TY - JOUR

T1 - Effective Density and Mixing State of Aerosol Particles in a Near-Traffic Urban Environment

AU - Rissler, Jenny

AU - Nordin, Erik Z

AU - Eriksson, Axel C

AU - Nilsson, Patrik T

AU - Frosch, Mia

AU - Sporre, Moa K

AU - Wierzbicka, Aneta

AU - Svenningsson, Birgitta

AU - Löndahl, Jakob

AU - Messing, Maria E

AU - Sjogren, Staffan

AU - Hemmingsen, Jette G

AU - Loft, Steffen

AU - Pagels, Joakim H

AU - Swietlicki, Erik

PY - 2014/6/3

Y1 - 2014/6/3

N2 - 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%.

AB - 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%.

KW - Aerosols

KW - Cities

KW - Denmark

KW - Environmental Monitoring

KW - Particle Size

KW - Particulate Matter

KW - Time Factors

KW - Vehicle Emissions

U2 - 10.1021/es5000353

DO - 10.1021/es5000353

M3 - Journal article

C2 - 24798545

VL - 48

SP - 6300

EP - 6308

JO - Environmental Science & Technology

JF - Environmental Science & Technology

SN - 0013-936X

IS - 11

ER -