Reactive nitrogen compounds (RNCs) in exhaust of advanced PM–NOx abatement technologies for future diesel applications

Heeb, Norbert V.; Zimmerli, Yan; Czerwiński, Jan; Schmid, Peter; Zennegg, Markus; Haag, Regula; Seiler, Cornelia; Wichser, Adrian; Ulrich, Andrea; Honegger, Peter; Zeyer, Kerstin; Emmenegger, Lukas; Mosimann, Thomas; Kasper, Markus; Mayer, Andreas

doi:10.1016/j.atmosenv.2011.02.013

Cited by 39 publications

(76 citation statements)

References 36 publications

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“…This allowed the SCRequipped diesel engine to meet and exceed the most recent EPA Tier 4 emission standard of ∼ 1.6 g of NO x kg fuel −1 (or 0.4 g of NO x kW h −1 ). Similar to earlier work (Wentzell et al, 2013;Heeb et al, 2012Heeb et al, , 2011Suarez-Bertoa and Astorga, 2016), we observed HNCO when no NH 3 was injected, implying that the HNCO was produced either in the engine cylinder or in the aftertreatment devices upstream of the SCR (DOC + DPF). For six of the seven experiments performed with diesel fuel, HNCO emissions were reduced by 5-40 % with increasing NH 3 injections.…”

Section: No X and Hnco Emission Factorssupporting

confidence: 76%

“…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: 99%

“…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. c Roberts et al (2011). lated in Table S1 and the cumulative distribution function for the HNCO : CO data is show in Fig.…”

Section: Chemical Transport Modelingmentioning

confidence: 99%

“…Heeb et al (Heeb et al, 2011 performed experiments on an on-road diesel engine and found an order-of-magnitude increase in HNCO emissions with the SCR system engaged, implying that SCR systems could potentially be a source for HNCO. However, Heeb et al (Heeb et al, 2011(Heeb et al, , 2012 used an offline technique to measure HNCO, which lacks the time resolution and sensitivity found in online mass spectrometry instrumentation. To date, there has only been a single study that has used a large-scale model to simulate ambient concentrations of HNCO from biomass burning and biofuel combustion.…”

Section: Introductionmentioning

confidence: 99%

“…Since SCR systems produce HNCO as an intermediate product, they have been implicated as an atmospheric source of HNCO (Roberts et al, 2011). Heeb et al (Heeb et al, 2011 performed experiments on an on-road diesel engine and found an order-of-magnitude increase in HNCO emissions with the SCR system engaged, implying that SCR systems could potentially be a source for 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: No X and Hnco Emission Factorssupporting

confidence: 76%

Section: Chemical Transport Modelingmentioning

confidence: 99%

Section: Chemical Transport Modelingmentioning

confidence: 99%

Section: Introductionmentioning

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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New insights into atmospheric sources and sinks of isocyanic acid, HNCO, from recent urban and regional observations

et al. 2014

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Isocyanic acid (HNCO) has only recently been measured in the ambient atmosphere, and many aspects of its atmospheric chemistry are still uncertain. HNCO was measured during three diverse field campaigns: California Nexus-Research at the Nexus of Air Quality and Climate Change (CalNex 2010) at the Pasadena ground site, Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT 2011) at the Boulder Atmospheric Observatory (BAO) in Weld County, CO, and Biofuel Crops emission of Ozone precursors intensive (BioCORN 2011), in a cornfield NW of Fort Collins, CO. Mixing ratios varied from below detection limit (~0.003 ppbv) to over 1.2 ppbv during a period when agricultural burning impacted the BAO Tower site. Urban areas, such as the CalNex 2010 Pasadena site, appear to have both primary (combustion) and secondary (photochemical) sources of HNCO, 50 ± 9%, and 33 ± 12%, respectively, while primary sources were responsible for the large mixing ratios of HNCO observed during the wintertime NACHTT study in suburban Colorado. Isocyanic acid during the BioCORN study in rural NE Colorado was closely correlated to ozone and therefore likely photochemically produced as a secondary product from amines or formamide. The removal of HNCO from the lower atmosphere is thought to be due to deposition, as common gas phase loss processes of photolysis and reactions with hydroxyl radicals, are slow. These ambient measurements are consistent with some HNCO deposition, which was evident at night at these surface sites.

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Cloud partitioning of isocyanic acid (HNCO) and evidence of secondary source of HNCO in ambient air

Zhao

Lee

Wentzell

et al. 2014

Geophysical Research Letters

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Although isocyanic acid (HNCO) may cause a variety of health issues via protein carbamylation and has been proposed as a key compound in smoke‐related health issues, our understanding of the atmospheric sources and fate of this toxic compound is currently incomplete. To address these issues, a field study was conducted at Mount Soledad, La Jolla, CA, to investigate partitioning of HNCO to clouds and fogs using an Acetate Chemical Ionization Mass Spectrometer coupled to a ground‐based counterflow virtual impactor. The first field evidence of cloud partitioning of HNCO is presented, demonstrating that HNCO is dissolved in cloudwater more efficiently than expected based on the effective Henry's law solubility. The measurements also indicate evidence for a secondary, photochemical source of HNCO in ambient air at this site.

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Reactive nitrogen compounds (RNCs) in exhaust of advanced PM–NOx abatement technologies for future diesel applications

Cited by 39 publications

References 36 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

New insights into atmospheric sources and sinks of isocyanic acid, HNCO, from recent urban and regional observations

Cloud partitioning of isocyanic acid (HNCO) and evidence of secondary source of HNCO in ambient air

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