title: Effective density and mixing state of aerosol particles in a near-traffic urban environment.
abstract: In urban environments, airborne particles are continuously emitted, followed by atmospheric aging. Also, particles emitted elsewhere, transported by winds, contribute to the urban aerosol. We studied the effective density (mass-mobility relationship) and mixing state with respect to the density of particles in central Copenhagen, in wintertime. The results are related to particle origin, morphology, and aging. Using a differential mobility analyzer-aerosol particle mass analyzer (DMA-APM), we determined that particles in the diameter range of 50-400 nm were of two groups: porous soot aggregates and more dense particles. Both groups were present at each size in varying proportions. Two types of temporal variability in the relative number fraction of the two groups were found: soot correlated with intense traffic in a diel pattern and dense particles increased during episodes with long-range transport from polluted continental areas. The effective density of each group was relatively stable over time, especially of the soot aggregates, which had effective densities similar to those observed in laboratory studies of fresh diesel exhaust emissions. When heated to 300 °C, the soot aggregate volatile mass fraction was ∼10%. For the dense particles, the volatile mass fraction varied from ∼80% to nearly 100%.
authors.affiliation: Ergonomics and Aerosol Technology, ‡Division of Nuclear Physics, and §Solid State Physics, Lund University , P.O. Box 118, SE-221 00, Lund, Sweden.
authors.forename: Jenny
authors.initials: J
authors.lastname: Rissler
authors.forename: Erik Z
authors.initials: EZ
authors.lastname: Nordin
authors.forename: Axel C
authors.initials: AC
authors.lastname: Eriksson
authors.forename: Patrik T
authors.initials: PT
authors.lastname: Nilsson
authors.forename: Mia
authors.initials: M
authors.lastname: Frosch
authors.forename: Moa K
authors.initials: MK
authors.lastname: Sporre
authors.forename: Aneta
authors.initials: A
authors.lastname: Wierzbicka
authors.forename: Birgitta
authors.initials: B
authors.lastname: Svenningsson
authors.forename: Jakob
authors.initials: J
authors.lastname: Löndahl
authors.forename: Maria E
authors.initials: ME
authors.lastname: Messing
authors.forename: Staffan
authors.initials: S
authors.lastname: Sjogren
authors.forename: Jette G
authors.initials: JG
authors.lastname: Hemmingsen
authors.forename: Steffen
authors.initials: S
authors.lastname: Loft
authors.forename: Joakim H
authors.initials: JH
authors.lastname: Pagels
authors.forename: Erik
authors.initials: E
authors.lastname: Swietlicki
mesh_terms: D000336:Aerosols / Q000032:analysis / Q000737:chemistry*; D002947:Cities; D003718:Denmark; D004784:Environmental Monitoring / Q000379:methods; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis / Q000737:chemistry*; D013997:Time Factors; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D000336:Aerosols; D052638:Particulate Matter; D001335:Vehicle Emissions