Pollution in the atmosphere

Question 1

What are pollutants?

Answer 1

At certain times or places, the troposphere contains natural and human-caused gases, particles, and other substances in amounts that are harmful to humans or cause environmental damage.

Question 2

What are some sources of natural pollutants?

Answer 2

Natural sources produce greater quantities of air pollutants—nitrogen oxides, carbon monoxide, hydrocarbons from plants and trees, and carbon dioxide—than do sources attributable to humans. Volcanoes, forest fires, and dust storms are the most significant sources, based on the volume of smoke and particulates produced and blown over large areas. However, pollen from crops, weeds, and other plants can also cause high amounts of particle pollution, triggering asthma as well as other adverse human health effects.

Question 3

What are the particulates produces by natural pollution events called?

Answer 3

The particulates produced by these events are also known as aerosols and include the liquid droplets and suspended solids that range in size from visible water droplets and pollen to microscopic dust.

Question 4

What eruption in 1991 was a dramatic natural source of air pollution?

Answer 4

A dramatic natural source of air pollution was the 1991 eruption of Mount Pinatubo in the Philippines (discussed in Chapter 1), probably the 20th century’s second-largest eruption. This event injected about 18 million tonnes of sulfur dioxide (SO2) into the stratosphere. The spread of these emissions is shown in a sequence of satellite images

Question 5

How do wildfires affect air pollution?

Answer 5

Wildfires are another source of natural air pollution and occur frequently on several continents (Figure 3.5). Soot, ash, and gases darken skies and impair human health in affected regions. Wind patterns can spread the pollution from the fires to nearby cities, closing airports and forcing evacuations to avoid the health-related dangers. Satellite data show smoke plumes travelling horizontally for distances up to 1600 km. Smoke, soot, and particulates can be propelled vertically as high as the stratosphere.

Question 6

What is the connection between climate change and wild fire occurrence?

Answer 6

In 2006, scientists established a connection between climate change and wildfire occurrence in the western United States, where higher spring and summer temperatures and earlier snowmelt result in a longer fire season. These connections are valid for Canada (see Chapter 5 Geosystems Now), and indeed occur across the globe, as in drought-plagued Australia, where thousands of wildfires burned millions of hectares in recent years.

Question 7

What is the Anthropogenic atmosphere ?

Answer 7

Earth’s future atmosphere, so named because humans appear to be the principal causative agent.

Question 8

How many deaths dose air pollution cause worldwide?

Answer 8

Anthropogenic air pollution remains most prevalent in urbanized regions. According to the World Health Organization, urban outdoor air pollution causes an estimated 1.3 million deaths worldwide.

Question 9

Describe Carbon monoxide

Answer 9

CO

Incomplete combustion of fuels, mainly vehicle emissions

Odourless, colourless, tasteless gas. Toxic due to affinity for hemoglobin. Displaces O2 in bloodstream; 50 to 100 ppm causes headaches and vision and judgment losses.

Question 10

Nitrogen oxides

Answer 10

NOx (NO, NO2)

Agricultural practices, fertilizers, and high temperature/pressure combustion, mainly from vehicle emissions

Reddish-brown choking gas. Inflames the respiratory system, destroys lung tissue. Leads to acid deposition.

Question 11

Volatile organic compounds

Answer 11

VOCs

Incomplete combustion of fossil fuels such as gasoline; cleaning and paint solvents

Prime agents of surface ozone formation.

Question 12

Ozone

Answer 12

O3

Photochemical reactions related to motor vehicle emissions

Highly reactive, unstable gas. Ground-level ozone irritates human eyes and respiratory system. Damages plants.

Question 13

Peroxyacetyl nitrates

Answer 13

PANs

Photochemical reactions related to motor vehicle emissions

No human health effects. Major damage to plants, forests, crops.

Question 14

Sulfur oxides

Answer 14

SOx (SO2, SO3)

Combustion of sulfur-containing fuels

Colourless, but with irritating smell. Impairs breathing and taste threshold. Causes human asthma, bronchitis, emphysema. Leads to acid deposition.

Question 15

Particulate matter

Answer 15

PM

Industrial activities, fuel combustion, vehicle emissions, agriculture

Complex mixture of solid and liquid particles including dust, soot, salt, metals, and organics. Dust, smoke, and haze affect visibility. Black carbon may have a critical role in climate change. Various health effects: bronchitis, pulmonary function.

Question 16

Carbon dioxide

Answer 16

CO2

Complete combustion of fossil fuels

Principal greenhouse gas

Question 17

What contributes the most Sulfur oxides and particulates?

Answer 17

Stationary pollution sources, such as electric power plants and industrial plants that use fossil fuels, contribute the most sulfur oxides and particulates. Concentrations are focused in the Northern Hemisphere, especially over eastern China and northern India.

Question 18

What is the major component of anthropogenic air pollution?

Answer 18

Although not generally present in human environments until the advent of the automobile, photochemical smog is now the major component of anthropogenic air pollution; it is responsible for the hazy sky and reduced sunlight in many of our cities

Question 19

What is Photochemical smog?

Answer 19

Photochemical smog results from the interaction of sunlight and the combustion products in automobile exhaust, primarily nitrogen oxides and volatile organic compounds (VOCs), such as hydrocarbons that evaporate from gasoline. Although the term smog—a combination of the words smoke and fog—is generally used to describe this pollution, this is a misnomer.

Question 20

How is NO2 produced and how dose it affect air quality?

Answer 20

The high temperatures in automobile engines produce nitrogen dioxide (NO2), a chemical also emitted to a lesser extent from power plants. NO2 is involved in several important reactions that affect air quality:

Interactions with water vapour to form nitric acid (HNO3), a contributor to acid deposition by precipitation, the subject of Focus Study 3.2.

Interactions with VOCs to produce peroxyacetyl nitrates, or PANs, pollutants that damage agricultural crops and forests, although they have no human health effects.

Interactions with oxygen (O2) and VOCs to form ground-level ozone, the principal component of photochemical smog.

Question 21

how car exhaust is converted into photochemical smog

Answer 21

. In the photochemical reaction, ultraviolet radiation liberates atomic oxygen (O) and a nitric oxide (NO) molecule from the NO2. The free oxygen atom combines with an oxygen molecule, O2, to form the oxidant ozone, O3. The ozone in photochemical smog is the same gas that is beneficial to us in the stratosphere in absorbing ultraviolet radiation. However, ground-level ozone is a reactive gas that damages biological tissues and has a variety of detrimental human health effects, including lung irritation, asthma, and susceptibility to respiratory illnesses.

Question 22

What is Industrial smog

Answer 22

Air pollution that is associated with coal-burning industries; it may contain sulfur oxides, particulates, carbon dioxide, and exotics

Question 23

How dose sulfur dioxide react in the environment.

Answer 23

Once in the atmosphere, sulfur dioxide (SO2) reacts with oxygen (O) to form sulfur trioxide (SO3), which is highly reactive and, in the presence of water or water vapour, forms tiny particles known as sulfate aerosols. Sulfuric acid (H2SO4) can also form, even in moderately polluted air at normal temperatures. Coal-burning electric utilities and steel manufacturing are the main sources of sulfur dioxide

Question 24

What is particulate matter?

Answer 24

The diverse mixture of fine particles, both solid and liquid, that pollute the air and affect human health is referred to as particulate matter (PM), a term used by meteorologists and regulatory agencies such as the Meteorological Service of Canada and the U.S. Environmental Protection Agency. Other scientists refer to these particulates as aerosols. Examples are haze, smoke, and dust, which are visible reminders of particulates in the air we breathe.

Question 25

What is Black Carbon?

Answer 25

Black carbon, or “soot,” is an aerosol having devastating health effects in developing countries, especially where people burn animal dung for cooking and heating. This fine particulate is not necessarily prevalent over urban areas; black carbon is mainly produced in small villages, but winds can spread it over the globe. In Africa, Asia, and South America, cooking stoves produce the highest concentrations, with diesel engines and coal plants having a smaller role. Black carbon is both an indoor and outdoor pollutant, made up of pure carbon in several forms; it absorbs heat in the atmosphere and changes the reflectivity of snow and ice surfaces, giving it a critical role in climate change

Question 26

What is PM2.5

Answer 26

PM2.5 is the designation for particulates 2.5 microns (2.5 μm) or less in diameter; these pose the greatest health risk. Sulfate aerosols are an example, with sizes about 0.1 to 1 μm in diameter. For comparison, a human hair can range from 50 to 70 μm in diameter. These fine particles, such as combustion particles, organics (biological materials such as pollens), and metallic aerosols, can get into the lungs and bloodstream.

Question 27

What is PM0.1

Answer 27

New studies are implicating even smaller particles, known as ultrafines at a size of PM0.1, as a cause of serious health problems. These are many times more potent than the larger PM2.5 and PM10 particles because they can get into smaller channels in lung tissue and cause scarring, abnormal thickening, and damage called fibrosis.

Question 28

What are some important factors that effect atmospheric contaminants?

Answer 28

The problems resulting from both natural and anthropogenic atmospheric contaminants are made worse by several important natural factors. Among these, wind, local and regional landscape characteristics, and temperature inversions in the troposphere dominate

Question 29

How dose Wind effect pollutants?

Answer 29

Winds gather and move pollutants, sometimes reducing the concentration of pollution in one location while increasing it in another. Dust, defined as particles less than 62 μm, is often moved by wind, sometimes in dramatic episodes.

Question 30

How do local and regional landscapes effect air pollutants?

Answer 30

Local and regional landscapes are another important factor affecting the movement and concentration of air pollutants. Mountains and hills can form barriers to air movement or can direct the movement of pollutants from one area to another. Some of the worst air quality results when local landscapes trap and concentrate air pollution.

Question 31

What is a temperature inversion and how dose it worsen pollution conditions?

Answer 31

Vertical differences in temperature and atmospheric density in the troposphere also can worsen pollution conditions. A temperature inversion occurs when the normal temperature, which usually decreases with altitude (normal lapse rate), reverses trend and begins to increase at some point. This can happen at any elevation from ground level to several thousand metres.

Figure 3.7 (page 84) compares a normal temperature profile with that of a temperature inversion. In the normal profile (Figure 3.7a), air at the surface rises because it is warmer (less dense) than the surrounding air. This ventilates the valley and moderates surface pollution by allowing air at the surface to mix with the air above. When an inversion occurs, colder (more dense) air lies below a warmer air layer (Figure 3.7b) that halts the vertical mixing of pollutants with other atmospheric gases. Thus, instead of being carried away, pollutants are trapped under the inversion layer.