Real-Time Emission Factor Measurements of Isocyanic Acid from Light Duty Gasoline Vehicles

Brady, James M.; Crisp, T. A.; Collier, Sonya; Kuwayama, Toshihiro; Forestieri, Sara D.; Perraud, Véronique; Zhang, Qi; Kleeman, Michael J.; Cappa, Christopher D.; Bertram, Timothy H.

doi:10.1021/es504354p

Cited by 38 publications

(68 citation statements)

References 26 publications

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“…Wentzell et al (2013) measured tailpipe emissions of HNCO from an on-road diesel engine but did not conclusively point to the source (incylinder or aftertreatment) of the HNCO. The HNCO emissions were comparable to those from LDGVs measured by Brady et al (2014) but varied substantially (order of magnitude or more) with the drive cycle and possibly with the coemitted NO x emissions. Suarez-Bertoa and Astorga (2016) have measured tailpipe emissions of HNCO from a suite of modern on-road gasoline and diesel vehicles and found that the gasoline vehicles and newer diesel vehicles produced more HNCO than modern-day diesel vehicles.…”

Section: Introductionmentioning

confidence: 55%

“…Since we are modeling an episode prior to when diesel engines were required to have a DOC, we have only used non-DOC data to calculate low and high estimates for HNCO : CO ratios. Based on this work, and that of Link et al (2016), Heeb and coworkers (Heeb et al, 2011(Heeb et al, , 2012, and Wentzell et al (2013), we loosely calculated a lower bound HNCO : CO ratio of ∼ 0.001 that reflected diesel engine operation at lower engine loads and a higher HNCO : CO ratio of ∼ 0.01 that reflected diesel engine operation at higher engine loads; the HNCO : CO data from all sources are tabu- Brady et al (2014). b This work, Link et al (2016), and Heeb et al (2011.…”

Section: Chemical Transport Modelingmentioning

confidence: 96%

“…The ToF duty cycle was set to 16 kHz and data were acquired at 1 Hz resolution. A cross-calibration method was used to quantify HNCO similar to that described 8962 S. H. Jathar et al: Investigating diesel engines as an atmospheric source of isocyanic acid in Brady et al (2014). The primary assumption of the crosscalibration method was that the ratio of formic acid sensitivity to HNCO sensitivity would remain the same between the two instruments operated under similar voltage settings as described in Eq.…”

Section: Laboratory Experimentsmentioning

confidence: 99%

“…Previous HNCO studies on natural, biomass burning sources have been performed by Roberts et al (2011) and Coggon et al (2016). Brady et al (2014) measured tailpipe emissions of HNCO from eight light-duty gasoline vehicles (LDGVs) and suggested that HNCO emissions from LDGVs were not a result of incylinder combustion but rather a result of CO-and NO xdependent chemistry in the aftertreatment device, namely the three-way catalytic converter. Wentzell et al (2013) measured tailpipe emissions of HNCO from an on-road diesel engine but did not conclusively point to the source (incylinder or aftertreatment) of the HNCO.…”

Section: Introductionmentioning

confidence: 99%

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Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas

et al. 2017

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Abstract. Isocyanic acid (HNCO), an acidic gas found in tobacco smoke, urban environments, and biomass-burningaffected regions, has been linked to adverse health outcomes. Gasoline-and diesel-powered engines and biomass burning are known to emit HNCO and hypothesized to emit precursors such as amides that can photochemically react to produce HNCO in the atmosphere. Increasingly, diesel engines in developed countries like the United States are required to use selective catalytic reduction (SCR) systems to reduce tailpipe emissions of oxides of nitrogen. SCR chemistry is known to produce HNCO as an intermediate product, and SCR systems have been implicated as an atmospheric source of HNCO. In this work, we measure HNCO emissions from an SCR system-equipped diesel engine and, in combination with earlier data, use a three-dimensional chemical transport model (CTM) to simulate the ambient concentrations and source/pathway contributions to HNCO in an urban environment. Engine tests were conducted at three different engine loads, using two different fuels and at multiple operating points. HNCO was measured using an acetate chemical ionization mass spectrometer. The diesel engine was found to emit primary HNCO (3-90 mg kg fuel −1 ) but we did not find any evidence that the SCR system or other aftertreatment devices (i.e., oxidation catalyst and particle filter) produced or enhanced HNCO emissions. The CTM predictions compared well with the only available observational datasets for HNCO in urban areas but underpredicted the contribution from secondary processes. The comparison implied that diesel-powered engines were the largest source of HNCO in urban areas. The CTM also predicted that dailyaveraged concentrations of HNCO reached a maximum of ∼ 110 pptv but were an order of magnitude lower than the 1 ppbv level that could be associated with physiological effects in humans. Precursor contributions from other combustion sources (gasoline and biomass burning) and wintertime conditions could enhance HNCO concentrations but need to be explored in future work.

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Section: Introductionmentioning

confidence: 55%

Section: Chemical Transport Modelingmentioning

confidence: 96%

Section: Laboratory Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas

et al. 2017

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“…HNCO mixing ratios were possibly influenced by additional sources, including traffic, ONG wells, and industrial activity. Traffic exhaust is a primary emission source of HNCO (Brady et al, 2014;Link et al, 2016), but the lack of a morning rush-hour peak or correlation with CO suggests that it was not a strong primary source of HNCO at the site (Fig. 2).…”

Section: Isocyanic Acidmentioning

confidence: 99%

Tropospheric sources and sinks of gas-phase acids in the Colorado Front Range

et al. 2018

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Abstract. We measured organic and inorganic gas-phase acids in the Front Range of Colorado to better understand their tropospheric sources and sinks using a high-resolution time-of-flight chemical ionization mass spectrometer. Measurements were conducted from 4 to 13 August 2014 at the Boulder Atmospheric Observatory during the Front Range Air Pollution and Photochemistry Éxperiment. Diurnal increases in mixing ratios are consistent with photochemical sources of HNO 3 , HNCO, formic, propionic, butyric, valeric, and pyruvic acid. Vertical profiles taken on the 300 m tower demonstrate net surface-level emissions of alkanoic acids, but net surface deposition of HNO 3 and pyruvic acid. The surface-level alkanoic acid source persists through both day and night, and is thus not solely photochemical. Reactions between O 3 and organic surfaces may contribute to the surface-level alkanoic acid source. Nearby traffic emissions and agricultural activity are a primary source of propionic, butyric, and valeric acids, and likely contribute photochemical precursors to HNO 3 and HNCO. The combined diel and vertical profiles of the alkanoic acids and HNCO are inconsistent with dry deposition and photochemical losses being the only sinks, suggesting additional loss mechanisms.

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Photochemical processing of diesel fuel emissions as a large secondary source of isocyanic acid (HNCO)

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Friedman

Fulgham

et al. 2016

Geophysical Research Letters

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Isocyanic acid (HNCO) is a well‐known air pollutant that affects human health. Biomass burning, smoking, and combustion engines are known HNCO sources, but recent studies suggest that secondary production in the atmosphere may also occur. We directly observed photochemical production of HNCO from the oxidative aging of diesel exhaust during the Diesel Exhaust Fuel and Control experiments at Colorado State University using acetate ionization time‐of‐flight mass spectrometry. Emission ratios of HNCO were enhanced, after 1.5 days of simulated atmospheric aging, from 50 to 230 mg HNCO/kg fuel at idle engine operating conditions. Engines operated at higher loads resulted in less primary and secondary HNCO formation, with emission ratios increasing from 20 to 40 mg HNCO/kg fuel under 50% load engine operating conditions. These results suggest that photochemical sources of HNCO could be more significant than primary sources in urban areas.

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Real-Time Emission Factor Measurements of Isocyanic Acid from Light Duty Gasoline Vehicles

Cited by 38 publications

References 26 publications

Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas

Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas

Tropospheric sources and sinks of gas-phase acids in the Colorado Front Range

Photochemical processing of diesel fuel emissions as a large secondary source of isocyanic acid (HNCO)

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