Air Pollution and Control - Examples & Applications

Solved Problems

Applying Gaussian Plume and Box Models

Problem 1: Unit Conversion: ppm to

\mu g/m^3

Convert a concentration of 5 ppm of Sulfur Dioxide ( $SO_2$ ) to $\mu g/m^3$ at standard temperature and pressure (STP: 25°C, 1 atm).

Given:

Checklist

Molecular Weight of $S = 32$
Molecular Weight of $O = 16$
Temperature ( $T$ ) = $298 \text{ K}$ ( $25 + 273$ )
Pressure ( $P$ ) = $1 \text{ atm}$
Universal Gas Constant ( $R$ ) = $0.08205 \text{ L atm} / (\text{mol K})$

Example

Unit Conversion: ppm to μg/m³

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Problem 2: Box Model Calculation

Consider a city as a "box" with dimensions $W \times L \times H$ . Clean air enters with wind speed $u$ , and polluted air leaves. Pollutants are emitted inside the box at rate $Q$ . Assume complete instantaneous mixing throughout the volume.

Calculate the steady-state concentration ( $C$ ) given:

Checklist

Emission Rate ( $Q$ ) = $500 \text{ g/s}$
Wind Speed ( $u$ ) = $4 \text{ m/s}$
City Width ( $W$ ) = $2,000 \text{ m}$ (perpendicular to wind)
Mixing Height ( $H$ ) = $1,000 \text{ m}$
Length ( $L$ ) along wind direction = $5,000 \text{ m}$
Initial background concentration ( $C_{in}$ ) = $0$

Example

Box Model Calculation

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Atmospheric Dispersion (Gaussian Plume)

Estimating downwind ground-level concentration

A smokestack emits sulfur dioxide ( $SO_2$ ) at a rate of $100 \text{ g/s}$ . The effective stack height ( $H$ ) is $50 \text{ m}$ . The average wind speed ( $u$ ) is $5 \text{ m/s}$ . At a specific downwind distance, the dispersion coefficients are $\sigma_y = 100 \text{ m}$ and $\sigma_z = 50 \text{ m}$ . Estimate the ground-level concentration ( $z=0$ ) directly along the plume centerline ( $y=0$ ).

Example

Ground-Level Concentration Calculation

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Case Study: Photochemical Smog in Los Angeles

Conditions leading to severe air pollution episodes

Los Angeles is historically famous for intense photochemical smog. Analyze the geographic and meteorological conditions that contribute to this phenomenon, and explain the chemical process involved.

Example

Smog Formation Analysis

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