Nitric acid photolysis on forest canopy surface as a source for tropospheric nitrous acid

Zhou, Xianliang; Zhang, Ning; TerAvest, Michaela A.; Tang, David; Hou, Jian; Bertman, S. B.; Alaghmand, M.; Shepson, P. B.; Carroll, Mary Anne; Griffith, Stephen M.; Dusanter, Sébastien; Stevens, P. S.

doi:10.1038/ngeo1164

Cited by 226 publications

(269 citation statements)

References 22 publications

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“…These observed levels are substantially higher than reported observations from forest environments in North America (Ren et al, 2011;Zhou et al, 2011), where NO x Figure 2. The temporal variations of OH reactivity calculated from the observed data set at TRF (Fig.…”

Section: Observational Resultscontrasting

confidence: 52%

“…Ren et al (2011) reported 30-60 ppt of HONO at the Blodgett Forest research station in the western foothills of the Sierra Nevada in the late summer of 2007. Zhou et al (2011) also reported the similar levels of HONO (below 100 ppt) from the PROPHET forest, a mixed hardwood forest in northern Michigan (Pellston, MI). However, significantly higher HONO levels (∼ 200 ppt to 2 ppb) were reported by Li et al (2012) from a rural observational site in the Pearl River Delta region near Guangzhou, where comparable NO 2 levels with TRF were observed.…”

Section: Observational Resultsmentioning

confidence: 71%

“…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. Finally, HONO emission from soil bacteria is also proposed (Oswald et al, 2013).…”

Section: Observational Resultsmentioning

confidence: 99%

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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 Resultscontrasting

confidence: 52%

Section: Observational Resultsmentioning

confidence: 71%

Section: Observational Resultsmentioning

confidence: 99%

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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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“…These surfaces include those coated with phenols and aromatic ketones as proposed by George et al (2005) and humic acids and soil as suggested by Stemmler et al (2006Stemmler et al ( , 2007. Another proposed daytime HONO formation mechanism is the photolysis of surface adsorbed nitric acid (HNO 3 ) (Zhou et al, 2007;He et al, 2006;Beine et al, 2002;Dibb et al, 2002;Zhou et al, 2002Zhou et al, , 2003Zhou et al, , 2011. Both of these heterogeneous formation pathways, NO 2 conversion and photolysis of HNO 3 , can potentially occur on aerosol and ground surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…Flux measurements of HONO have been carried out to study the daytime sources of HONO. Zhou et al (2011) reported HONO fluxes in a forest canopy, with a peak flux at noon of 1 × 10 10 molec cm −2 s −1 . Another study by the same group measured HONO flux over arctic snow and reported maximum HONO fluxes of 1 × 10 9 molec cm −2 s −1 .…”

Section: Introductionmentioning

confidence: 99%

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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Urban measurements of atmospheric nitrous acid: A caveat on the interpretation of the HONO photostationary state

et al. 2013

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[1] Numerous studies infer the existence of an "unknown" daytime HONO source based on the assumption that HONO is at photostationary state (PSS). Secondary HONO production rate as high as 1.1 ppb hr À1 can be estimated from this approach, based on measurements made during the Study of Houston Atmospheric Radical Precursors campaign in May of 2009. We argue, however, that the PSS assumption might not have been valid because the transport time from nearby NO x emission sources to the measurement site was likely less than the time required for HONO in vehicle exhaust to reach PSS. Using a chemical box model, we demonstrate that there is initially net HONO formation as high levels of NO in exhaust react with ambient OH. Net production is followed by a period of net HONO loss dominated by photolysis that is sustained for several minutes to hours depending on time of day. The presence of relatively fresh exhaust in sampled air can partially, if not fully, account for the observed measurement PSS discrepancy. We also show that a large fraction of the observed nighttime increase in HONO/NO x ratio is explained by NO 2 oxidation. These results do not rule out the existence of an unexplained secondary HONO source but suggest that great care must be exercised when applying the PSS method to quantify its strength.

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Nitric acid photolysis on forest canopy surface as a source for tropospheric nitrous acid

Cited by 226 publications

References 22 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

Urban measurements of atmospheric nitrous acid: A caveat on the interpretation of the HONO photostationary state

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