The Atmosphere, Air Quality and Pollution Control

Question 1

Smog

Answer 1

a mix of air pollutants from fossil fuel combustion; worse in mountainous areas where it becomes trapped and in sunny/high altitude areas where solar radiation is intense; worst issues in the United States in Los Angeles now

Question 2

Mexico City smog case study

Answer 2

once had the worst air in the world but in the 1990s combatted smog issues; shut down an oil refinery, pushed for natural gas usage, removed lead from gasoline, decreased the sulfur content of diesel, and used catalytic converters in new vehicles; implemented emissions testing, built air quality sampling stations and enforced cleaner taxis and city vehicles as the population was still growing; in 2007 created a 15-year plan to construct new subway system lines, fuel-efficient buses, electric buses/taxis, and car- and bicycle-sharing programs + restricted car traffic on Sundays in the main area of the city; most pollutants dropped 75% between 1991 and 2010-2015 but issues persist (rampant development, complacent politicians, hot and windless weather brings bad conditions back and smog still contributes to 4000 deaths per year)

Question 3

Atmosphere

Answer 3

the layer of gases that envelops a planet; in the case of Earth it moderates climate, provides oxygen, shields against meteors + solar radiation, and transports/recycles water + nutrients

Question 4

Content of Earth’s atmosphere

Answer 4

78% nitrogen, 21% oxygen, 1% other gases (argon, neon, helium, etc.); water vapor varies by time and place between 0-4%

Question 5

Proportion of Earth’s diameter taken up by the atmosphere

Answer 5

1/100

Question 6

Troposphere

Answer 6

the bottommost layer of Earth’s atmosphere where air movement drives weather and climate; 11 km average height; thin but contains 3/4 of the atmosphere’s mass (due to gravity); gets colder with increasing altitude

Question 7

Tropopause

Answer 7

the dividing area between the troposphere and the stratosphere

Question 8

Stratosphere

Answer 8

the second lowest layer of Earth’s atmosphere that is similar in composition to the troposphere but drier and less dense; 11-50 km above sea level; pollutants tend to last within it as there is little vertical mixing of gases; gets warmer with increasing altitude because of oxygen and ozone that absorb UV radiation

Question 9

Ozone layer

Answer 9

part of the atmosphere containing most atmospheric ozone; 17-30 km above sea level (so within the stratosphere); absorbs and scatters UV so less reaches the surface; life depends upon it

Question 10

Mesosphere

Answer 10

second highest layer of Earth’s atmosphere where meteors burn up; gets colder with increasing altitude

Question 11

Thermosphere

Answer 11

highest layer of Earth’s atmosphere; gets warmer with increasing altitude; extends up to 500 km above sea level before merging with space in the exosphere

Question 12

Percentage of solar energy absorbed vs. reflected

Answer 12

70% absorbed (by the atmosphere and the surface), 30% reflected

Question 13

Effects of radiation absorption by land and surface water

Answer 13

emit thermal infrared radiation as a result (and some water evaporates), making lower altitudes warmer and more moist

Question 14

Convective circulation

Answer 14

an air movement pattern controlled by radiation absorption on the Earth’s surface; warm air rises because it is less dense and creates vertical currents; in areas with lower pressure warm air expands and cools and its moisture condenses to rain; cool air descends and becomes denser + replaces warm rising air, then picks up heat and moisture (and the cycle continues)

Question 15

Weather

Answer 15

atmospheric conditions in a location over minutes, hours, days or weeks

Question 16

Climate

Answer 16

typical patterns of atmospheric conditions in a location over years, decades, centuries or millennia

Question 17

What characteristic of an atmospheric layer causes it to have vertical mixing?

Answer 17

cooler temperatures as altitude increases (since warm air rises)

Question 18

Temperature inversion (AKA thermal inversion)

Answer 18

a departure from a normal temperature profile where warm and cool layers of air are in the opposite order (cool below warm), such as in mountain valleys where the slopes block sunlight and keep low air shaded/cool or as with cooled ocean air moving inland; can cause pollutants to be trapped at low altitudes (usually mixing dilutes them and carries them upward)

Question 19

Inversion layer

Answer 19

a band of air where temperature increases with altitude (since the direction of temperature change is switched)

Question 20

Cool air characteristics (compared to warm)

Answer 20

denser, more stable, resists mixing; why inversions occur

Question 21

Hadley cells

Answer 21

convective cells of air at the equator where the sun is most intense; air warms, rises and expands, then releases moisture as heavy rainfall (as in tropical rainforests)

Question 22

Air at 30° north and south latitude

Answer 22

air that diverged from the equator and cooled/sank with rainfall (so now dry); line up with deserts

Question 23

Ferrel and polar cells

Answer 23

cells of air that lift up and create precipitation at 60° north and south latitude; descends again at the poles

Question 24

Characteristics of air from the equator to the poles

Answer 24

wet –> arid –> moist –> dry; explains (in conjunction with temperature variation) why biomes occur in latitudinal bands

Question 25

Formation of global wind currents

Answer 25

due to the movement of cells of air and the Coriolis effect (how Earth’s rotation affects the movement of things around it)

Question 26

Coriolis effect

Answer 26

describes how regions of the Earth’s surface near the equator move west to east more quickly than those near the poles due to the Earth’s rotation; an observer on Earth finds that currents going north or south seem to be deflected from a straight path and are instead curved

Question 27

Air pollutants

Answer 27

gases and particulate materials added to the atmosphere that can affect the climate and harm living things (including wood fires to coal-burning power plants)

Question 28

Air pollution

Answer 28

the release of air pollutants

Question 29

Outdoor air pollution (AKA ambient air pollution)

Answer 29

refers to air pollution taking place outside in the open atmosphere on larger scales; has mostly decreased in industrialized nations with public policy and technology changes but is still a major issue in developing and urban areas; includes greenhouse gases

Question 30

World Health Organization’s estimate of premature deaths per year due to health problems from outdoor air pollution

Answer 30

3.3 million

Question 31

Natural processes that contribute to air pollution

Answer 31

fires (soot and gases from typically 60 million hectares per year), volcanic eruptions (particles + sulfur dioxide + ash), windblown dust and dust storms; some are worse due to human activity and land use policies (e.g., farming and grazing strip vegetation so dust storms increase, fires are used to clear forests, suppressing fires leads to fuel buildup so fires are more destructive, and fossil fuel use leads to warming and drought so dust storms and fires are more common)

Question 32

Primary pollutants

Answer 32

released directly from a source

Question 33

Secondary pollutants

Answer 33

formed by interactions between pollutants or a pollutant and the atmosphere (e.g., ozone from smog and acid precipitation from pollution/water/oxygen)

Question 34

Residence time

Answer 34

how long a substance lasts in the atmosphere; some react or settle to the ground more readily than others; short = localized impact for a short period (e.g., car exhaust) and long = regional/global impact for long periods, even centuries (e.g., the pollution driving climate change or ozone depletion)

Question 35

Clean Air Act

Answer 35

U.S. legislation from 1963 that funds pollution control research, sets air quality standards, encourages emissions standards for automobiles and stationary point sources, imposes limits on new sources, funds a nationwide monitoring system and enables citizens to sue parties that violate it; had the EPA set standards for the emissions of key pollutants and the concentrations of major pollutants in ambient air; required states to monitor and develop/enforce regulations, then submit their plans to the EPA (which can then take over if these are found to be inadequate and prevent states from receiving transportation project funding when the air is not clean enough)

Question 36

Which 6 major pollutants do state and local agencies have to monitor and report about to the EPA?

Answer 36

carbon monoxide, sulfur dioxide, nitrous oxides, volatile organic compounds, particular matter and lead

Question 37

About carbon monoxide as a pollutant

Answer 37

colorless and odorless gas; produced mainly by incomplete fuel combustion (especially in vehicles and engines in the U.S.) but also from industrial processes, waste combustion and residential wood burning; binds to hemoglobin in the blood and keeps it from binding with oxygen (poisonous)

Question 38

About sulfur dioxide as a pollutant

Answer 38

pungent and colorless gas; mostly from the combustion of coal for electricity and industry (sulfur is a contaminant in coal and reacts with oxygen); can react to form sulfur trioxide and sulfuric acid in the atmosphere, leading to acid deposition

Question 39

About nitrous oxides as pollutants

Answer 39

mostly come from diatomic oxygen and nitrogen in the atmosphere reacting at high temperatures in vehicle engine combustion; rest from industry and electrical utilities; contribute to smog, acid deposition and stratospheric ozone depletion

Question 40

About volatile organic compounds (VOCs) as pollutants

Answer 40

emitted by engines, solvents, industrial processes, household chemicals, paints, plastics and consumer items; include benzene, acetone, formaldehyde, etc. (one anthropogenic group is the hydrocarbons); some are emitted naturally by plants; produce secondary pollutants

Question 41

About particulate matter as a pollutant

Answer 41

refers to solid and liquid particles small enough to be suspended in the atmosphere; primary pollutants in this category include dust, soot, etc. and secondary pollutants include sulfates, nitrates, etc.; classified by size (PM₁₀ < 10 microns in diameter, mostly from road dust and PM₂.₅ < 2.5 microns in diameter, mostly from combustion); smaller particles can get deep into the lungs and tissues and cause organ damage

Question 42

About lead as a pollutant

Answer 42

a heavy metal and a particle pollutant; tetraethyl lead and tetramethyl lead improve engine performance when used in gasoline but particles become airborne and are inhaled or end up on land/in water; accumulates in tissues once it enters the food chain and causes nervous system malfunction among other issues; leaded gas has mostly been phased out since the 1980s so the main source in developed areas now is industrial metal smelting

Question 43

Social demand, policy and technology have greatly decreased the presence of the 6 major air pollutants despite what factors?

Answer 43

population growth, increased energy use, increased miles traveled by vehicle and higher GDP