Chicago winter aerosol size spectra.

Abstract

H The atmospheric aerosol in Chicago was characterized with respect to particle size distribution and number concentration by means of 68 samples taken during weekday daylight hours in winter, 1974. The size range 0.01-4.0 pm was covered by two instruments: an electric mobility particle size analyzer and an optical counter. The geometric mean number concentration in the 0.01-4.0-pm diameter range was 303 000 cc-l. Wind speed and direction were the main meteorological factors causing changes in the aerosol concentration. For most particle sizes the concentration decreased with increasing wind speed, but the two smallest size classes (-0.01 and -0.02 wm) were relatively unaffected. Wind directions in the sector 5-65' resulted in average aerosol concentrations one-third to onehalf of those for winds in all other sectors. This was tentatively attributed to low background aerosol concentration for winds in that sector.Data are presented on the size distribution and number concentration of the winter atmospheric aerosol in Chicago. The data were taken during weekday daylight hours at IIT Research Institute on Chicago's near south side. Two instruments were used that together cover the size range 0.01-4.0 pm. The data presented consist of the average particle number concentrations as a function of particle size and of correlations to several meteorological variables.The Chicago atmospheric aerosol data reported here compliment the data available from the City of Chicago's Department of Environmental Control ( I ) and from literature sources (2-5). Sampling SiteAll atmospheric aerosol samples were taken at IIT Research Institute at 35th and State Streets on Chicago's near south side. Figure 1 shows the area. The major potential aerosol sources near IITRI are: the Dan Ryan Expressway and the Rock Island Commuter Train (both pass within 240 m of IITRI); moderate and heavy industry located beyond 5 km to the west and beyond 10 km to the south; a multiplicity of space heating units in the residential and commercial area within 5 km. Lake Michigan (2 km east) was expected to be relatively free of sources.Two sampling locations were used a t IITRI. The first 45 samples (1/1/74-2/18/74) were taken through a north-facing third floor window in the northwest corner of the Chemistry Research Building. Since this location was potentially affected by numerous local sources (roof-top hood exhausts, street level dust, a small incinerator), 23 samples (2/20/74-3/7/74) were drawn for comparison from an east-facing 20th floor window in the Research Tower. The elevation above State Street was 64 m. Apparatus and ProcedureThe apparatus used in this work is shown schematically in Figure 2. The two main sampling instruments were a singleparticle optical counter and an electric mobility particle size analyzer.The electric mobility particle size analyzer used in this work was designed and constructed at IIT Research Institute (6). This instrument was used to obtain aerosol number concentrations in 13 size classes from 0.0096 to 0.092 pm diamete...

Atmospheric effects in astroparticle physics experiments and the challenge of ever greater precision in measurements

“…Another kind of instruments more sophisticated permits to solve these issues, especially giving valuable information about the shape and/or refractive index of atmospheric particles: the multi-angle aerosol spectrometer probe (MASP) [165], measuring light scattered by individual particles for polar angles of 30 • − 60 • and 120 • − 150 • . Other techniques based on the aerodynamic particle size [166] (sizes greater than 0.2 − 0.5 µm), particle electrical mobility [167][168][169] (3 − 900 nm), particle diffusivity [170,171] (particles smaller than 0.1 µm) or particle growth by condensation [172] (3 − 10 nm) are also available to estimate aerosol size distribution.…”

On-line Analysis of Urban Particulate Matter Focusing on Elevated Wintertime Aerosol Concentrations

“…This is believed to be a result of less oxidants in the winter, that would reduce hetero- and homogeneous SO 2 oxidation. Other changes in general meteorological patterns during the winter such as a lower mixing height for the atmospheric boundary layer, changes in wind speeds/directions, and the presence of temperature inversions may also contribute to PM changes ( − ).…”