Vertical gradients of HONO, NOx and O3 in Santiago de Chile

Villena, Guillermo Lohmann; Kleffmann, Jörg; Kurtenbach, R.; Wiesen, Peter; Lissi, E. A.; Rubio, Marı́a A.; Croxatto, Giovanna; Rappenglück, Bernhard

doi:10.1016/j.atmosenv.2011.01.073

Cited by 84 publications

(102 citation statements)

References 25 publications

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“…This is a range that is similar to values found elsewhere (Lammel and Cape, 1996;Elshorbany et al, 2009;Villena et al, 2011). The HONO/NO x ratio shown in Figure 5 is primarily determined by emissions, removal processes, and transport of air masses that may contain different amounts of NO x and/or HONO.…”

Section: Resultssupporting

confidence: 66%

“…According to the EPA (2010b), the NO 2 /NO x emission ratio from gasoline driven vehicles rose from about 2.5% for car model years 1960-1980 to about 16% for car model years 1996 and younger. Relatively high NO 2 /NO x measured ratios of about 13% have also been found in recent studies (Villena et al, 2011), where diesel driven buses might have contributed significantly. Like that study, our study in particular included heavy-duty diesel trucks that frequented the highways.…”

Section: Resultsmentioning

confidence: 51%

“…The HONO/NO x ratio shown in Figure 5 is primarily determined by emissions, removal processes, and transport of air masses that may contain different amounts of NO x and/or HONO. However, it is noteworthy that HONO/NO x ratios during rush hour (about 2%) and around noontime (about $3.5-4%) are slightly higher than in environments where higher NO x mixing ratios were reported (e.g., Elshorbany et al, 2009;Villena et al, 2011). Table 5 shows all the observed compound ratios obtained at the measuring site during July 15-October 15, 2009, for morning rush hour times and separately for September 28, 2009, morning rush hours, which is used for model comparison.…”

Section: Resultsmentioning

confidence: 85%

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Radical precursors and related species from traffic as observed and modeled at an urban highway junction

Rappenglück

Lubertino

Alvarez

et al. 2013

Journal of the Air & Waste Management Association

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Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals and are believed to favor ozone formation significantly. Traffic emission data for both compounds are scarce and mostly outdated. A better knowledge of today's HCHO and HONO emissions related to traffic is needed to refine air quality models. Here the authors report results from continuous ambient air measurements taken at a highway junction in Houston, Texas, from July 15 to October 15, 2009. The observational data were compared with emission estimates from currently available mobile emission models (MOBILE6; MOVES [MOtor Vehicle Emission Simulator]). Observations indicated a molar carbon monoxide (CO) versus nitrogen oxides (NO x ) ratio of 6.01 AE 0.15 (r 2 ¼ 0.91), which is in agreement with other field studies. Both MOBILE6 and MOVES overestimate this emission ratio by 92% and 24%, respectively. For HCHO/CO, an overall slope of 3.14 AE 0.14 g HCHO/kg CO was observed. Whereas MOBILE6 largely underestimates this ratio by 77%, MOVES calculates somewhat higher HCHO/CO ratios (1.87) than MOBILE6, but is still significantly lower than the observed ratio. MOVES shows high HCHO/CO ratios during the early morning hours due to heavyduty diesel off-network emissions. The differences of the modeled CO/NO x and HCHO/CO ratios are largely due to higher NO x and HCHO emissions in MOVES (30% and 57%, respectively, increased from MOBILE6 for 2009), as CO emissions were about the same in both models. The observed HONO/NO x emission ratio is around 0.017 AE 0.0009 kg HONO/kg NO x which is twice as high as in MOVES. The observed NO 2 /NO x emission ratio is around 0.16 AE 0.01 kg NO 2 /kg NO x , which is a bit more than 50% higher than in MOVES. MOVES overestimates the CO/CO 2 emission ratio by a factor of 3 compared with the observations, which is 0.0033 AE 0.0002 kg CO/kg CO 2 . This as well as CO/NO x overestimation is coming from light-duty gasoline vehicles.Implications: Nitrous acid (HONO) and formaldehyde (HCHO) are important precursors for radicals that ultimately contribute to ozone formation. There still exist uncertainties in emission sources of HONO and HCHO and thus regional air quality modeling still tend to underestimate concentrations of free radicals in the atmosphere. This paper demonstrates that the latest U.S. Environmental Protection Agency (EPA) traffic emission model MOVES still shows significant deviations from observed emission ratios, in particular underestimation of HCHO/CO and HONO/NO x ratios. Improving the performance of MOVES may improve regional air quality modeling.

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Section: Resultssupporting

confidence: 66%

Section: Resultsmentioning

confidence: 51%

Section: Resultsmentioning

confidence: 85%

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Radical precursors and related species from traffic as observed and modeled at an urban highway junction

Rappenglück

Lubertino

Alvarez

et al. 2013

Journal of the Air & Waste Management Association

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“…Similarly, Sörgel et al (2011b) did not observe gradients in the lowest 25 m of a forest. In contrast, Villena et al (2011) found elevated levels of HONO at 6 m compared to 53 m altitude in a polluted urban area. Two aircraft observations have been reported.…”

Section: Introductionmentioning

confidence: 73%

“…Similarly, gas-phase sources in a well-mixed boundary layer should also, in principle, lead to a fairly uniform HONO vertical distribution. However, only a few observational studies have been performed to measure daytime HONO vertical profiles (Kleffmann, 2007;Zhang et al, 2009;Villena et al, 2011;Zhou et al, 2001;Häseler et al, 2009). The results from these studies are not conclusive.…”

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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Evidence for a nitrous acid (HONO) reservoir at the ground surface in Bakersfield, CA, during CalNex 2010

et al. 2014

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Measurements of HONO (g) were validated to be free of known interferences for wet chemical instrumentation. The accumulation of nitrite into particulate matter was found to be enhanced when gaseous mixing ratios of HONO (g) were highest. Reactive uptake of HONO (g) on to lofted dust and the ground surface, forming a reservoir, is a potential mechanism to explain these observations. The AIM-IC HONO (g) measurements were parameterized in a chemical model to calculate the ground surface daytime HONO (g) source strength at 4.5 m above the surface, found to be on the order of 1.27 ppb h À1, to determine the relative importance of a surface reservoir. If all deposited nighttime HONO (g) is reemitted the following day, up to 30% of the daytime HONO (g) source at CalNex-SJV may be accounted for. The observations of HONO (g) and NO 2 À (p) in Bakersfield, during CalNex, suggest a surface sink and source of HONO (g) . Extension of currently accepted unknown daytime HONO (g) source reactions to include a potential surface HONO (g) reservoir should therefore be sound, but quantitation of the relative contributions of each surface source toward daytime HONO (g) production remains to be resolved.

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Vertical gradients of HONO, NOx and O3 in Santiago de Chile

Cited by 84 publications

References 25 publications

Radical precursors and related species from traffic as observed and modeled at an urban highway junction

Radical precursors and related species from traffic as observed and modeled at an urban highway junction

Modeling of daytime HONO vertical gradients during SHARP 2009

Evidence for a nitrous acid (HONO) reservoir at the ground surface in Bakersfield, CA, during CalNex 2010

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