Environmental Science - Chapter 10

Volatile Organic Compounds (VOCs)

organic compounds that become vapors at typical atmospheric temperatures

What is the difference between a primary and secondary pollutant?

A primary pollutant is an air pollutant emitted directly from a source. A secondary pollutant is not directly emitted as such, but forms when other pollutants (primary pollutants) react in the atmosphere.

How does an inversion layer influence air pollution events?

An inversion layer is a warm layer that traps emissions that then accumulate beneath it. These trapped emission often cause a severe pollution event. Thermal inversions can also lead to other forms of pollution. For example, in the northern Chinese city of Tianjin, 1000 people suffered carbon monoxide poisoning or respiratory ailments from the polluted air. Eleven died.

chlorofluorocarbons (CFCs)

A family of organic compounds whose properties make them ideal for use in refrigeration and air-conditioning.

thermal inversion

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

What is acid deposition?

Acid deposition refers to deposition with a pH lower than 5.6. Acid deposition is largely the result of human activity. Although natural processes such as volcanoes may also contribute. Acid deposition is also called acid rain.

What are some approaches to smog reduction?

Control efforts must be directed toward reducing the precursors, or primary pollutants, that contribute to smog. To reduce smog though, with fewer VOCs in the are there are fewer compounds to interact with nitrogen oxides, and thus more nitrogen oxide will be available to recombine with ozone. Most recently, efforts have been to reduce nitrogen oxide emissions, which appears to be a more effective method of controlling smog.

What are the major effects of acid deposition?

Effects of acid deposition may be direct, such as lowering of the pH of lake water, or indirect. Lower pH can also lead to mobilization of metals an indirect effect. People are not harmed by direct contact with precipitation at the acidities commonly experienced in the US or elsewhere in the world. Human health is more affected by the precursors to acid deposition such as sulfur dioxide and nitrogen oxides.

How does photochemical smog form?

Forms in the presence of sunlight. If there is an abundance of nitrogen oxides in the atmosphere, but very few VOCs, ozone forms. A few hours later when sunlight intensity decrease, nitrogen oxide is still present in the atmosphere and the ozone recombines with the NO and reforms into O2+ NO2. When petrochemicals or VOCs form human activity are absent or limited, the cycle of ozone formation and destruction generally takes place on a daily basis with relatively small amounts of photochemical smog formation.

What are the major air pollutants?

Major air pollutants include: sulfur dioxide, nitrogen oxides, carbon oxides, particulate matter, lead, ozone, VOCs, and mercury. Each pollutant has different way its emitted into the atmosphere. They also have different effects. A lot of them are bad for humans respiratory systems as well.

What are the two primary pollutants that lead to the formation of acid deposition?

Nitrogen oxides and sulfur dioxide are released into the atmosphere as a result of numerous natural and anthropogenic combustion processes. In the presence of atmospheric oxygen and water, these primary pollutants are transformed, through a series of reactions, into the secondary pollutants nitric acid and sulfuric acid. The latter compounds break down further, producing nitrate, sulfate, and hydrogen ions that generate the acidity in acid deposition.

What is sick building syndrome?

Often in new or renovated buildings sick building syndrome occurs. This is because new buildings contain many products made with synthetic materials and glues that may not have full dried out. A significant amount of off-gassing occurs. A buildup of toxic compounds and pollutants in an airtight space; in buildings with good insulation and tight seal against air leaks, sick building syndrome can occur.

Describe pollution control methods for sulfur dioxide, nitrogen oxides, and particulates.

Pollution control methods include such devices: the baghouse filter, the electrostatic precipitator, and the scrubber. The baghouse filter removes particles by a series of filter bags that physically filter out the particles. In the electrostatic precipitator, particles are given a negative charge. This causes them to be attracted to a positively charge plate, where they are held. Periodically they are removed from the plate and collected for disposal. The scrubber is when particles are "scrubbed" from the exhaust stream by water droplets. A water-particle "sludge" is collected and processed for disposal.

Why is air pollution considered a global system?

Pollution in one region of the world can affect other regions of the wld (i.e. air pollution in Asia has been linked to acid rain on W coast of US)

haze

Reduced visibility

What is the major natural sources of air pollution?

Some of the natural sources of air pollution are organic compounds from plants, sea salt, suspended soils and dusts (e.g. from the Sahara). Other natural sources are released during catastrophes such as volcanic eruptions and forest fires.

particulate matter

Source: burning fossil fuels and diesel exhaust Effect: reduces visibility & respiratory irritation Reduction: filtering, electrostatic precipitators, alternative energy)

How does the stratospheric ozone layer form and why is it beneficial?

Stratospheric ozone forms and breaks down naturally in a closed-loop cycle. First, UV-C radiation breaks the bonds holding together the oxygen molecule (O2) leaving two free oxygen atoms. When it reacts with the free oxygen atoms formed in reaction 1 the result is ozone. The net result of these two reactions is that, in the presence of UV radiation, oxygen is converted to ozone. Ozone is broken down into O2 and free oxygen atoms when it absorbs both UV-C and UV-B light. The free oxygen atoms and molecular oxygen O2 may again react to produce ozone molecules; thus, ozone is continuously formed and continuously broken down in the presence of sunlight.

Explain the purpose of sulfur allowances and how they work.

Sulfur allowances are awarded annually to existing sulfur emitters proportional to the amounts of sulfur the were emitting before 1990. The emitters are not allowed to emit more sulfur than the amount for which they have permits. At the end of a given year, the emitter must possess a umber of allowances at least equal to its annual emissions. Sulfur allowances can be bought and sold on the open market by anyone. Overall, this reduces sulfur emissions.

How does the Clean Air Act regulate anthropogenic emissions?

The Clean Air Act and its various amendments require that the EPA establish standards to control pollutants that are harmful to "human health and welfare." The term human health means the health of the human population and includes the elderly, children, and sensitive populations such as those with asthma. The term welfare refers to visibility, the status of crops, natural vegetation, animals, ecosystems, and buildings. This act helps regulate anthropogenic emissions by simply setting standards.

What has caused the depletion of the ozone layer?

The formation of a stable molecule CL2 accuulates as atmospheric chlorine interacts with ice crystals. When the Sun reappears in the spring, UV radiation breaks down this molecule into CL again, which in turn catalyzes the destruction of ozone. The overall trend of decreasing stratospheric ozone concentration is not related to temperature, but is caused by the breakdown reactions described earlier that result from increased concentrations of chlorine in the atmosphere. Depletion of ozone layer lets UV-B rays reach earth's surface.

What steps are being taken to reduce ozone depletion?

There are many steps being taken to reduce ozone depletion. A series of increasingly stringent amendments were eventually signed by more than 180 countries. These amendments required the elimination of CFC production and use in the developed world by 1996. Although some developing nation were exempted from this strict deadline. In total, the protocol addressed 96 ozone-depleting compounds.

sick building syndrome

a buildup of toxic compounds and pollutants in an airtight space; seen in newer buildings with good insulation and tight seals against air leaks

photochemical oxidants

a class of air pollutants formed as a result of sunlight acting on compounds such as nitrogen oxides

smog

a mixture of photochemical oxidants and particulate matter that causes a hazy view and reduced sunlight, and harm to the human respiratory system

List common sources of indoor air pollution in the developed world. What are the main sources of indoor pollution in the developing world?

developed- 1.)smoke from cigarettes 2)VOCs from paint, cleaners, and furniture 3)radon 4) mildew in showers dust mites 5)animal fur and dander developing: smoke and soot from burning wood, charcoal, dung, or crop waste We can use hybrid vehicles, trap methane before it releases into the air, use turbines for electricity, and help developing countries financially. People can also purchase the $50 solar cooker (developing countries)

primary pollutants

polluting compounds that come directly out of the smokestack, exhaust pipe, or natural emission source

secondary pollutants

primary pollutants that have undergone transformation in the presence of sunlight, water, oxygen, or other compounds

photochemical smog

smog dominated by oxidants such as ozone; also know as Los Angeles-type smog and brown smog

Sulfurous smog

smog dominated by sulfur dioxide and sulfate compounds; also known as gray smog or London-type smog

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

inversion layer

the layer of warm air that traps emissions in a thermal inversion

What are the major sources of anthropogenic air pollution?

transportation, fuel combustion in stationary sources, a variety of industrial processes, solid waste disposal and miscellaneous sources such as agricultural activities