Introduction
Author
Isabelle Jacobson
PHYS F212X F02, Spring 2019
Professor David Newman
University of Alaska Fairbanks

Air Pollution

Visual air pollution
 12
What is air pollution? As defined by the Environmental Protection Agency, air pollution is made of specific pollutants that can harm someone's health, hurt the environment, and cause property damage. The Clean Air Act was put in place to require the EPA to set particular standards (National Ambient Air Quality Standards) for six criteria air pollutants that are most commonly observed. These pollutants are ground-level ozone, particulate matter, carbon monoxide, lead, sulfur dioxide, and nitrogen dioxide.13 The pollutant that is the focus of this website is particulate matter, which is posing health risks to the community of Fairbanks, Alaska.
Particulate matter is able to remain suspended and move through the atmosphere by wind direction, wind intensity, difference in indoor and outdoor air density, difference in indoor and outdoor air temperatures, and more. In buildings, flow is induced by buoyancy, which then influences the path traveled by the particles.17

Particles in the air indoors stick to surfaces they come in contact with. There is a "concentration gradient" of particles near the surface. This creates constant diffusion of particles to the surface. For this, Fick's first law of diffusion is applied:
E1
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J (deposition rate) is the number of particles per unit surface area per unit time
n-initial is the initial concentration of particles, D is the particle diffusion coefficient.17

Another way to look at the deposition rate can be by looking at deposition velocity:
E2
17

The deposition loss rate coefficient may be calculated by looking at deposition velocity on different surfance orientations and surface areas:
E3
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Beta is the deposition loss rate coefficient
A(w), A(h), A(d) are total areas for vertical wall, upward-facing, downward-facing horizontal surfaces
V(dw), V(du),V(dd) are deposition velocities for vertical wall, upward-facing, downward-facing horizontal surfaces
V is the volume of enclosure17

VTS is the terminal settling velocity (for particle settling from gravitational force, result of "balance drag and gravity"):E4E5
17
eta is air viscosity
rho(p) and rho(g) are density of particle and density of air
d(p) is particle diameter
g is acceleration due to gravity
C(d) is drag coefficient17

These particles are deposited indoors due to these. Once particles are deposited, they may remain there before being suspended again, and this may keep happening. Particulate molecules indoors are observed to be in higher concentration than outdoors.17 As these particles cycle through the air and surfaces indoors, there is a higher chance of inhalation and negatively impacting health.