APES Unit 7 review

Air pollution

The introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm  plants, animals, and materials such as buildings, or to alter ecosystems.

Primary pollutants

Comes directly out of a smokestack, exhaust pipe, or natural source. 

* Carbon monoxide (CO)
* Carbon dioxide (CO2) 
* Sulfur dioxide (SO2) 
* Nitrogen oxides (NOx) 
* Particulate matter (PM)

Secondary pollutants

A primary pollutant that has undergone transformation in the presence of sunlight, water, oxygen, or other compounds. 

* Ozone (O3) 
* Sulfuric acid (H2SO4)
* Nitric acid (N2O)

**NOSCLP**

1. **N**itrogen oxides (NOx)


1. **O**zone (Ground-level, tropospheric; not stratospheric)
2. **S**ulfur oxide (SO2)
3. **C**arbon oxide (CO)
4. **L**ead (and other toxic metals)
5. **P**articulate matter 

**Nitrogen oxides (NOx)**

* Primary sources: mobile automobiles and stationary fossil fuel combustion
* An ozone precursor - leads to formation of photochemical smog 
* Respiratory irritant - increases susceptibility              to respiratory infection

**Ozone**

a highly reactive gas that is a major component of photochemical smog

* Causes and aggravates respiratory illness
* Damages plants, rubber tires, fabrics, paints

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Ozone in stratosphere is good

Ozone in troposphere is **bad**

**Sulfur dioxide (SO2)**

* A corrosive gas that comes from combustion of coal and oil. (S + O2 → SO2)
* Released in large quantities during volcanic eruptions and in forest fires.

SO2 can be converted into sulfuric acid (H2SO4) that returns to earth as acid rain.

**Carbon Oxides**

* Carbon monoxide (CO) - common                                              emission in vehicle exhaust and other combustion processes;  can be a significant component of air pollution in urban areas
* Carbon dioxide (CO2) - released by burning fossil fuels; appears to be steadily increasing each year

**Lead**

* A gasoline additive
* Also found in oil, coal, old paint
* It is a neurotoxin - impairs central nervous system  At low concentrations, can have measurable effects on learning and ability to concentrate
* Does not break down in the environment

**Particulate Matter (PM)**

* Solid particles and liquid droplets small and light enough to remain suspended in air
* PM causes 60,000 deaths per year in the U.S.
* Fine: PM10 (< 10 µm)
* Ultrafine: PM2.5 (< 2.5 µm)

Sulfurous Smog (SO2)

* Smog dominated by sulfur dioxide and sulfate compounds
* Emitted by burning oil and coal 
* Also known as: Gray smog, Industrial smog, London smog

 Photochemical Smog

* Photochemical smog is formed when nitrogen oxides (NOx) and volatile organic hydrocarbons (VOCs) react with heat and sunlight to produce ozone (O3).
* Also known as:Los Angeles–type smog, Brown smog

Volatile Organic Compounds (VOCs)

* **Organic compounds that evaporate (sublimate) at typical atmospheric temperatures**
* Formed by evaporation of fuels, solvents, paints, and incomplete combustion of fuels such as gasoline
* A precursor to ozone formation

**Thermal inversion** 

A relatively warm layer  of air at mid-altitude covers a layer of cold, dense air below

**Inversion layer** 

Layer of warm air that traps emissions in a thermal inversion

Outdoor air pollution can increase by:

* Urban buildings (slow wind dispersal of pollutants)
* High tempertures (promote photochemical reactions)
* Mountains (promote thermal inversions)

Four Indoor Air Pollutants

1. Carbon monoxide (CO)
2. Asbestos
3.   Radon


4. VOCs

Carbon monoxide (CO)

* Is an asphyxiant
* From burning wood for cooking and heating
* From tobacco smoke

Asbestos

* Long thin, fibrous, silicate particulates
* Formerly used as insulation in buildings
* Can cause cancer when inhaled

  Radon

* A naturally occurring radioactive gas produced by the decay of uranium found in rocks and soils.
* Seeps into homes through cracks in the foundation, groundwater, or rocks.

VOCs

* Volatile organic compounds used in furniture, paint, and building materials
* Ex: Formaldehyde (particle board, glue)

Sick Building Syndrome

Sick Building Syndrome (SBS) affects large office buildings where workers breathe in pollutant gases, which are released from the materials and equipment in the office

Acid deposition

nitrogen oxides and sulfur oxides are released into the air and combine with oxygen and water.

Acid rain

* Acid rain is rain water having pH less than 5.6.
* Acid rain can have harmful effects on plants, animals and humans.

**Coal Gasification (input)**

* The process of producing syngas – a mixture consisting CO, H2, CO2, CH4, and H2O from coal, water, air and/or O2.
* Clean-burning coal with little to no carbon emissions
* A part of “clean coal” technology

**Fluidized-bed Combustion (input)**

* Can burn any type of fuel at high efficiency.
* Steam is pumped into a boiler to burn a mixture of powdered coal and crushed limestone (neutralizes sulfur emissions).

**Regulations (input)**

* Laws like the Clean Air Act (but many airports are exempt)
* Economic solutions cap-and-trade A.K.A., “Pay-to-Pollute” policies

**Vapor Recovery Nozzle (output)**

A vapor recovery nozzle is an air pollution control device on a gasoline pump that prevents fumes from escaping into the atmosphere when fueling a motor vehicle.

**Catalytic converter (output)**

A catalytic converter is an air pollution control device for engines that converts pollutants (CO, NOx, and hydrocarbons) in exhaust into less harmful molecules (CO2, N2, O2, and H2O).

**Wet Scrubber (output)**

Particles are “scrubbed” from the exhaust stream by water droplets. A water-particle “sludge” is collected and processed for disposal.

**Electrostatic Precipitator (output)**

* Can remove 99% of particulate matter
* Does not remove hazardous ultrafine particles
* Produces toxic dust that must be safely disposed of
* Uses large amounts of electricty