2.Calculate the mass (in mg) of fine particles inhaled by an adult each year, as

Question

2.Calculate the mass (in mg) of fine particles inhaled by an adult each year, assuming that he/she inhales about 335.8 L of air per hour and that the average concentration of PM2.5 (fine particulate matter with particle sizes of less than 2.5 m) is 4.658 g m-3.

3.Assuming that the average size (=diameter) of these particles is 269.6 nm, their shape is spherical, and their density is 0.907 g/mL, calculate the total surface area (in m2) of the particulate matter inhaled by the adult in Problem 2. Hint: the area of a sphere is 4r2 and its volume is (4/3)r3, where r is the radius. Thanks for your help

Explanation / Answer

Volume of Air inhaled per hour = 335.8 L

Therefore,

Volume of Air Inhaled per year = 335.8 x 24 x 365 = 2941608 L = 2941.608 m^3

Also it is given that average conc. of PM2.5 = 4.658 g/m^3

Therefore,

PM2.5 in 2941.608 m^3 of air = 2941.608 x 4.658 = 13702.01 g = 13.7 mg

Mass (in mg) of fine particles inhaled by an adult each year = 13.7 mg

3)

Volume of Particles = Mass / Density = 13.7 x 10^-3 / 0.907 = 0.0151 mL = 0.0151 cm^3 = 1.51 x 10^-8 m^3

Volume = (4/3) x pi x r^3 = 1.51 x 10^-8

=> r = 1.534 x 10^-3 m

Surface Area = 4 x pi x r^2 = 4 x 3.14 x (1.534 x 10^-3)^2 = 2.95 x 10^-5 m^2

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