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Atmospheric Aerosol


:: Section 4

Urban Aerosol

  Section Contents

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
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


Which mode of aerosol has the longest lifetime in the atmosphere? Why?