The Atmosphere, Air Quality and Pollution Control Flashcards
Smog
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
Mexico City smog case study
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)
Atmosphere
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
Content of Earth’s atmosphere
78% nitrogen, 21% oxygen, 1% other gases (argon, neon, helium, etc.); water vapor varies by time and place between 0-4%
Proportion of Earth’s diameter taken up by the atmosphere
1/100
Troposphere
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
Tropopause
the dividing area between the troposphere and the stratosphere
Stratosphere
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
Ozone layer
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
Mesosphere
second highest layer of Earth’s atmosphere where meteors burn up; gets colder with increasing altitude
Thermosphere
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
Percentage of solar energy absorbed vs. reflected
70% absorbed (by the atmosphere and the surface), 30% reflected
Effects of radiation absorption by land and surface water
emit thermal infrared radiation as a result (and some water evaporates), making lower altitudes warmer and more moist
Convective circulation
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)
Weather
atmospheric conditions in a location over minutes, hours, days or weeks
Climate
typical patterns of atmospheric conditions in a location over years, decades, centuries or millennia
What characteristic of an atmospheric layer causes it to have vertical mixing?
cooler temperatures as altitude increases (since warm air rises)
Temperature inversion (AKA thermal inversion)
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)
Inversion layer
a band of air where temperature increases with altitude (since the direction of temperature change is switched)
Cool air characteristics (compared to warm)
denser, more stable, resists mixing; why inversions occur
Hadley cells
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)
Air at 30° north and south latitude
air that diverged from the equator and cooled/sank with rainfall (so now dry); line up with deserts
Ferrel and polar cells
cells of air that lift up and create precipitation at 60° north and south latitude; descends again at the poles
Characteristics of air from the equator to the poles
wet –> arid –> moist –> dry; explains (in conjunction with temperature variation) why biomes occur in latitudinal bands
Formation of global wind currents
due to the movement of cells of air and the Coriolis effect (how Earth’s rotation affects the movement of things around it)
Coriolis effect
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
Air pollutants
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)
Air pollution
the release of air pollutants
Outdoor air pollution (AKA ambient air pollution)
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
World Health Organization’s estimate of premature deaths per year due to health problems from outdoor air pollution
3.3 million
Natural processes that contribute to air pollution
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)
Primary pollutants
released directly from a source
Secondary pollutants
formed by interactions between pollutants or a pollutant and the atmosphere (e.g., ozone from smog and acid precipitation from pollution/water/oxygen)
Residence time
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)
Clean Air Act
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)
Which 6 major pollutants do state and local agencies have to monitor and report about to the EPA?
carbon monoxide, sulfur dioxide, nitrous oxides, volatile organic compounds, particular matter and lead
About carbon monoxide as a pollutant
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)
About sulfur dioxide as a pollutant
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
About nitrous oxides as pollutants
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