:: Section 4
Urban Aerosol
Tabulated Summary
Table 2 summarizes the three modes of urban aerosols and their corresponding characterizations.
TABLE 2. Modes of Urban Aerosol
Modes of urban aerosol |
Sources |
Characterization |
| Nuclei Mode |
Combustion particles; gas-to-particle conversion |
0.001-0.1 μm; high concentration; rapid coagulation; short lifetime |
| Accumulation Mode |
Combustion particles; smog particles; coagulated nuclei-mode particles |
0.1-2.5 μm; slow coagulation; long lifetime; accounting for most of visibility effects |
| Coarse Particle Mode |
Windblown dusts; salt particles from sea spray; volcano eruptions; anthropogenic particles from agriculture and surface mining |
2.5-100 μm; readily settle down on surface; short lifetime |
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Which mode of aerosol has the longest lifetime in the atmosphere? Why? |
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