Environmental Engineering - Air Pollution Notes

Understand the nature of industrial air pollutants and their impacts on the environment.
Assess air quality and quality standards.
Identify potential air pollutants and control/treatment techniques.

Air pollution occurs when undesirable solid or gaseous particles are present in the air in quantities that are harmful to human health and the environment.

Four main types of air pollution sources:
- Mobile sources: Cars, buses, planes, trucks, and trains.
- Stationary sources: Power plants, oil refineries, industrial facilities, and factories.
- Area sources: Agricultural areas, cities, and wood-burning fireplaces.
- Natural sources: Wind-blown dust, wildfires, and volcanoes.

Air pollutants are classified into primary and secondary pollutants.
Primary pollutants: Directly emitted from their source.
Secondary pollutants: Result from chemical reactions in the atmosphere between primary pollutants and other substances, including volatile organic compounds (VOCs).
Particulate matter (PM) is a key indicator of air pollution, including tiny particles from brake and tire wear.

Primary air pollutants
- Nitrogen dioxide ( $NO<em>2$ ): Forms when $N</em>2$ and $O_2$ react, typically in high-temperature combustion processes, such as automobile engines.
Secondary air pollutants
- Ground-level ozone ( $O_3$ ): Created through the reaction of NOx and volatile organic compounds (VOCs) under strong sunlight.
- Acid rain: Results from the reaction between $SO_2$ or nitrogen oxides (NOx) and water in the atmosphere, leading to acidic precipitation.

Health Effects: Air pollutants can cause respiratory irritation or diseases, elevate blood pressure, and lead to lung cancer or respiratory failure.
Environmental Effects:
- Greenhouse gases like carbon dioxide contribute to global warming.
- Chronic exposure of leaves to air pollutants can damage their waxy coating, leading to excessive water loss and making them more vulnerable to diseases, pests, drought, and frost.

The upper stratosphere contains a significant amount of ozone ( $O_3$ ), which acts as an effective screen for ultraviolet light.
In the absence of pollutants, the creation and breakdown of ozone are governed by natural forces.
Certain pollutants can accelerate the breakdown of ozone.

The Air Quality Index (AQI) is a measure used to communicate how clean or polluted the air is and the potential health effects associated with it.
It is typically represented on a scale that ranges from good to hazardous, with values and color codes indicating the level of pollution.