Session 7 Particle Size Distributions Fall 2008 By

Session 7 Particle Size Distributions Fall 2008 By Wen-Whai Li Particle Size Distributions 1

Determining the Terminal Velocity Fall 2008 By Wen-Whai Li Particle Size Distributions 2

Determining the Terminal Velocity Fall 2008 By Wen-Whai Li Particle Size Distributions 3

Particle Size Distributions Characteristics: • Wide range in size: 5 orders of magnitude 1 nm – 100 µm • Wide range in shape: particles come in all shapes • Wide range in numbers: 104 -6 in nanometers and 100 -2 in micrometers • Variable density and aerodynamic properties • Any of the properties, such as number, mass, size, surface area, etc, may have various adverse health effects Fall 2008 By Wen-Whai Li Particle Size Distributions 4

Particle Size Distributions Fall 2008 By Wen-Whai Li Particle Size Distributions 5

Particle Size Distributions Fall 2008 By Wen-Whai Li Particle Size Distributions 6

Particle Size Distributions Fall 2008 By Wen-Whai Li Particle Size Distributions 7

Particle Size Distributions Fall 2008 By Wen-Whai Li Particle Size Distributions 8

Particle Size Distributions Fall 2008 By Wen-Whai Li Particle Size Distributions 9

Mode, Median, and Mean of Aerosol Size • Mode: the diameter of the most frequent size • Median: The diameter for which ½ of the total number of particles are smaller and ½ are larger • Arithmetic Mean: The sum of all particle sizes divided by the total number of particles In general, Mode < Median < Mean • Geometric Mean: the logarithm of the arithmetic mean of the logarithmic of all values or the nth root of product of the N values Fall 2008 By Wen-Whai Li Particle Size Distributions 10

Mode, Median, and Mean of Aerosol Size Geometric Mean: Fall 2008 By Wen-Whai Li Particle Size Distributions 11

Moment Averages Fall 2008 By Wen-Whai Li Particle Size Distributions 12

Lognormal Distribution Fall 2008 By Wen-Whai Li Particle Size Distributions 13

Lognormal Distribution Fall 2008 By Wen-Whai Li Particle Size Distributions 14