Atmospheric Aerosol

:: Section 4

Urban Aerosol

The urban aerosol is dominated by anthropogenic sources. Aerosol mass concentrations in urban areas range from a few tens of μg/m³ to 1 mg/m³ during air pollution episodes in heavily polluted cities in developing countries. Below are photos taken in Guangzhou, China and Mumbai, India, during the air pollution episodes. From the photos you can see that the hazes produced by the urban aerosol greatly impaired the visibility. (For more information on visibility, see Section 9 ).

Guangzhou, China	Mumbai, India

Aerosols are categorized by size into modes. The most common way to present particle size distribution data for the urban aerosol is in terms of the three modes: the nuclei, accumulation, and coarse particle modes. Details in each mode are provided in the following pages.

The average urban aerosol size distributions are shown in the following figure. Most of the particles are in the nuclei mode by count, but most of their mass is split between the accumulation and coarse particle modes.

How many 0.01 μm particles are necessary to have the same mass as one 1 μm particle?