title: Measurements of gas phase acids in diesel exhaust: a relevant source of HNCO?
abstract: 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.
authors.affiliation: Air Quality Processes Research Section, Environment Canada , 4905 Dufferin Street, Toronto, Ontario, Canada M3H 5T4.
authors.forename: Jeremy J B
authors.initials: JJ
authors.lastname: Wentzell
authors.forename: John
authors.initials: J
authors.lastname: Liggio
authors.forename: Shao-Meng
authors.initials: SM
authors.lastname: Li
authors.forename: A
authors.initials: A
authors.lastname: Vlasenko
authors.forename: Ralf
authors.initials: R
authors.lastname: Staebler
authors.forename: Gang
authors.initials: G
authors.lastname: Lu
authors.forename: Marie-Josée
authors.initials: MJ
authors.lastname: Poitras
authors.forename: Tak
authors.initials: T
authors.lastname: Chan
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Brook
mesh_terms: D003485:Cyanates / Q000737:chemistry*; D005740:Gases / Q000737:chemistry*; D001335:Vehicle Emissions
chemical_list: D003485:Cyanates; D005740:Gases; D001335:Vehicle Emissions; C005057:isocyanic acid