Daytime HONO vertical gradients during SHARP 2009 in Houston, TX

Wong, Kam W.; Tsai, Catalina; Lefer, B. L.; Haman, C.; Grossberg, N.; Brune, William H.; Ren, Xinrong; Luke, Winston T.; Stutz, J.

doi:10.5194/acp-12-635-2012

Cited by 137 publications

(194 citation statements)

References 60 publications

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“…However, recently proposed HONO production mechanisms may be able to explain the higher levels in the East Asian megacity region. One is HONO production from NO 2 photo-excitation (Wong et al, 2012) as the region usually has high NO 2 concentrations. Zhou et al (2011) claimed that significant HONO could be generated from nitrate photolysis processes on forest canopy surface by presenting observational data from a hardwood forest in Pellston, MI.…”

Section: Observational Resultsmentioning

confidence: 99%

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

Kim

Lee³

et al. 2015

Atmos. Chem. Phys.

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Abstract. Rapid urbanization and economic development in East Asia in past decades has led to photochemical air pollution problems such as excess photochemical ozone and aerosol formation. Asian megacities such as Seoul, Tokyo, Shanghai, Guangzhou, and Beijing are surrounded by densely forested areas, and recent research has consistently demonstrated the importance of biogenic volatile organic compounds (VOCs) from vegetation in determining oxidation capacity in the suburban Asian megacity regions. Uncertainties in constraining tropospheric oxidation capacity, dominated by hydroxyl radical, undermine our ability to assess regional photochemical air pollution problems. We present an observational data set of CO, NO x , SO 2 , ozone, HONO, and VOCs (anthropogenic and biogenic) from Taehwa research forest (TRF) near the Seoul metropolitan area in early June 2012. The data show that TRF is influenced both by aged pollution and fresh biogenic volatile organic compound emissions. With the data set, we diagnose HO x (OH, HO 2 , and RO 2 ) distributions calculated using the University of Washington chemical box model (UWCM v2.1) with nearexplicit VOC oxidation mechanisms from MCM v3.2 (Master Chemical Mechanism). Uncertainty from unconstrained HONO sources and radical recycling processes highlighted in recent studies is examined using multiple model simulations with different model constraints. The results suggest that (1) different model simulation scenarios cause systematic differences in HO x distributions, especially OH levels (up to 2.5 times), and (2) radical destruction (HO 2 + HO 2 or HO 2 + RO 2 ) could be more efficient than radical recycling (RO 2 + NO), especially in the afternoon. Implications of the uncertainties in radical chemistry are discussed with respect to ozone-VOC-NO x sensitivity and VOC oxidation product formation rates. Overall, the NO x limited regime is assessed except for the morning hours (8 a.m. to 12 p.m. local standard time), but the degree of sensitivity can significantly vary depending on the model scenarios. The model results also suggest that RO 2 levels are positively correlated with oxygenated VOCs (OVOCs) production that is not routinely constrained by observations. These unconstrained OVOCs can cause higher-than-expected OH loss rates (missing OH reactivity) and secondary organic aerosol formation. The series of modeling experiments constrained by observations strongly urge observational constraint of the radical pool to enable precise understanding of regional photochemical pollution problems in the East Asian megacity region.

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Section: Observational Resultsmentioning

confidence: 99%

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

Kim

Lee³

et al. 2015

Atmos. Chem. Phys.

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“…However, recent field observations show that daytime HONO concentrations can be substantially higher than the theoretical steady-state mixing ratio, reaching up to a few hundred ppt in urban and rural areas Acker et al, 2006a;Zhou et al, 2007;Wong et al, 2012). These elevated daytime HONO mixing ratios indicate the presence of unknown HONO formation mechanisms, which make HONO also a significant OH precursor throughout the day.…”

Section: Introductionmentioning

confidence: 98%

“…The retrieved mixing ratios were horizontally averaged between the Moody Tower and downtown Houston and vertically averaged over the LP-DOAS height intervals: lower (20-70 m), middle (70-130 m), and upper (130-300 m). Details of the experiment and data analysis are described in Wong et al (2012) and references therein. Our analysis will focus on the same sunny days as outlined in Wong et al (2012): 21 April, 17 and 18 May.…”

Section: Methodsmentioning

confidence: 99%

“…Analysis of the observational data of HONO, NO 2 and HONO/NO 2 ratios showed the presence of a photolytic HONO source, which exhibited a dependence on NO 2 concentrations and solar irradiance. The conversion of NO 2 to HONO was most likely occurring on the ground, rather than on aerosol or in the gas-phase (Wong et al, 2012). Here we will further expand this analysis by using a 1-D atmospheric chemistry and transport model to understand the observed vertical profiles of HONO, NO 2 and HONO/NO 2 ratios in Houston, TX.…”

Section: K W Wong Et Al: Modeling Of Daytime Hono Vertical Gradienmentioning

confidence: 99%

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Modeling of daytime HONO vertical gradients during SHARP 2009

et al. 2013

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Nitrous acid (HONO) acts as a major precursor of the hydroxyl radical (OH) in the urban atmospheric boundary layer in the morning and throughout the day. Despite its importance, HONO formation mechanisms are not yet completely understood. It is generally accepted that conversion of NO₂ on surfaces in the presence of water is responsible for the formation of HONO in the nocturnal boundary layer, although the type of surface on which the mechanism occurs is still under debate. Recent observations of higher than expected daytime HONO concentrations in both urban and rural areas indicate the presence of unknown daytime HONO source(s). Various formation pathways in the gas phase, and on aerosol and ground surfaces have been proposed to explain the presence of daytime HONO. However, it is unclear which mechanism dominates and, in the cases of heterogeneous mechanisms, on which surfaces they occur.

Vertical concentration profiles of HONO and its precursors can help in identifying the dominant HONO formation pathways. In this study, daytime HONO and NO₂ vertical profiles, measured in three different height intervals (20–70, 70–130, and 130–300 m) in Houston, TX, during the 2009 Study of Houston Atmospheric Radical Precursors (SHARP) are analyzed using a one-dimensional (1-D) chemistry and transport model. Model results with various HONO formation pathways suggested in the literature are compared to the the daytime HONO and HONO/NO₂ ratios observed during SHARP. The best agreement of HONO and HONO/NO₂ ratios between model and observations is achieved by including both a photolytic source of HONO at the ground and on the aerosol. Model sensitivity studies show that the observed diurnal variations of the HONO/NO₂ ratio are not reproduced by the model if there is only a photolytic HONO source on aerosol or in the gas phase from NO₂^* + H₂O. Further analysis of the formation and loss pathways of HONO shows a vertical dependence of HONO chemistry during the day. Photolytic HONO formation at the ground is the major formation pathway in the lowest 20 m, while a combination of gas-phase, photolytic formation on aerosol, and vertical transport is responsible for daytime HONO between 200–300 m a.g.l. HONO removal is dominated by vertical transport below 20 m and photolysis between 200–300 m a.g.l

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“…It was suggested that HONO arises from the photolysis of nitric acid and nitrate or by heterogeneous photochemistry of NO 2 on organic substrates and soot (Zhou et al, 2001(Zhou et al, , 2002(Zhou et al, and 2003Villena et al, 2011;Ramazan et al, 2004;George et al, 2005;Sosedova et al, 2011;Monge et al, 2010;Han et al, 2016). Stemmler et al (2006Stemmler et al ( , 2007 found HONO formation on light-activated humic acid, and field studies showed that HONO formation correlates with aerosol surface area, NO 2 and solar radiation (Su et al, 2008;Reisinger, 2000;Costabile et al, 2010;Wong et al, 2012;Sörgel et al, 2015) and is increased during foggy periods (Notholt et al, 1992). Another proposed source of HONO is the soil, where it has been found to be co-emitted with NO by soil biological activities (Oswald et al, 2013;Su et al, 2011;Weber et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

Light-induced protein nitration and degradation with HONO emission

et al. 2017

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Abstract. Proteins can be nitrated by air pollutants (NO 2 ), enhancing their allergenic potential. This work provides insight into protein nitration and subsequent decomposition in the presence of solar radiation. We also investigated lightinduced formation of nitrous acid (HONO) from protein surfaces that were nitrated either online with instantaneous gas-phase exposure to NO 2 or offline by an efficient nitration agent (tetranitromethane, TNM). Bovine serum albumin (BSA) and ovalbumin (OVA) were used as model substances for proteins. Nitration degrees of about 1 % were derived applying NO 2 concentrations of 100 ppb under VIS/UV illuminated conditions, while simultaneous decomposition of (nitrated) proteins was also found during long-term (20 h) irradiation exposure. Measurements of gas exchange on TNMnitrated proteins revealed that HONO can be formed and released even without contribution of instantaneous heterogeneous NO 2 conversion. NO 2 exposure was found to increase HONO emissions substantially. In particular, a strong dependence of HONO emissions on light intensity, relative humidity, NO 2 concentrations and the applied coating thickness was found. The 20 h long-term studies revealed sustained HONO formation, even when concentrations of the intact (nitrated) proteins were too low to be detected after the gas exchange measurements. A reaction mechanism for the NO 2 conversion based on the Langmuir-Hinshelwood kinetics is proposed.

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Daytime HONO vertical gradients during SHARP 2009 in Houston, TX

Cited by 137 publications

References 60 publications

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

Modeling of daytime HONO vertical gradients during SHARP 2009

Light-induced protein nitration and degradation with HONO emission

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