ONONO 2 ðsurfaceÞ ð 3Þ ONONO 2 ðsurfaceÞ f NO þ NO 3 À ðsurfaceÞ ð4Þ NO þ NO 3 À ðsurfaceÞ þ H 2 O f HONOðgÞ þ HNO 3 ðsurfaceÞ
Kinetics and Products of Heterogeneous Reaction of HONO with Fe 2 O 3 and Arizona Test Dust
Environmental Science & Technology, 2013
Kinetics and products of the reaction of HONO with solid films of Fe 2 O 3 and Arizona Test Dust (ATD) were investigated using a low pressure flow reactor (1 − 10 Torr) combined with a modulated molecular beam mass spectrometer. The reactive uptake of HONO was studied as a function of HONO concentration ([HONO] 0 = (0.6 − 15.0) × 10 12 molecules cm −3 ), relative humidity (RH = 3 × 10 −4 − 84.1%) and temperature (T = 275 − 320 K). Initial reactive uptake coefficients were found to be similar under dark conditions and in the presence of UV irradiation (J NO2 = 0.012 s −1 ) and independent of the HONO concentration and temperature. In contrast, the relative humidity (RH) was found to have a strong impact on the uptake coefficients: γ (ATD) = 3.8 × 10 −6 (RH) −0.61 and γ (Fe 2 O 3 ) = 1.7 × 10 −6 (RH) −0.62 (γ calculated with BET surface area, 30% conservative uncertainty). In both reactions of HONO studied, NO 2 and NO were observed as gaseous products with yields of (60 ± 9) and (40 ± 6) %, respectively, independent of relative humidity, temperature, concentration of HONO and UV irradiation intensity. The observed data point to minor importance of the HONO uptake on mineral aerosol compared with other known sinks of HONO in the atmosphere, which are its dry deposition and photolysis in night-time and during the day, respectively.