Environmental Science Test 3

Formula for photosynthesis

6CO2 + 6H2O + solar energy → C6H12O6 + 6O2

the top four gases make up

99.998 % of the volume of clean dry air

Gt = gigatonne

= 109 metric tons = 1015 g

particulate matter

(PM), sometimes known simply as "particulates" refers to solid particles and liquid droplets suspended in the air we breathe. Particulate pollution is made up of a variety of components, including acids (nitrates and sulfates), organic chemicals, metals, soil or dust particles, and allergens (pollen and mold spores). The size of the particles in directly linked to their potential for causing health problems. P articles that are 10 micrometers in diameter or smaller generally pass through the throat and nose and enter the lungs.

Water Vapor

(water in a 'gas' state) is usually present up to about 4% of the total volume depending on location. In the Earth's desert regions (30° N/S) when dry winds are blowing, the water vapor contribution to the composition of the atmosphere will be near zero.

Stratosphere

- extends from tropopause to 50-53 KM above earths surface -similar proportions of most gasses as troposphere with two major exceptions 1) there is almost no water vapor in the stratosphere 2) the stratosphere has nearly 1,000 times more ozone (O3) than the troposphere. -19 percent of total mass of atmosphere -temperature in this region increases with height as a result of heat that is produced during the formation of ozone This heat is responsible for temperature increases from an average -51 °C (-60°F) at tropopause to a maximum of about -15°C (5°F) at the top of the stratosphere. This increase in temperature with height means warmer air is located above cooler air. This prevents "convection" as there is no upward vertical movement of the gases. The consequence of this little to no mixing of gases in the stratosphere makes it relatively calm but also means that once substances such as pollutants enter this zone, they can remain suspended for many years

Ocean-atmosphere exchange

-CO2 dissolves readily in water. -Exchange of carbon across the atmosphere-ocean interface links the terrestrial and aquatic carbon cycles. -Oceans are a sink for CO2 produced by fossil fuel combustion.

Carbon Reservoir

A natural feature, such as a rock, a pinch of soil, or an organism, that stores carbon-containing molecules and exchanges them with other carbon reservoirs.

Carbon flux

Amount of carbon exchanged between earth's carbon pools per unit time

thermal expansion

An increase in the size of a substance when the temperature is increased

Chrloroplast

Chloroplasts visible in freshwater algae. Chloroplasts are green in color due to the chlorophyll a they contain, and are the site of photosynthesis. Chlorophyll a is the green pigment that allows plants, algae, and cyanobacteria to absorb the energy they need for photosynthesis from sunlight. a)

If each chlorine atom released from a CFC molecule destroyed only one ozone molecule, CFCs would pose very little threat to the ozone layer. However, when a chlorine monoxide molecule encounters a free atom of oxygen, the oxygen atom breaks up the chlorine monoxide, stealing the oxygen atom and releasing the chlorine atom back into the stratosphere to destroy another ozone molecule. These two reactions happen over and over again, so that a single atom of chlorine, acting as a catalyst, destroys many molecules (about 100,000) of ozone

Crazy

Lithosphere and ocean are largest carbon reservoirs

Each of these reservoirs holds more carbon than all of the other reservoirs combined. Much of the carbon stored in these reservoirs, especially deep in the lithosphere or in deep ocean environments, has an extremely long residence time, and does not actively participate in rapid fluxes. The notable exceptions here, of course, are fossil fuels, which are mined by humans and converted into gaseous forms of carbon through combustion.

The Montreal Protocol

International policy efforts to restrict production of ozone depleting CFCs culminated in the 1987 treaty known as the Montreal Protocol in which signing nations agreed to cut CFC production in half by 1998. At least five follow-up agreements since then helped to deepen the cuts, advanced timetables for compliance, and addressed additional ozone-depleting substances such as halons, methyl chloroform, carbon tetrachloride, and hydrochlorofluorocarbons (HCFCs) Most countries around the world have phased out production of the substances covered by the agreements and industry has been able to shift to safer alternative chemicals. As a result, there's evidence that the Antarctic ozone hole has stopped growing worse, although recovery is not expected anytime soon. Phasing out CFCs and HCFCs is also beneficial in protecting the earth's climate, as these substances are also very damaging greenhouse gases.

Milankovitch cycles

Milankovitch cycles describe the very slight "wobbles" that occur in the Earth's tilt and path as it moves around the sun. The Earth is always slightly tilted on its axis with respect to the sun. The angle of this tilt, however, changes periodically, varying from about 22° to about 25°. A less severe tilt will cause milder summers

Mobile (non point)

Mobile sources of air pollutants move from place to place while emitting pollutants. Examples of mobile sources include vehicles, aircrafts, ships, and trains.

Ozone is "good" in the stratosphere because it absorbs most ultraviolet radiation. Ozone is "bad" in the troposphere because it is harmful to breathe and is the primary component of smog in summer.

NASA

enteric fermentation

One example of the impacts of industrialized agriculture is the production of methane (CH4), a potent greenhouse gas. You will learn more about methane later in this section. As you saw earlier, methane is a common product of anaerobic metabolisms. The gut of ruminant animals (such as sheep, cattle, and goats) has evolved to allow the animals to digest the very tough carbon molecules, such as cellulose, in grass. They do this through symbiosis, or cooperation, with anaerobic bacteria who live in the gut tract. These anaerobic bacteria produce methane and other gases as a result of their metabolism when they Figure 6.5. US methane emissions by source. 36% of the US methane production comes from agriculture: enteric fermentation (production of methane by anaerobic bacteria within the ruminant gut) and manure management. All emissions estimates from the Inventory of US Greenhouse Gas Emissions and Sinks: 1990-2013. US EPA. 11 break down molecules like cellulose.

human contribution to carbon cycle

Our body takes the carbon molecules contained in this biomass, and uses them, along with the oxygen we breathe in, for cellular respiration to create the adenosine triphosphate (ATP) we need for energy. The products of cellular respiration include the CO2 we exhale, water, and energy that is stored in ATP

The Ozone Layer

Ozone makes up a very small proportion of the gases in our atmosphere and most of it is concentrated in a portion of the stratosphere roughly 17 - 30 km above the surface. This region, called the ozone layer, acts as a protective shield that protects life on the surface of the Earth by absorbing most of the harmful portions of the high-energy UV radiation coming from the sun.

Concentrations of ozone are measured in

Parts per billion Scientists have been measuring ozone since the 1920's using ground-based instruments that look skyward. Satellite measurements of concentrations of atmospheric ozone began in 1970 and continue today

Photosynthesis

Photosynthetic organisms, such as plants, algae, and cyanobacteria, bring in CO2 from the atmosphere and, using energy from the sun, convert CO2 and water into glucose molecules (organic carbon). The products of photosynthesis are oxygen and glucose (Equation 6.1). These glucose molecules are simple sugars that autotrophs ("self-feeders") can "burn" for energy, or transform into other usable carbon molecules through the process of cellular respiration (described in the next paragraph), or to build plant biomass. Photosynthesis takes place in organelles called chloroplasts, shown in Figure 6.2. Photosynthesis accounts for 123 Gt of C per year that is removed from the atmosphere and stored in plant biomass. Such a massive amount of photosynthesis occurs on Earth that no other single flux moves as much carbon in the same timeframe.

acid rain

Rain containing acids that form in the atmosphere when industrial gas emissions (especially sulfur dioxide and nitrogen oxides) combine with water.

Stationary (Point) outdoor air pollutants

Stationary sources have a fixed location, for example power plant smokestacks, burning, construction sites, farmlands and surface mines among others

Sulfer Dioxide (SO2)

Sulfur dioxide is one of a group of highly reactive gasses known as "oxides of sulfur." The largest sources of SO2 emissions are from fossil fuel combustion at power plants (73%) and other industrial facilities (20%). Smaller sources of SO2 emissions include industrial processes such as extracting metals from their ores, and the burning of high sulfur containing fuels by locomotives, large ships, and non-road equipment.

All of the carbon that is currently stored in all of the vegetation on Earth got there through the process of photosynthesis.

T

In both developed and developing nations, indoor air pollution poses a greater health risk than outdoor air pollution.

T

thermal equilibrium temperature

The Earth receives energy from the sun and in turn radiates energy back into space. When these two energies are equal, a stable temperature of the Earth is achieved. This temperature 12 can be calculated from basic physics and is equal to about -18°C (0°F) 59 on surface

Stratopause

The boundary between the stratosphere and the mesosphere

One class of greenhouse gas chemicals that has no natural sources is the fluorinated gases.

These include HFCs, PFCs, and SF6, among others. Because these are synthetic chemicals that are only created by humans, these gases were essentially non-existent before the industrial revolution. These synthetic gases are used for a wide variety of applications, from refrigerants to semiconductor manufacturing, and propellants to fire retardants. They tend to have a long lifetime in the atmosphere

The Ozone Hole

This hole is a result of ozone depletion that occurs every year during the Antarctic spring (Figure 5.4) and was first reported to the public by the British Antarctic Survey in 1985. The thickness of the ozone layer above the Antarctic continued to decline while the geographic area covered by the ozone hole continued to increase, reaching its lowest concentration (thickness) in 1994 and largest geographic area in 2000. Recent data shows that ozone concentration globally and in the Arctic and Antarctic is no longer declining.

Thermospehere

This layer is known as the upper atmosphere. Unlike the mesosphere, the gases in this layer readily absorb incoming high energy ultraviolet and x-ray radiation from the sun. Because of this absorption, the temperature in the thermosphere increases with height and can reach as high as 2,000°C (3,600°F) near the top depending on solar activity. However, despite the high temperature, this layer of the atmosphere would still feel very cold to our skin due to the very thin atmosphere. The high temperature indicates the amount of energy absorbed by molecules but with so few in this layer, the total number of molecules is not enough to heat our skin. There's no sharp boundary that marks the end of the atmosphere. Pressure and density simply continue to decrease with distance until they become indistinguishable from the near-vacuum of outer space.

Ozone-Oxygen Cycle

This occurs as ozone and oxygen atoms are continuously inter-converted from energy generated by UV rays in the upper atmosphere.

toxic pollutants

Toxic air pollutants, also known as hazardous air pollutants, are those pollutants that are known or suspected to cause cancer or other serious health effects, such as reproductive effects or birth defects, or adverse environmental effects. Examples of toxic air pollutants include benzene, which is found in gasoline; perchloroethylene, which is emitted from some dry cleaning facilities; methylene chloride, which is used as a solvent and paint stripper by a number of industries; and others such as dioxin, asbestos, toluene, and metals such as cadmium, mercury, chromium, and lead compounds. Mercury can get in plants eaten by animals then we eat them

UV-A

UV-A is the least energetic and least harmful but can cause some damage to living cells, resulting in sunburns and skin damage UV-A is also not absorbed by ozone in the stratosphere and is therefore transmitted through the atmosphere to the surface of the Earth

UV-C

UV-C is the most harmful and most energetic of all UV, but is strongly absorbed in both the thermosphere and the stratosphere and does not make it to the Earth's surface. UV-C is the one responsible for the splitting of oxygen molecules in the stratosphere that leads to the formation of ozone. When ozone absorbs UV it regenerates oxygen atoms and releases heat which warms the upper part of the stratosphere

Natural sources of VOCs include plants, the largest source, and bacteria in the guts of termites and ruminant animals. These compounds are generally oxidized to carbon monoxide and carbon dioxide in the atmosphere. VOCs are of great concern because they are precursors for the formation of ozone, a secondary air pollutant.

VOC INFO

Greenhouse gases

While you already know about the "big three" greenhouse gases (CO2, CH4, and N2O), it's important to realize that water vapor (H2O) is also a greenhouse gas. While humans have little direct impact on water vapor concentrations in the atmosphere, is it still an essential component of the natural greenhouse effect that occurs in our atmosphere.

Argon

a non-reactive gas and we use it in light bulbs, in double-pane windows, and to preserve priceless documents such as the original Declaration of Independence and the Constitution

A model is

a projection of what might happen in the future based on knowledge of current and past events.

Tropopause

a sharp boundary at the top of the troposphere that limits mixing between the troposphere and the upper layers.

Clean Air Act

adding provisions for protection of the ozone layer. Most importantly, the amended Act required the gradual end to the production of chemicals that deplete the ozone layer. The Clean Air Act amendments passed by Congress requires the Environmental Protection Agency (EPA) to develop and implement regulations for the responsible management of ozone-depleting substances in the United States. Under the Clean Air Act, EPA has created several regulatory programs to address numerous issues, including: ending the production of ozone-depleting substances, • ensuring that refrigerants and halon fire extinguishing agents are recycled properly, • identifying safe and effective alternatives to ozone-depleting substances, 10 • banning the release of ozone-depleting refrigerants during the service, maintenance, and disposal of air conditioners and other refrigeration equipment, • requiring that manufacturers label products either containing or made with the most harmful ozone depleting substances.

air pollution affects

aggravation of respiratory and cardiovascular diseases; decreased lung function; increased frequency and severity of respiratory symptoms such as difficulty breathing and coughing; increased susceptibility to respiratory infections; effects on the nervous system, including the brain, such as IQ loss and impacts on learning, memory, and behavior; cancer; and premature death.

Natural Ventilation

air moves through opened windows and doors

polar vortex

arctic air masses that in the winter become isolated from the rest of the atmosphere and circulate about the pole; the vortex rotates counterclockwise because of the rotation of the Earth in the Southern Hemisphere chlorine in the frozen ice particles react w ozone when the sun comes back slowly destroying the ozone... This isolation allows temperatures to drop low 7 enough to create ice crystals at high altitudes. Ozone, nitric acid, sulfuric acid and some chlorine containing molecules are absorbed on the surfaces of these ice particles. When the sun rises over the Antarctic in the southern spring (October), light rapidly releases free chlorine atoms into the stratosphere. The chlorine atoms react with ozone breaking it down to molecular oxygen and an oxygen atom. The polar vortex keeps the ozone-depleted air inside the vortex from mixing with the undepleted air outside the vortex, hence the formation of an ozone hole. Ozone concentration drops significantly during the Antarctic spring (October).

Volatile Organic Compounds (VOCs)

are carbon-containing chemicals emitted as gases from natural and human-made sources. N

Chlorofluorocarbons (CFCs)

are man-made compounds made up of chlorine, fluorine and carbon. These compounds were commonly used as propellants in everyday products such as shaving cream, hair spray, deodorants, paints and insecticides and as coolants in refrigerators and air conditioners. CFCs are extremely stable molecules and do not react with other chemicals in the lower atmosphere, part of the reason why they were considered a safe choice. Their stability means that they tend to remain in the atmosphere for a very long time. With the constant movement of air in the lower atmosphere, CFCs eventually make their way into the stratosphere. Exposure to ultraviolet radiation in the stratosphere breaks them apart, releasing chlorine atoms. Free chlorine (Cl) atoms then react with ozone molecules, taking one oxygen atom to form chlorine monoxide (ClO) and leaving an oxygen molecule (O2) (Figure 5.5). The ClO reacts with other atoms freeing up the Cl making it available to react with another ozone molecule, repeating the cycle over and over resulting in ozone depletion.

secondary pollutants

are produced through reactions between primary pollutants and normal atmospheric compounds. For example, ground-level ozone forms over urban areas through reactions, powered by sunlight, between primary pollutants (oxides of nitrogen) and other atmospheric gases such as VOCs.

Ground-level ozone (O3):

colorless gas w a sweet odor directly into the air, but is created by the interaction of sunlight, heat, oxides of nitrogen (NOx) and volatile organic compounds (VOCs). Ozone is likely to reach unhealthy levels on hot sunny days in urban environments. Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are some of the major sources of NOx and VOCs.

hydrochlorofluorocarbons (HCFCs)

compounds of hydrogen, chlorine, fluorine, and carbon

inhalable course particles

diameter larger than 2.5 micrometers and smaller than 10 micrometers come from road dust

fine particles

diameters that are 2.5 micrometers and smaller ... 30 times smaller Than average human hair. TINY come from combustion process

Nitrogen

dilutes oxygen and prevents rapid or instantaneous burning at the Earth's surface, as oxygen gas is a necessary reactant of the combustion process. Nitrogen is also needed and used by living things to make proteins, though as nitrogen gas, N2, it is unavailable to most living things

Air Pollution

dust storms, forest fires, and volcanic eruptions, or from human activities such as biomass burning, vehicular emissions, mining, agriculture, and industrial processes. Improved technology and government policies have helped reduce most types of outdoor air pollution in many industrialized countries including the United States, in recent decades. However, outdoor air quality is still a problem in less industrialized nations, especially in megacities of rapidly industrializing nations such as China and India.

Carbon can enter the oceans through two primary fluxes:

first through photosynthesis by algae (also called phytoplankton in Figure 6.1), and second through the chemical reaction of ocean-atmosphere exchange.

Dissolved CO2 is essential for many organisms

including shell-building animals and other organisms that form a hard coating on their exterior (e.g., shellfish, corals, Haptophyte algae). This hard coating is built out of aragonite, a mineral form of the molecule calcium carbonate, CaCO3. These organisms rely on the formation of carbonate ions (see Chapter 1 supplemental material for information on ions), CO32-, from dissolved CO2, through a natural, chemical reaction that occurs. This takes place through a chain-reaction equation, where bicarbonate (HCO3-) is formed as an intermediate, and hydrogen ions (H+) are generated (equations 6.3 and CO +

ozone depletion, consequently, leads to

increase in the amount of harmful UV-B radiation that reaches the Earth's surface and this what we are talking about when we discuss the ozone problem.

Changes to fluxes in the carbon cycle that humans are responsible for include

increased contribution of CO2 and other greenhouse gases to the atmosphere through the combustion of fossil fuels and biomass; increased contribution of CO2 to the atmosphere due to land-use changes; increased CO2 dissolving into the ocean through ocean-atmosphere exchange; and increased terrestrial photosynthesis.

Less industrialized countries

indoor air pollution is worse and the most common and dangerous types are carbon monoxide and soot

Outdoor air vs indoor

indoor is worse and people spend more time indoor.

immediate affects of air pollution

irritation of the eyes, nose, and throat, headaches, dizziness, and fatigue. Such immediate effects are usually short-term and treatable

Carbon Monoxide (CO)

is a colorless, odorless gas emitted from combustion processes, specifically, the incomplete combustion of fuel. Nationally and, particularly in urban areas, the majority of CO emissions to ambient air come from mobile sources. CO can cause harmful health effects by reducing oxygen delivery to the body's organs (like the heart and brain) and tissues. At extremely high levels, CO can cause death.

Lead (Pb)

is a metal found naturally in the environment as well as in manufactured products. The major sources of lead emissions have historically been from fuels in motor vehicles (such as cars and trucks) and industrial sources. As a result of EPA's regulatory efforts to remove lead from gasoline, emissions of lead from the transportation sector dramatically declined by 95 percent between 1980 and 1999, and levels of lead in the air decreased by 94 percent during that time period. The major sources of lead emissions today are ore and metal processing and piston-engine aircraft operating on leaded aviation gasoline. Today, the highest levels of lead in air are usually found near lead smelters.

Ozone (03)

is a molecule in which three atoms of oxygen are bonded together. The oxygen gas in the air we breathe has two oxygen atoms bonded together (O2). Ozone is relatively unstable and releases its third oxygen atom readily so it oxidizes and burns things more readily than oxygen gas. This characteristic makes ozone in the troposphere (ground-level ozone) an air pollutant (see section 5.3) but in the stratosphere, ozone is essential for protecting life on Earth. Ozone in the stratosphere is formed when an oxygen molecule (O2) is broken apart into two separate oxygen atoms (O) by high- energy ultra violet (UV) solar radiation. Each of the resulting oxygen atoms (O) in turn reacts with an oxygen molecule (O2) creating ozone (O3) (Figure 5.2). Once produced, ozone can absorb UV radiation 5 breaking the molecule to regenerate an oxygen molecule and a single oxygen atom. So, while ozone is continually being replenished, it is also continually being destroyed. If the rate of ozone creation is equal to the rate of destruction, the total amount will remain the same. Because there is so much oxygen in our atmosphere, this "ozone-oxygen cycle" is continuously absorbing UV radiation.

Radon

is a naturally occurring radioactive gas produced from the decay of uranium in rock. If a building/home is constructed in an area with uranium containing rock, the gas can seep through the foundations and accumulate in basements. Exposure to radon can cause lung cancer.

Nitrogen Dioxide (NO2)

is a yellowish-brown to reddish-brown foul-smelling gas that is a major contributor to smog and acid rain. Nitrogen oxides result when atmospheric nitrogen and oxygen react at the high temperatures created by combustion engines. Most emissions in the U.S. result from combustion in vehicle engines, electrical utility, and industrial combustion.

carbon dioxide

is an essential gas used for photosynthesis. This process is essential for other life as well because during photosynthesis, water molecules are split apart and their oxygen is released back to the atmosphere. Carbon dioxide also acts as a blanket that prevents the escape of heat into outer space

Photochemical smog

is formed when sunlight drives chemical reactions between primary pollutants from automobiles and normal atmospheric compounds. The product is a mix of over 100 different chemicals with the most abundant being ground-level ozone.

industrial smog

is produced primarily by the burning of fossil fuels which produces carbon dioxide (from complete combustion), carbon monoxides (from partial combustion), sulfur, and mercury. The sulfur reacts with other chemicals in the atmosphere producing several sulfur compounds including sulfur dioxide. These compounds along with particulate material make up industrial smog

Troposphere

is the lowest layer extending from the surface up to roughly 18 km above the surface depending on location (varies from as low as 6 km to as high as 20 km). There is continuous flow and swirling of air constantly through convection currents redistributing heat and moisture around the globe. This results in the short-lived and local patterns of temperature and moisture that we call weather. Because gravity holds most air molecules close to the Earth's surface, the troposphere is the densest of all layers, containing about 75% of the total mass of the atmosphere. The density of the gases in this layer decrease with height so the air becomes thinner. In response, the temperature in the troposphere also decreases with height.

Oxygen

is used by all living things to make molecules that are essential for life. It is also essential for aerobic respiration as well as combustion or burning.

Acid rain affects

lakes, streams, and forests and the plants and animals that live in these ecosystems, as well as to infrastructure. the impacts include: Acid rain causes the release of substances that are toxic to trees and other plants, such as aluminum, into the soil. Scientists hypothesize that this combination of loss of soil nutrients and increase of toxic aluminum may be one way that acid rain harms trees (Figure 5.13). Such substances also wash away in the runoff and are carried into streams, rivers, and lakes. Damage to automotive paints and other coatings. The reported damage typically occurs on horizontal surfaces and appears as irregularly shaped, permanently etched areas. Acidic particles contribute to the corrosion of metals (such as bronze) and the deterioration of paint and stone (such as marble and limestone). These effects significantly reduce the societal value of buildings, bridges, cultural objects (such as statues, monuments, and tombstones) (Figure 5.14). Sulfates and nitrates that form in the atmosphere contribute to visibility impairment, meaning we cannot see as far or as clearly through the air. Sulfate particles account for 50 to 70 percent of the visibility reduction in the eastern part of the U.S., affecting our enjoyment of national parks, such as the Shenandoah and the Great Smoky Mountains.

More industrialized countries

most dangerous is radon and cigarette smoke

Carbon info

no new carbon ever All plants, animals (including humans!), fungi, bacteria, and archaea are made of mostly carbon-based molecules such as lipids, carbohydrates, proteins, and nucleic acids.

global warming potential,

or GWP, of each greenhouse gas. The GWP of a greenhouse gas is based on its ability to absorb and scatter energy, as well as its lifetime in the atmosphere. Since CO2 is the most prevalent greenhouse gas, all other greenhouse gases are measured relative to it.

glucose molecules

organic carbon

Plants and other photosynthetic organisms are called primary producers, because they "fix" atmospheric CO2 into

organic carbon, such as sugar, a form that is usable by animals and other organisms that need to consume their carbon molecules.

Infiltration

outdoor air flows into the house through openings, joints, and cracks in walls, floors, and ceilings, and around windows and doors

criteria pollutants

particulate matter, sulfur dioxide, carbon monoxide, nitrogen oxides, ozone, lead Under the Clean Air Act (see section 5.7.1), the Environmental Protection Agency (EPA) establishes air quality standards to protect public health and the environment. Of the six pollutants, particle pollution and ground-level ozone are the most widespread health threats. EPA calls these pollutants "criteria" air pollutants because it regulates them by developing human health-based and/or environmentally-based criteria (science-based guidelines) for setting permissible levels. The set of limits based on human health is called primary standards. Another set of limits intended to prevent environmental and property damage is called secondary standards.

acid rain

ph below 5.6 -contains higher than normal amounts of nitric and sulfuric acid - comes from rain and particulates -natural and natural sources

primary pollutants

pollutants that are put directly into the air by human or natural activity. are those released directly from the source into the air in a harmful form. The primary pollutants that account for nearly all air pollution problems are carbon monoxide (58%), volatile organic compounds (VOCs, 11%), nitrogen oxides (15%), sulfur dioxides (13%), and particulate material (3%).

Air exchange rate

rate at which outdoor air replaces indoor air

Global ozone concentrations change periodically with

regular natural cycles such as changing seasons, winds, and long time scale sun variations

smog

smog is a mixture of air pollutants (sulfur dioxide, nitrogen oxides, ozone, and particulates) that often form over urban areas as a result of fossil fuel combustion. The term was coined from the terms "smoke" and "fog" referring to a brownish haze that pollutes the air, greatly reducing visibility and making it difficult for some people to breathe

hrough the flux of decomposition

some decaying biomass is converted into atmospheric carbon by the decomposers, while most of the biomass is buried into the soil, contributing to soil carbon. In oxygen-rich environments, decomposers rapidly consume dead and decaying biomass using the same process of aerobic cellular respiration described above. In oxygen-deficient environments, decomposers complete other metabolic pathways, and very slowly consume the organic matter. Some of the gases produced from anaerobic decomposition include methane (CH4), nitrous oxide (N2O), and the foul- smelling hydrogen sulfide (H2S).

indoor air pollution sources

sources such as oil, gas, kerosene, coal, wood, and tobacco products; building materials and furnishings as diverse as deteriorated, asbestos-containing insulation, wet or damp carpet, and cabinetry or furniture made of certain pressed wood products; products for household cleaning and maintenance, personal care, or hobbies; central heating and cooling systems and humidification devices. Pollutants causing indoor air pollution can also originate from outside sources such as radon, pesticides, and outdoor air pollution

atmosphere

the envelope of gases surrounding the earth or another planet.

Carbon Dioxide (CO2)

the greenhouse gas responsible for most of the human-caused climate change in our atmosphere. It has the highest concentration in the atmosphere of any of the greenhouse gases that we'll discuss here. Remember that CO2 is a direct product of both combustion and cellular respiration, causing it to be produced in great quantities both naturally and anthropogenically. Any time biomass or fossil fuels are burned, CO2 is released. Major anthropogenic sources include: electricity production from coal-fired and natural gas power plants, transportation, and industry

UV-B

the most harmful form of UV radiation that reaches the surface is UV-B. However, the UV-C does not make it to the amount of UV-B that reaches Earth's surface is significantly reduced because most of it is absorbed by ozone in the stratosphere. Ozone is the only known gas that absorbs UV-B.

Albedo

the proportion of the incident light or radiation that is reflected by a surface, typically that of a planet or moon.

Earth's atmosphere is divided into four distinct layers based on

thermal characteristics (temperature changes), chemical composition, movement, and density (Figure 5.1).

Clean dry air

unpolluted air that does not contain water vapor 78% nitrogen 21% OXYGEN 1% argon .03% carbon dioxide

Ozone depletion occurs when

when the rate at which ozone is broken down is greater than the rate of its creation, interfering with the dynamic balance between creation and destruction that maintains the ozone layer. When this happens, the amount of harmful UV-B radiation that reaches the Earth's surface increases. Ozone depletion was first identified over the Antarctic. Scientists suggested that reactions involving man-made chlorine-containing compounds were responsible for depleting ozone in the stratosphere. This hypothesis was based mostly on the physical and chemical properties of these compounds and knowledge about atmospheric conditions.

Mesosphere

which extends to about 85 km above the Earth's surface. The mesosphere has no ozone molecules and the other gases such as oxygen and nitrogen continue to become less dense with height. As a result, not much ultraviolet and x-ray radiation from the sun is absorbed by molecules in this layer so temperature decreases with altitude. Both the stratosphere and the mesosphere are considered the middle atmosphere.

Biomass

which is biological material derived from living, or recently living organisms, is a much smaller reservoir of carbon.