Photochemical processing of diesel fuel emissions as a large secondary source of isocyanic acid (HNCO). Issue 8 (26th April 2016)

• Record Type: Journal Article
• Authors: Link, M. F.; Friedman, B.; Fulgham, R.; Brophy, P.; Galang, A.; Jathar, S. H.; Veres, P.; Roberts, J. M.; Farmer, D. K.
• Is Part Of: Geophysical research letters. Volume 43:Issue 8(2016)
• Page Start: 4033
• Page End: 4041
• Publication Date: 2016-04-26
• Subjects: isocyanic acid -- photochemistry -- diesel emissions; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1002/2016GL068207
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: 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. Key Points: Direct observation of a photochemical source of HNCO from diesel exhaust Secondary production of HNCO from diesel exhaust is more important after a day of atmospheric aging than the primary emission source Primary emissions and secondary formation of HNCO are higher for idle engine loads than active engine loads