Measurements of gas phase acids in diesel exhaust: a relevant source of HNCO?

Gas-phase acids in light duty diesel (LDD) vehicle exhaust were measured using chemical ionization mass spectrometry (CIMS). Fuel based emission factors (EF) and NOx ratios for these species were determined under differing steady state engine operating conditions. The derived HONO and HNO3 EFs agree well with literature values, with HONO being the single most important acidic emission. Of particular importance is the quantification of the EF for the toxic species, isocyanic acid (HNCO). The emission factors for HNCO ranged from 0.69 to 3.96 mg kgfuel(-1), and were significantly higher than previous biomass burning emission estimates. Further ambient urban measurements of HNCO demonstrated a clear relationship with the known traffic markers of benzene and toluene, demonstrating for the first time that urban commuter traffic is a source of HNCO. Estimates based upon the HNCO-benzene relationship indicate that upward of 23 tonnes of HNCO are released annually from commuter traffic in the Greater Toronto Area, far exceeding the amount possible from LDD alone. Nationally, 250 to 770 tonnes of HNCO may be emitted annually from on-road vehicles, likely representing the dominant source of exposure in urban areas, and with emissions comparable to that of biomass burning.

[1]  P. Carlier,et al.  Carboxylic acids in the troposphere, occurrence, sources, and sinks: A review , 1996 .

[2]  L. E. Trimble,et al.  Synthesis of Isocyanic Acid from Nitric Oxide over Palladium and Iridium Catalysts , 1978, Science.

[3]  A. N. Strachan,et al.  Preparation and properties of isocyanic acid , 1982 .

[4]  M. Elsener,et al.  Oxidation of Diesel-Generated Volatile Organic Compounds in the Selective Catalytic Reduction Process , 1998 .

[5]  E. Dabek-Zlotorzynska,et al.  Determination of low-molecular-weight carboxylic acids in the ambient air and vehicle emissions: a review , 2000, Fresenius' journal of analytical chemistry.

[6]  O. Kröcher,et al.  An ammonia and isocyanic acid measuring method for soot containing exhaust gases , 2005 .

[7]  D. Trimm,et al.  The Formation of Isocyanic Acid (HNCO) by Reaction of NO, CO, and H2over Pt/SiO2and Its Hydrolysis on Alumina , 1996 .

[8]  R. Gorse,et al.  Nitric acid in diesel exhaust , 1983 .

[9]  J. D. de Gouw,et al.  Measurements of volatile organic compounds in the earth's atmosphere using proton-transfer-reaction mass spectrometry. , 2007, Mass spectrometry reviews.

[10]  Jan Czerwinski,et al.  Reactive nitrogen compounds (RNCs) in exhaust of advanced PM–NOx abatement technologies for future diesel applications , 2011 .

[11]  M. Tazerout,et al.  Organic acids emissions from natural-gas-fed engines , 2000 .

[12]  Michael J Kleeman,et al.  Measurement of emissions from air pollution sources. 5. C1-C32 organic compounds from gasoline-powered motor vehicles. , 2002, Environmental science & technology.

[13]  Ulrich Platt,et al.  Investigations of emissions and heterogeneous formation of HONO in a road traffic tunnel , 2001 .

[14]  Liisa Pirjola,et al.  Emissions of fine particles, NOx, and CO from on-road vehicles in Finland , 2005 .

[15]  C. K. Lee,et al.  Kinetics of the carbamylation of the amino groups of sickle cell hemoglobin by cyanate. , 1973, The Journal of biological chemistry.

[16]  E. Topol,et al.  Protein carbamylation links inflammation, smoking, uremia and atherogenesis , 2007, Nature Medicine.

[17]  M. Yassine,et al.  Development of a hydrophilic interaction liquid chromatography-mass spectrometry method for detection and quantification of urea thermal decomposition by-products in emission from diesel engine employing selective catalytic reduction technology. , 2012, Journal of chromatography. A.

[18]  I. R. Burling,et al.  Measurements of gas‐phase inorganic and organic acids from biomass fires by negative‐ion proton‐transfer chemical‐ionization mass spectrometry , 2010 .

[19]  I. R. Burling,et al.  Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions , 2010 .

[20]  Shao-Meng Li,et al.  Condensational uptake of semivolatile organic compounds in gasoline engine exhaust onto pre-existing inorganic particles , 2011 .

[21]  N. W. Cant,et al.  The Reduction of NO by CO in the presence of water vapour on supported platinum catalysts : formation of isocyanic acid (HNCO) and ammonia , 2003 .

[22]  I. R. Burling,et al.  Isocyanic acid in the atmosphere and its possible link to smoke-related health effects , 2011, Proceedings of the National Academy of Sciences.

[23]  E. Zervas,et al.  C1-C5 organic acid emissions from an SI engine: influence of fuel and air/fuel equivalence ratio. , 2001, Environmental science & technology.

[24]  Efthimios Zervas,et al.  Emission of specific pollutants from a compression ignition engine. Influence of fuel hydrotreatment and fuel/air equivalence ratio , 2001 .

[25]  D. Trimm,et al.  Formation of isocyanic acid during the reaction of mixtures of NO, CO and H2 over supported platinum catalysts , 1995 .

[26]  L. Graham,et al.  Capillary electrophoresis determinative and GC-MS confirmatory method for water-soluble organic acids in airborne particulate matter and vehicle emission. , 2005, Journal of separation science.

[27]  J. D. de Gouw,et al.  Evidence of rapid production of organic acids in an urban air mass , 2011 .

[28]  M. Zahniser,et al.  Development of negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS) for the measurement of gas-phase organic acids in the atmosphere , 2008 .

[29]  D. Siebers,et al.  Removal of nitric oxide from exhaust gas with cyanuric acid , 1990 .

[30]  K. M. Ervin,et al.  Competitive Threshold Collision-Induced Dissociation: Gas-Phase Acidity and O−H Bond Dissociation Enthalpy of Phenol , 2004 .

[31]  G. Stark,et al.  Reactions of the Cyanate Present in Aqueous Urea with Amino Acids and Proteins , 1960 .

[32]  S. Mukherjee,et al.  Gas-phase acid-base properties of melamine and cyanuric acid , 2010, Journal of the American Society for Mass Spectrometry.

[33]  Dennys E. Angove,et al.  The Formation and Hydrolysis of Isocyanic Acid during the Reaction of NO, CO, and H2 Mixtures on Supported Platinum, Palladium, and Rhodium , 2001 .

[34]  Norbert Kalthoff,et al.  Measured and simulated vertical profiles of nitrous acid—Part I: Field measurements , 2003 .

[35]  Brett Taylor,et al.  Are emissions of black carbon from gasoline vehicles underestimated? Insights from near and on-road measurements. , 2012, Environmental science & technology.

[36]  Paul A. Makar,et al.  Cloud processing of gases and aerosols in a regional air quality model (AURAMS) , 2006 .

[37]  K. Kawamura,et al.  Motor exhaust emissions as a primary source for dicarboxylic acids in Los Angeles ambient air , 1987 .

[38]  S. Moebus,et al.  Traffic exposure and subclinical cardiovascular disease: is the association modified by socioeconomic characteristics of individuals and neighbourhoods? Results from a multilevel study in an urban region , 2009, Occupational and Environmental Medicine.

[39]  James N. Pitts,et al.  Photooxidation of aliphatic amines under simulated atmospheric conditions: formation of nitrosamines, nitramines, amides, and photochemical oxidant , 1978 .

[40]  F. Fehsenfeld,et al.  Calibration and evaluation of nitric acid and ammonia permeation tubes by UV optical absorption. , 2003, Environmental science & technology.

[41]  K. Kawamura,et al.  Determination of organic acids (C1-C10) in the atmosphere, motor exhausts, and engine oils. , 1985, Environmental science & technology.

[42]  L. E. Trimble,et al.  Conversion of NO to isocyanic acid and ammonium cyanate over Pd, Ir, and Pt-10% Rh catalysts , 1978 .

[43]  Elizabeth Pattey,et al.  Characterizing a Quantum Cascade Tunable Infrared Laser Differential Absorption Spectrometer (QC-TILDAS) for measurements of atmospheric ammonia , 2009 .

[44]  Efthimios Zervas.  Formation of organic acids from propane, isooctane and toluene/isooctane flames , 2005 .

[45]  A. Mellouki,et al.  Aspects of the atmospheric chemistry of amides. , 2010, Chemphyschem : a European journal of chemical physics and physical chemistry.

[46]  M. Jerrett,et al.  A Cohort Study of Traffic-Related Air Pollution and Mortality in Toronto, Ontario, Canada , 2009, Environmental health perspectives.

[47]  J. Marshall,et al.  Intake fraction of primary pollutants: Motor vehicle emissions in the South Coast Air Basin , 2003 .