title: Ultrafine-Particle Emission Factors as a Function of Vehicle Mode of Operation for LDVs Based on Near-Roadway Monitoring.
abstract: This paper presents ultrafine-particle (UFP) emission factors (EFs) as a function of vehicle mode of operation (free flow and congestion) using (1) concurrent 5 min measurements of UFPs and carbon monoxide (CO) concentration, wind speed and direction, traffic volume and speed near a roadway that is restricted to light-duty vehicles (LDVs) and (2) inverse dispersion model calculations. Short-term measurements are required to characterize the highly variable and rapidly changing UFP concentration generated by vehicles. Under congestion conditions, the UFP vehicle EFs increased from 0.5 × 10(13) to 2 × 10(13) (particles km(-1) vehicle(-1)) when vehicle flow increased from 5500 to 7500 vehicles/h. For free-flow conditions, the EF is constant at 1.5 × 10(13) (particles km(-1) vehicle(-1)). The analysis is based on the assumption that air-quality models adequately describe the dilution process due to both traffic and atmospheric turbulence. The approach used to verify this assumption was to use an emission factor model to determine EFs for CO and then estimate dilution factors using measured CO concentrations. This procedure eliminates the need to rely only on air quality models to generate dilution factors. The EFs are suitable for fleet emissions under real-world traffic conditions.
authors.affiliation: Department of Civil, Architectural, and Environmental Engineering, Illinois Institute of Technology , Chicago, Illinois 60616, United States.
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Zhai
authors.affiliation: Department of Civil, Architectural, and Environmental Engineering, Illinois Institute of Technology , Chicago, Illinois 60616, United States.
authors.forename: Dongqi
authors.initials: D
authors.lastname: Wen
authors.affiliation: Department of Civil, Architectural, and Environmental Engineering, Illinois Institute of Technology , Chicago, Illinois 60616, United States.
authors.forename: Sheng
authors.initials: S
authors.lastname: Xiang
authors.affiliation: Department of Civil, Architectural, and Environmental Engineering, Illinois Institute of Technology , Chicago, Illinois 60616, United States.
authors.forename: Zhice
authors.initials: Z
authors.lastname: Hu
authors.affiliation: Department of Civil, Architectural, and Environmental Engineering, Illinois Institute of Technology , Chicago, Illinois 60616, United States.
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Noll
mesh_terms: D002248:Carbon Monoxide / Q000032:analysis; D004784:Environmental Monitoring; D008962:Models, Theoretical; D052638:Particulate Matter / Q000032:analysis*; D001335:Vehicle Emissions / Q000032:analysis*; D014919:Wind
chemical_list: D052638:Particulate Matter; D001335:Vehicle Emissions; D002248:Carbon Monoxide