Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas
Isocyanic acid (HNCO), an acidic gas found in tobacco smoke, urban environments, and biomass-burning-affected 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 th...
| Main Authors: | , , , , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-07-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/8959/2017/acp-17-8959-2017.pdf |
| _version_ | 1818197143732617216 |
|---|---|
| author | S. H. Jathar C. Heppding M. F. Link D. K. Farmer A. Akherati M. J. Kleeman J. A. de Gouw J. A. de Gouw P. R. Veres P. R. Veres J. M. Roberts |
| author_facet | S. H. Jathar C. Heppding M. F. Link D. K. Farmer A. Akherati M. J. Kleeman J. A. de Gouw J. A. de Gouw P. R. Veres P. R. Veres J. M. Roberts |
| author_sort | S. H. Jathar |
| collection | DOAJ |
| description | Isocyanic acid (HNCO), an acidic gas found in tobacco smoke, urban
environments, and biomass-burning-affected 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<sup>−1</sup>) 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
daily-averaged 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. |
| first_indexed | 2024-12-12T01:45:18Z |
| format | Article |
| id | doaj.art-116f9d300cfe4e798d94e0cf681bce05 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-12T01:45:18Z |
| publishDate | 2017-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-116f9d300cfe4e798d94e0cf681bce052022-12-22T00:42:36ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242017-07-01178959897010.5194/acp-17-8959-2017Investigating diesel engines as an atmospheric source of isocyanic acid in urban areasS. H. Jathar0C. Heppding1M. F. Link2D. K. Farmer3A. Akherati4M. J. Kleeman5J. A. de Gouw6J. A. de Gouw7P. R. Veres8P. R. Veres9J. M. Roberts10Department of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523, USADepartment of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523, USADepartment of Chemistry, Colorado State University, Fort Collins, CO 80523, USADepartment of Chemistry, Colorado State University, Fort Collins, CO 80523, USADepartment of Mechanical Engineering, Colorado State University, Fort Collins, CO 80523, USADepartment of Civil and Environmental Engineering, University of California Davis, Davis, CA 95616, USANOAA Earth System Research Laboratory, Chemical Sciences Division, Boulder, CO 80305, USACooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80305, USANOAA Earth System Research Laboratory, Chemical Sciences Division, Boulder, CO 80305, USACooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80305, USANOAA Earth System Research Laboratory, Chemical Sciences Division, Boulder, CO 80305, USAIsocyanic acid (HNCO), an acidic gas found in tobacco smoke, urban environments, and biomass-burning-affected 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<sup>−1</sup>) 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 daily-averaged 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.https://www.atmos-chem-phys.net/17/8959/2017/acp-17-8959-2017.pdf |
| spellingShingle | S. H. Jathar C. Heppding M. F. Link D. K. Farmer A. Akherati M. J. Kleeman J. A. de Gouw J. A. de Gouw P. R. Veres P. R. Veres J. M. Roberts Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas Atmospheric Chemistry and Physics |
| title | Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas |
| title_full | Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas |
| title_fullStr | Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas |
| title_full_unstemmed | Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas |
| title_short | Investigating diesel engines as an atmospheric source of isocyanic acid in urban areas |
| title_sort | investigating diesel engines as an atmospheric source of isocyanic acid in urban areas |
| url | https://www.atmos-chem-phys.net/17/8959/2017/acp-17-8959-2017.pdf |
| work_keys_str_mv | AT shjathar investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas AT cheppding investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas AT mflink investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas AT dkfarmer investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas AT aakherati investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas AT mjkleeman investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas AT jadegouw investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas AT jadegouw investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas AT prveres investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas AT prveres investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas AT jmroberts investigatingdieselenginesasanatmosphericsourceofisocyanicacidinurbanareas |