Chapter 13 Notes

List three sources and types of natural air pollutants.

1, natural fires - smoke; 2, volcanoes - ash and acid; 3, sea spray - sulfur.

What are the typical units of measurement of gaseous and particulate air pollutants? Do they all vary with air temperature and pressure?

Mass of pollutant per unit volume of air mixture or volume of pollutant per million volumes of the air plus pollutant mixture. The relationship between ppm and mg/m³ depends on temperature and pressure.

Discuss five strategies for air pollution control.

1, prevent pollution from initially occurring; 2, source location to minimize adverse impacts; 3, fuel substitutions or process changes to reduce the settling of harmful airborne pollutants; 4, using natural gas as a cleaner burning fuel; 5, correct operation and maintenance practices to ensure the release of some pollutants is not a result of human error.

What is meant by atmospheric stability? How does it affect air quality?

A rate by which air temperature drops characterized by an increase in actual air temperature with increasing altitude is called temperature inversion, and results in an extremely stable atmosphere. They prevent the upward mixing and dispersion of contaminants, causing major air pollution episodes.

Describe the key devices used to control gaseous air pollution. What is an FGD system used for?

Absorption, transfers gaseous pollutant into a contacting liquid; flue gas desulfurization, gas adsorption in a scrubber of oxides of sulfur; adsorption, gas molecules are attracted to and held to the surface of a solid; incineration, convert VOCs into carbon dioxide.

Briefly explain the difference between the anthropogenic greenhouse effect and the natural greenhouse effect. Why is the term "greenhouse effect" not completely accurate as a synonym for global warming?

Anthropogenic greenhouse effect is the direct result of the accumulation of trace gases in the air from human activities, while natural greenhouse effect is a normal result of the presence of a blanket of air around Earth. The temperatures inside a real greenhouse rise much higher than is possible by the effect of Earth's atmosphere alone.

Briefly discuss typical types and sources of hazardous air pollutants.

Asbestos, from demolition or renovation of structures with asbestos fireproofing; benzene, mostly from gasoline-powered vehicles; beryllium, from foundries, ceramic factories, incinerators, and others; mercury, found in coal, released when coal is burned; vinyl chloride, emitted by plastics processing facilities; and radionuclides, or radioactive air pollutants.

Discuss the major techniques (i.e., absorption and adsorption) and the devices used to sample and measure gaseous air pollutants.

Bubbler is a typical absorption sampler, colorimetric tubes add chemicals to the adsorbent to form an identifying color.

Identify and briefly discuss the major greenhouse gases.

Carbon dioxide, emitted mostly from fossil fuel combustion, absorbs most of the heat trapped by the atmosphere; chlorofluorocarbons (CFCs), are 1,000 times stronger than carbon dioxide as a greenhouse gas, cause stratospheric zone depletion; methane and nitrous oxide, which are natural but increasing from humans, have long lives with long lasting effects.

List the major sources and effects of indoor air pollution.

Combustion products, such as environmental tobacco smoke; radon, inhaled radon can release radiation that can damage lung tissue; asbestos, can accumulate in lungs if inhaled, lead to many adverse health effects; organics from household products, some of which are highly toxic or carcinogenic; formaldehyde, eye and throat irritation, nausea, and respiratory distress; lead, at high levels can cause convulsions, coma, even death, delays in physical and mental development of exposed children; and biological contaminants, transmission of infectious diseases through the air.

What is the difference between criteria air pollutants and hazardous air pollutants?

Criteria pollutants tend to harm human health, diminish environmental quality, and damage property. Hazardous air pollutants are considered to be immediately harmful to human health and are mostly associated with certain specific sources.

What is the difference between dust and fume? Between mist and spray? Is fly ash synonymous with smoke?

Dust particles (1 to 100 µm) are slightly larger than fume particles (less than 1 µm). A mist is classified between 0.1 µm and 10 µm, while a spray is greater than 10 µm. Fly ash is not smoke; the particles making up fly ash are larger than those of smoke.

Discuss the major techniques and devices used to sample and measure particulate air pollutants.

Dust-fall bucket, open bucket is positioned to trap particles. High-volume samplers use a filtration technique rather than gravity.

Describe methods for controlling and reducing indoor air pollution for each of the major sources.

Exhaust fans help reduce combustion products, sealing house walls exposed to earth reduces radon circulation, asbestos is best left in a state where its not in the air, dehumidifiers and air conditioning help reduce formaldehyde, and controlling humidity levels can eliminate the threat of biological contaminants.

What are the major gaseous constituents of fresh (clean) air?

Oxygen, nitrogen, argon, and carbon dioxide.

What size range of particulates is of most significance with respect to human health? What size range of particulates will readily settle out of the air?

Particles 10 µm in size or smaller are of most concern with regard to adverse effects on human health, especially fine particles 2.5 µm or smaller. These fibers can penetrate deep into the lungs when inhaled. Airborne particles 10 µm or larger readily settle out of the air.

What is the difference between primary air pollutants and secondary air pollutants?

Primary pollutants are emitted directly into the air from a specific source, while secondary pollutants are formed in the atmosphere by complex chemical reactions between primary pollutants and sunlight.

Give a brief definition of air pollution. What is meant by the term anthropogenic air pollution?

The presence of certain substances in the air in high enough concentrations and for long enough durations to cause undesirable effects. Anthropogenic means it is caused by human activity.

Briefly discuss sick building syndrome.

When the occupants of a building have symptoms that do not fit the pattern of any particular illness and are difficult to trace to a specific source. Applies when more than 20% of occupants complain of health problems for 2 weeks or more.