Atmosphere: Composition and Gases

Atmosphere Basics

• The atmosphere is a layer of gases held in place by Earth's gravity
• Top four gases constitute 99.998% of its volume
• This is based on clean, dry air without water vapor

Permanent Atmospheric Gases

• Nitrogen (N2) comprises 78.08% of the atmosphere
• Nitrogen dilutes oxygen, preventing rapid burning
• It is also used by living organisms to produce proteins
• Oxygen (O2) accounts for 20.95% of the atmosphere
• Oxygen is used by living things to make essential molecules
• It is needed for aerobic respiration and combustion
• Argon (Ar) constitutes 0.93% of the atmosphere
• Argon is a non-reactive gas used in light bulbs and double-pane windows
• It also preserves documents like the Declaration of Independence and the Constitution
• Hydrogen (H2), Helium (He), Neon (Ne), and Xenon (Xe) are also present

Variable Atmospheric Gases

• Carbon dioxide is essential for plants to make food through photosynthesis
• It acts as a blanket to trap heat, and it releases oxygen back into the atmosphere
• Water vapor's presence goes up to 4% of the volume, location-dependent
• Water vapor volume is near zero in Earth's desert regions with dry winds
• Methane (CH4), nitrous oxide (N2O), and ozone (O3) exist

Thermal Layers

• Weather refers to short-lived patterns of temperature and moisture
• The Troposphere is the densest layer, where weather happens which decreases with height
• It is the lowest layer of the atmosphere that goes up to 18 km from Earth which varies between 6 km and 20 km
• Weather formation happens and influences weather patterns due to solar radiation and air/water properties that redistribute globally
• Air movements create short-lived weather patterns
• The Troposphere contains 75% of the atmospheres total mass
• Air thins up with the altitude, and temperature decreases with height
• Averages 17°C (62°F) at sea level, dropping to -51°C (-60°F) at the tropopause

Stratosphere

• Tropopause is a boundary that limits mixing with upper layers and absorbs/scatters the sun's UV radiation, thus protecting living things
• It goes up to 50-53 km from the tropopause from Earth
• Gas amounts are similar to the troposphere
• It has almost no water vapor, but 1,000 times more ozone (O3) than the troposphere

Mesosphere

• The stratosphere contains 19% of the the atmosphere's total mass, meaning it is less dense
• Increasing temperature occurs with height and rises from -51°C (-60°F) at the tropopause to -15°C (5°F)
• This prevents convection, but allowing pollutants to remain suspended for years and marks the top of the stratosphere
• It goes up to 50-85 km of it top from Earth
• Little ultraviolet (UV) and X-ray radiation is absorbed, thus temperature decreases with height
• Alongside the the stratosphere, it is part of the middle of the atmosphere

Thermosphere

• It goes up to 600 km, and it is surrounded by the exosphere
• Gases absorb high-energy UV/x-ray radiation from the sun
• Increasing Temperature occurs with altitude, reaching 2,000°C (3,600°F) depending on solar activity
• The atmosphere ends with no sharp boundary, and density decreases and merges with the vacuum of outer space

Ozone

• Ozone (O3) has three oxygen atoms and is unstable
• The air we breathe (O2) has two oxygen atoms, is dense, and is stable
• Ozone is a pollutant on the ground level and protects life in the stratosphere

Ozone Formation

• High-energy ultraviolet (UV) solar radiation splits O2 into O
• Free oxygen atoms (O) meet with oxygen, thus forming ozone (O3)

Ozone Breakdown

• Ozone absorbs UV radiation, thus breaking down into oxygen (O2) and single oxygen (O)
• This is ongoing, and remains stable if the rate of creation is equal to the rate of destruction

Ozone Layer

• Small atmospheric gases are concentrated between 17-30km of the stratosphere
• Acts as a protective shield by absorbing UV radiation

UV Radiation Forms

• UV-A, the least harmful light reaches to Earths surface that causes sunburn and damages skin. Cannot be ozone absorbed
• UV-B is harmful and absorbed in the ozone, and if the levels drop causes health risks
• UV-C is the harmful but very high energy and is absorbed into the stratosphere
• UV-C regenerates oxygen atoms and releases heat when absorbed

Ozone Creation and Depletion Under Natural Conditions

• There is a balanced creation and destruction that creates depletion
• Ozone is declining, which leads to UV radiation increases

The Ozone Hole

• Ozone is thinning annually during October over the Antarctic
• Antarctic air is isolated, which causes temperatures to drop low in the months of darkness
• Spring sun causes UV light releases from chlorine atoms in October
• This results in lack of mixing, and breaks down and traps the zone
• This was first identified in 1985 by scientists linking it to compounds from man

Ozone Concentration Measurements

• Vary with seasons/climate
• Ground measurements since the 1920
• Satellites have been in use since the 1970's

Chlorofluorocarbons (CFCs) affect ozone

• CFCs are synthetic
• They block O3 formulation
• Stable gas rises, and does not react, so it slowly damages the stratosphere and forms chlorine
• The Cl steals one oxygen from O3 to form ClO and O2
• The ClO reacts and destroyed additional zones

Results of ozone depletion

• High UV levels
• Higher likelihood of skin cancer
• Higher likelihood of ecological harm and cataracts

The Montreal Protoco

• Signed by 198 nations by 1989, banning various ozone-depleting chemicals like Chlorofluorocarbons (CFC's) and Carbon tetrachloride (CCl4)
• HFC's are a replacement that are chlorine and ozone depleting free
• This all reduces the production by 50% in 1998
• As a result most countries stopped making harmful chemicals
• The U.S. ammends the air act, to have the EPA stop production, recycle agents and label harmful substances

Outdoor Air Quality

• Defined as the air, that is clean of harmful particles of different kinds.
• This clean quality stems from natural means, but mostly biomass burning from activities
• For instance the the U.S. is cleaner, while high smog countries are not

Pollution Is From two kinds of Sources

• Stationary that are fixed (power plants), or Mobile that move and emit (trains ships)
• Most is from emissions broken into to primary (CO) and secondary (ozone)

Air Quality and EPA Measurements

• The EPA sets clean air standards Common types:
• CO, which is from car emissions that reduce oxygen and lead to death
• O3 is a sweet odorless gas from facilities and exhaust,
• NO2 is yellow foul gas that leads to smog and acid
• SO2 comes from metal and fossil fuels that leads to acid
• Lead are particles that affect health, that has fallen due to EPA regulations
• PM, particulate air pollution from dust and burning, that have negative effects

Other Pollutant Types Include

• VOC, Carbon compounds that have indoor effects
• Smog is a type of pollution, and causes further chemical reactions such as sunlight pollution and acid rain that also harms water

Toxic Pollutants

• Toxic pollution can also lead to health and environmental issues
• Sources of pollution are man and naturally made
• Health is affect by air and water and lead to issues in both humans and animals and affect food chains

Indoor Air Quality

• Is higher in developing and developed air quality than out in fresh, outdoor air:
• Inadequate air, materials, and burning are primary factors
• The air is affected by how air flows, temperature, and pollutants
• Solutions are using renewable sources

Other Details For Indoor Air Quality Is

• Use cleaning/HVAC supplies
• Pollution is based on radiation leaks that cause cancer
• Pollution also depends on release volume, and is worse in less industrialized area because more cheap fuels are needed

Air Pollution's Affect On Our Health

• Lead has health consequences
• International orgs agree this is a threat
• Illnesses are triggered by: Asthma, and breathing in toxins
• Health risks are: old age, preexisting breathing and higher sensitivity

Acid Rain

• pH lower than 5.6 means there is acid and causes: decay due to natural causes and fossil duels with power plants
• Acid is created in natural means that spread in winds
• Issues are that the environment is altered: bad nutrients, toxic, bad water
• Infrastructure corrosion and automobile damage
• Poor visibility

Legislation

• Major events of air pollution have been understood
• Federal is better
• State local work with companies, but agencies set authority

Clean Air Results

• 40 + years lead to results while boosting U.S. economy
• emissions decreased
• quality and pollutants improved everywhere