Question

Problem 6. Studies have shown that a white surface becomes noticeably dusty when 0.2 percent of its area is covered by black particles (i.e., soot). Assume that the same relationship applies for soil dust particles. Estimate the time required for an initially clean, horizontal surface to appear dusty if it is exposed to an atmosphere containing 10 μg m-3 of soil-dust particles of diameter 5 μm. Assume that the particles are spherical and have a density of 2.5 g cm3 and particles do not overlap each other after settled onto the surface. Hair 1.98x105 kg/m-s. (Hint, the setting/deposition flux equals the setting velocity multiples particle number concentration)

Answer 1