Variability of Apparent Particle Density of an Urban Aerosol
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- 作者：Mike Pitz ; Josef Cyrys ; Erwin Karg ; Alfred Wiedensohler ; H.-Erich Wichmann ; and Joachim Heinrich
- 刊名：Environmental Science & Technology
- 出版年：2003
- 出版时间：October 1, 2003
- 年：2003
- 卷：37
- 期：19
- 页码：4336 - 4342
- 全文大小：149K
- 年卷期：v.37,no.19(October 1, 2003)
- ISSN：1520-5851
文摘
The day to day and diurnal variation of apparent particledensity was studied using highly time-resolved measurementsof particle number distribution and fine-particle massconcentration. The study was conducted in Erfurt, Germany,from January 1, 1999, to November 22, 2000. A setupconsisting of a differential mobility particle spectrometerand a laser aerosol spectrometer was used for particle numberdistribution measurements. PM2.5 particle mass wasmeasured in parallel on an hourly basis using a taperedelement oscillating microbalance (TEOM) and on daily baseby using a Harvard marple impactor (HI). For the estimationof the mean apparent density of particles, number sizedistributions were converted into volume size distributions,assuming that the particles were spherically shaped.The volume size distributions were integrated over therange of 10 nm to 2.03 
m Stokes equivalent diameter toobtain volume concentrations. Mean apparent particle densitywas calculated as ratio of mass concentration andvolume concentration. The mean apparent particle density,determined from HI and number size distribution on adaily basis was 1.6 ± 0.5 g cm-3. We found a strong day-to-day variation of apparent density ranging from 1.0 to2.5 g cm-3 (5th and 95th percentile). Furthermore, the apparentdensity showed pronounced diurnal pattern both insummer and in winter and also on weekdays and weekends.The apparent density was lowest in the morning andhighest in the afternoon. The mean apparent density onan hourly basis was 1.4 ± 0.5 and 1.5 ± 0.5 g cm-3 forPM2.5TEOM and corrected PM2.5TEOM using regression equationbetween daily mass concentration of HI and TEOM,respectively. The strong diurnal variation of apparentparticle density was associated predominantly with thevertical temperature inversion and with traffic intensity.Thus, the apparent particle density depends on the physicalparticle properties and might be related to chemicalcomposition of the sampled particle.
m Stokes equivalent diameter toobtain volume concentrations. Mean apparent particle densitywas calculated as ratio of mass concentration andvolume concentration. The mean apparent particle density,determined from HI and number size distribution on adaily basis was 1.6 ± 0.5 g cm-3. We found a strong day-to-day variation of apparent density ranging from 1.0 to2.5 g cm-3 (5th and 95th percentile). Furthermore, the apparentdensity showed pronounced diurnal pattern both insummer and in winter and also on weekdays and weekends.The apparent density was lowest in the morning andhighest in the afternoon. The mean apparent density onan hourly basis was 1.4 ± 0.5 and 1.5 ± 0.5 g cm-3 forPM2.5TEOM and corrected PM2.5TEOM using regression equationbetween daily mass concentration of HI and TEOM,respectively. The strong diurnal variation of apparentparticle density was associated predominantly with thevertical temperature inversion and with traffic intensity.Thus, the apparent particle density depends on the physicalparticle properties and might be related to chemicalcomposition of the sampled particle.