C3261 Final Flashcards
In any gas, molecules obey which distribution?
Maxell-Boltzmann Distribution
What is the most probable velocity?
The apex velocity, vp
What is the equation of the most probable velocity, vp?
vp=sqrt(2RT/M)
As the size of a gas molecule increases, what happens to the average velocity?
Decreases
What equation is mainly used to describe a real gas? (do not need to give the equation just the name)
Van der Waals equation
Triple point
all 3 phases are in equilibrium
Vapour Pressure
Below the boiling point, some molecules have enough E to escape the surface as a gas
At what point is the boiling point in terms of vapour P?
Boiling point when vapour P=external P
What do melting and boiling points largely depend on?
Intermolecular forces
Clathrate
A host-guest combination when molecules are trapped in interstitial spaces of an ice structure
Hydrate clathrate
A specific clathrate in which the host is ice
What happens when a clathrate-hydrate melts?
Guest is released as there is no bond between the host and guest
What is the packing arrangement of hydrate clathrates and what are the 2 types of cages in the structure?
Weaire-Phelan geometry
1. 2 cages with pentagonal faces
2. 6 cages with hexagonal faces
What do thermodynamics describe in a reaction?
If a reaction happens or not
What do kinetics describe in a reaction?
How fast the reaction will be
Gibb’s Free Energy equation
dG=dH-TdS
Order of entropy for states
s<l<g
With an increase in gas molecules, what happens to the entropy?
Increases
Photochemically-Driven Rxns
driven by photon energy during the daytime; highest E radiation in Earth’s upper atmosphere
What are the photochemical E relations? (2)
E=Nhv
N=avogadros number
h=Planck’s constant
v=frequency of EM radiation
c=lambda v
Ionization reactions
Occur in upper atmosphere and solar system
Ionization Energy
Minimum E required to ionize a molecule or atom
Electron Affinity
E required for addition of electrons to an atom or molecule
Hund’s First rule
The ground state has the greatest multiplicity, i.e. the highest number of unpaired electrons
Equation for multiplicity
2S+1 where S is the spin of unpaired electrons
Triplet state
Multiplicity 3 (2 unpaired electrons)
Singlet State
No unpaired electrons
Multiplicity 1
What are geological time scales measured in?
Millions (Ma) or billions of years (Ga)
Hadean Eon
Formation of Earth, starting 4.6 billion years ago and ending 4 billion years ago
Archean Eon
4000Ma-2500Ma. Earth’s crust cooled enough to allow formation of continents
Proterozoic Eon
2500Ma-540Ma. Transition to an oxygenated atmosphere and complex life appears near the end.
Phanerozoic Eon
541Ma-Present. Divided into periods.
Cambrian Period
540-485Ma. Before, living organisms were small, unicellular, and simple. Complex, multicellular organisms became more common. In this period, there was a rapid diversification of life in oceans.
Cambrian Explosion
Describes the diversification of life in oceans during the Cambrian period
Carboniferous Period
360-300Ma. Terrestrial life established (vast forests). High oxygen production resulted in highest atmospheric gas concentrations of all time.
Permian Period
300-250Ma. The largest mass extinction occurred here.
Permian-Triassic Extinction Event
Occurred around 250Ma. Largest mass extinction event in history, with 90% of marine and 70% of terrestrial species going extinct
Triassic Period
250-200Ma. Dinosaurs appear.
Jurassic Period
200-145Ma. Dinosaurs dominate most ecosystems
Cretaceous Period
145-60Ma. Dinosaur dominant and warm climate. A second peak in oxygen concentration occurs. Ended with another mass extinction, including all non-avian dinosaurs.
In 1896, Svante Arrhenius used principles of physical chem to estimate the extent of the increase in atmospheric carbon dioxide increases surface temperature. What is this known as?
Greenhouse effect
Around how much particulate mass of our galaxy is in space?
~10%
What is the relative particle density in space?
1-100atoms/m^3
Interstellar clouds
Have significantly higher densities
Diffuse interstellar clouds
Particles are mainly ionized atoms
Molecular interstellar clouds
High enough density for formation of a high proportion of molecules, neutral and ionized
Nebula
A concentration of gas and solid particles
Trihydrogen Ion
most common molecular ion in interstellar space
How is trihydrogen formed in space?
Dihydrogen is impacted by cosmic ray to produce an electron. The produced dihydrogen cation reacts with neutral dihydrogen to form the trihydrogen cation
What is the most common heteronuclear diatomic species in the universe?
HeH+ (hydridohelium ion)
What is the significance of Sagittarius B2 (SgrB2)?
Nearly every currently known molecule has been detected in this space
How are so many molecules formed in SgrB2?
Presence of small particulates provide surface for congregation of molecules and their surface rxns.
Atmosphere
Layer of gas surrounding a planet/moon/solid body
What makes an atmosphere more likely to be retained?
Strong gravitational field
Low atmospheric Temp
Jeans Escape Mechanism
Atmosphere leaks molecules into space. To escape, molecules need velocity in excess of the escape velocity of the gravitational fields. The proportion of high energy molecules in the tail of Boltzmann distribution determines the rate of atmospheric loss
What are the 2 important considerations in escape velocities?
Atmospheric temperature
Gravitational field
Solar Wind
the sun expels streams of ions from upper layers, consistent of electrons, protons, and alpha-particles.
How does solar wind impact atmospheres?
Solar wind exerts a small P where it impacts a solid body, which can erode the atmosphere
Magnetosphere
Planets with large magnetic fields have a region that allows solar wind to be deflected. This is an important factor in the retention of an atmosphere
What are the 4 gas giants
- Jupiter
- Saturn
- Uranus
- Neptune
Which of the gas giants have the greatest complexity in chemistry?
Jupiter
Great Red Spot
Vortex first observed in 1665 on Jupiter
Oval BA
Red sport formed by the combination of 3 smaller white spots in the year 2000 on Jupiter
Describe the vertical structure of Jupiter’s atmosphere
No simple transition from atmosphere to solid surface (on all gas giants). Because of low T and extreme P, there are ill-defined boundaries into supercritical hydrogen and helium.
3 Major cloud layers on Jupiter
- H2O
- NH4HS
- NH3
Where do the colors of Jovian clouds arise?
From organic species. Photodissociation of methane under high E UV reaching upper stratosphere produces many radical species that can further react to many organic compounds
What are the 3 inner rocky planets (omit earth)?
- Mercury
- Mars
- Venus
Why is mercury not important in the atmospheric chemistry discussion?
The low mass, combined with location in relation to sun and strong solar winds, and low magnetic fields, means that mercury has essentially no atmosphere.
Describe some of the conditions of Mars
Surface P around 6kPa
CO2 dominates the atmosphere
Surface T below freezing point of water
CO2 exists as solid near the poles
What has been used to establish the loss of the Martian atmosphere?
Isotopic analysis of Ar-36/38
What proportion of the Martian atmosphere is expected to have been lost?
2/3
What are the major components of the Venus atmosphere (2)?
- CO2
- N2
Why is Venus termed “Earth’s twin”?
Similarities in structure, the two planets were likely similar a long time ago
What causes the extreme temperatures on Venus?
Result of extreme radiation trapping. The surface T is around 470C, above the melting point of many metals including Pb, Sn, and Zn
As water evaporated on Venus surface, the radiation trapping ability of water led to what concept?
Runaway greenhouse effect
What different types of cloud layers exist on Venus?
Sulfuric acid
Fe2Cl6 and Al2Cl6 dimers have been identified in upper/lower clouds
What is the most common trace species on Venus?
SO2
What material exists as SCF on Venus?
CO2
Rotational E
E due to rotation of atoms or molecules. Very small separations in E levels.
Vibrational Energy
Only for molecules. Atoms within molecules are in constant vibration.
Electronic Energy
Transition of electrons in atom or molecule requires substantial E. Transition is photon in UV or vis region. Each electronic level has multiple vibrational levels.
Fundamental Vibration
Excited when one E is absorbed by molecule in its ground vibrational state
Gross Selection Rule
for IR absorption, the dipole must change. No need 4 permenant dipole, but must be a change.
Which type of molecules do not absorb IR/do not contribute to radiation trapping?
Diatomics
Types of vibrations (3)
- Symmetric stretch
- Antisymmetric stretch
- Bend
What type of vibration does not absorb in linear molecules?
Symmetric stretch
Zero Point Level
Lowest vibrational state
Bond Dissociation Energy
E required 4 bond fission
3-body collision
One component takes away excess vibrational E, becoming excited, and the other 2 react.
What are the 7 considerations in MO Theory?
- Mixing 2 atomic orbitals of same or similar E results in 2 MOS, bonding and antibonding.
- Bonding orbital E < antibonding E
- Each MO holds 2 electrons
- Lowest E orbitals fill first
- Hund’s Rule: parallel spins first
- Bond Order= bonding pairs - antibonding pairs
- Labelling (sigma and pi)
Frank-Condon Principle
No change in inter-nuclear distance during electronic transition, i.e. a molecule is frozen in its vibration
Radiationless Decay
Once in excited electronic state, molecule loses small amount of E, dropping 2 lowest vibration level.
Fluorescence
Loss of E as light as electron drops from excited electronic state to ground state
Intersystem crossing
Electron excited 2 upper singlet E state undergoes crossing which involves spin flipping
Phosphorescence
The spin reversal during intersystem crossing takes time; the delay in releasing light is known as phosphorescence
Jablonski Diagrams
Shows energy and wavelength of different E states
Spin Conservation Theory
In the products of rxn, both must be spin triplets or singlets
What are the Galactic Parameters
- Star has to be of an intermediate size
- Lifetime of a star is inversely proportional to its mass
- Location in galaxy
Tidal-Lock
When small starts have long lifetimes, their luminosity is low; the planet would have to orbit close to star. Gravitational attraction locks 1 face of the planet to face the star; cold side and hot side
Describe the galactic parameter based on location in galaxy
Explosion of large stars gives intense radiation; planets around stars near center of galaxy are more likely to be exposed to periodic radiation outbursts. Location on periphery of galaxy is much safer
Describe the time constraint on galactic parameters
Star and surrounding gas/dust envelope must have formed late in the evolution of the universe that some of the first stars exploded, scattering elements.
Current atmospheric composition on Earth
Around 78% N2, 21% O2, 1% Ar and other trace gases
Origin of Atmospheric Gases
Early earth was bombarded with ice comets; these may have been N2 and/or CO2 ice clathrates, releasing these gases as they melted
Rock vapour atmosphere
Another body impacted pre-Earth (before formation), smashing off moon, resulting in high T and creating a rock vapour atmosphere, which condensed within 2000 years.
What were the characteristics of the second original atmosphere?
Dense mixture of water vapour, CO2, and other gases. T cooled and liquid water formed, around 2Ma. The temperature and pressure conditions solubilized mineral ions faster than today. Mineral beds formed as the seas cooled and carbonates precipitated.
Faint Young Sun Hypothesis
As a star ages, the core contracts and rate of nucleosynthesis increases, i.e. luminosity increases with age.
In early times, high levels of RTGs; as the sun brightened, decreasing concentration of RTGs resulted in balancing of T on earth and came within a life supporting range.
What is Titan the moon of?
Saturn
List some characteristics of Titan
Planet-like moon
Larger than Mercury
Only non-planet to have an atmosphere
Humans could fly because of low gravity
Nitrogen rich atmosphere
What is a theory based on the formation of Titan?
Titan was once a planetoid captured by Saturn’s gravitational field. Titan’s atmosphere may be a model for early Earth
How is it theorized that Titan picked up N2 in its atmosphere?
Titan picked up N2 atmosphere by N2 clathrates from the Opik-Oort
Opik-Oort Cloud
Big belt of icy planetesimals far outside the solar system
Atmospheric Structure of Titan
Titan is very different to other atmospheres. Between 20-40km, CH4 clouds with N2 droplets. Ethane fog close to surface. Tholin haze at higher altitudes.
What are the main reactions that occur in Titan’s atmosphere? (2)
- Methane reactions
- Nitrogen reactions
Tholins
Atmosphere of Titan is orange because of wavelengths absorbed by a haze of tholinds, a liquid/solid mixture of highly unsaturated compounds with C/N/H.
What happens when tholins are warmed to room temp and water is added?
They hydrolyze to give amino acids and other building blocks of life.
Theory of life on Earth related to tholins
Life on earth started from impacts of tholin-comets into warm seas of early Earth
Inorganic Carbon Cycle
Helped early CO2 disappear; much slower and less prominent today
What did the weathering process do to silicates over millions of years?
Eroded silicate mountains
REVIEW INORGANIC CARBON CYCLE
What type of feedback cycle is weathering?
Negative feedback
Increasing T = weathering faster than volcanic output = lower atm CO2 = lower radiation trapping = planetary cooling
What do volcanic eruptions return to the atmosphere in the ICC?
CO2
What were the first living organisms
Anaerobic bacteria
Metamorphic Rock
Minerals deep in earth with high compression and heat changed to new compounds. Organic compounds cannot survive, but, graphite bands are seen in rocks, which are enriched in C-12. Rate of deposit suggests it comes from biochemical processes
Stage 1
3580Ma-2450Ma. First fossil evidence of organisms found from deposits of Dresser Formation; cyanobacteria
Stromatolites
Mats formed cylindrical aggregates. Surviving locations are in extreme environments
Thrombolites
Mats with lumps rather than layers. One of only 2 sites is in NL.
Stage 2
2450Ma-1850Ma. Atmospheric O2 increased and partial P of O2 increased
Great Oxidation Event
Shallow seas were partially oxygenated by photosynthesis; deep oceans remained anoxic
Oxygen Catastrophe
Organisms which fluorished under anaerobic conditions were exterminated by O2 rise
What shift occured in the oceans as O2 in the atmosphere increased?
Went from primarily reducing to strongly oxidizing
Lomagundi Carbon Isotope Excursion
Sudden change in C isotope ration to highly positive. No explanation, although there was a sudden decrease in atmospheric O2 around this time
Stage 3
1850Ma-850Ma. O2 recovered and stabilized
Boring Billion Years
Called this due to atmospheric stability, however, it was a period of great biological change
Euxinic
Anoxic and sulfidic (rich in H2S)
Canfield Ocean Model
Surface layers became O2 rich where lower parts remained O2 free
Stage 4
850-540Ma. Deep oceans became oxic. Complex organisms. Trilobites.
Stage 5
540-0Ma. O2 rich. Ozone layer in upper atmosphere. Once this formed, life spread to land and plants produced O2.
End Permian Event (Great Dying)
96% of marine and 70% of terrestrial vertebrates went extinct. Insects died which are typically unaffected by extinction events. CO2 raised by 2000ppm
Cretaceous-Paleogene Extinction Event
around 66Ma. Resulted in end of 3/4 of the planets animal species, including all nonavian dinosaurs. Strong evidence this was a result of a major meteorite impact
Pseudo-First Order
Concentration of 1 reactant is much less than others
Elementary rxn
Single step
Rate determining step
Rate can be no faster than the slowest step
Intermediate
Species formed then consumed
Steady-state hypothesis
The concentration of all intermediates remains constant
Parallel Reactions
A reactant can react by 2 or more different pathways
Chain Reaction
Products of 1 reaction step further undergo reaction and generate a cycle
What are the steps in a chain reaction? (4)
- Initiation step
- Propagation steps
- Inhibition step
- Termination step
Chain length
Number of propagation steps
Chain carriers
Reactive species which result in a chain reaction
Branched chain reactions
Normal chain reactions, consumption of 1 chain carrier leads to birth of another. Only differences is the branched step after propagation steps.
What does simple collision theory involve? (3)
- Molecules are hard, structureless spheres
- No interaction occurs until molecules collide
- All collisions lead to a reaction
For what 5 reasons was simple collision theory discredited?
- Rates slower than predicted
- Rates accelerate faster with higher T
- SCT ignores molecular shape and orientation
- Reactions happen over finite time, not instantly
- Long range interactions exist as molecules approach
Transition state theory
Provides explanations for each point which was a weakness in simple collision theory.
Transition state
Exists at max reaction E and cannot be isolated; essentially the opposite of an intermediate
Free E of rxn
thermofeasibility of reaction
Free E of Activation
E necessary to reach the transition state
Substrates
rxns on solid surfaces
3 types of surface rxns and brief explanation
- Physisorption: attraction between molecule/substrate is based on IM forces
- Chemisorption: attraction between molecule/substrate is by covalent bond formation
- Dissociative Chemisorption: when the above is accompanied by dissociation
What are the 2 main laws of photochemistry?
- Grotthaus-Draper Law (Principle of Photochemical Activation)
- Stark-Einstein Law (Principle Quantum Activation)
Quantum Yield
Number of molecules of a reactant consumed/product formed epr quantum of light absorbed
What are the 5 layers of Earth’s atmosphere and their altitudes?
- Troposphere; 0-12km
- Stratosphere; 12-50km
- Mesosphere; 50-80km
- Thermosphere; 80-800km
- Exosphere; 800-10000km
In what atmospheric layer contains 80% of atmospheric mass, and also T decreases with altitude?
Troposphere
Tropopause
Boundary between troposphere and stratosphere
Which layer is known as the ozone-rich layer, which has increasing T with increasing altitude?
Stratosphere
Why does T decreased with altitude in the mesosphere?
Cooling is a result of CO2 emission partly. Molecules absorb E from collisions with other molecules, then radiate into space with emission from vibration excited states. Increasing CO2 contributes to mesosphere cooling.
What is the final identifiable layer in the atmosphere known as, with T increasing with altitude due to low density?
Thermosphere
What layer of the atmosphere merges with solar wind?
Exosphere
Hydrostatic Equation
Determines the P at a given altitude
Mean Free Path
Average distance a molecule can travel between collisions
Fluid Mixing
Air currents swirling molecules in bulk
Homosphere
Composition of atmosphere is constant. Part of troposphere, stratosphere, and mesosphere
Heterosphere
Atmosphere composition changes with altitude
Turbopause
Transition zone between homosphere and heterosphere
Summarize the T variation with Altitude
air cools through Trop, warms thru Strat, cools through Meso and warms through Thermo
What is the temperature profile of the atmosphere a result of?
Adiabatic expansion
Describe the process of adiabatic expansion
EM radiation from sun heats surface which emits IR absorbed by gases. Molecules in warmed air have higher molecular velocities. Less dense warm air rises and convection occurs. As it rises, the surrounding pressure decreases and the package of air expands. KE is lost to overcome IM forces and expand, thus cooling the package
Lapse Rate
Rate at which atmospheric T changes with altitude
Cloud Condensation Nuclei
A molecule requires this type of nucleus in order to condense into droplets; defined by the critical radius
Surface Energy of a droplet
always positive, so evaporation is favored. Inside the droplet, each molecule is pulled in every direction by hydrogen bonds. Molecules at surface are pulled inwards, creating an inward P, against work must be exerted to allow expansion
Critical Radius and Droplet Formation
Droplet formation can only happen if it already exceeds ro in size.
Cumulonimbus
dense, towering vertical cloud, formed from water vapour carried by upward air currents
Cumulonimbus Incus clouds
a sub-category of cumulonimbus, aka anvil clouds, which stretch close to the tropopause
Equilibrium level
Air currents spread out to give the flat top in incus clouds that is used to approximate the tropopause
Convective overshoot
If vertical velocity of air current is high enough, can penetrate into lower stratosphere; causes turbulence during flights
Polar stratospheric clouds
In extreme cold, clouds of HNO3 and H2SO4 may form in altitudes from 15-25km
What are the 3 types of polar stratospheric clouds and what are they made of?
- Type 1a: large, aspherical particles of HNO33H2O
- Type 1b: small, spherical particles of liquid supercooled solution of H2SO4, HNO3, and H2O
- Type 2: H2O(s) only; rarely observed, and only in the Arctic
Noctilucent clouds
Occur in the mesosphere at altitudes of 76-85km. Poorly understood
When are noctilucent clouds observed and at what latitudes/temperatures?
Summer at latitudes between 50 and 65 degrees; T < 120C
What are noctilucent clouds made of?
Tiny ice particles smaller than 100nm in diameter.
Rayleigh scattering
Molecular interactions with visible solar radiation. Particles are much smaller than the wavelength of incident radiation
What does Rayleigh scattering explain?
Blue color of the sky
Mie Scattering
Particles are of same range of size as wavelength of light
Geometric scattering
Particles are much larger than wavelength of light
Which type of scattering describes why clouds are colored white?
Geometric scattering
Wien’s Law
Wavelength of greatest emission from a body is inversely proportional to the T
IR absorptions
Absorption of RTG keeps T of Earth within habitable limits
Energy balance
E that affects climate is radiant E from sun. Planet and atmosphere absorb radiation and reflect some back to space. The difference between the absorbed and reflected E determines the average global T.
Radiation Forcing
More RTGS = Lower E radiated back to space. Measure of the influence a factor has in altering the energy balance
What is tropospheric ozone?
Urban pollution
Dobson Unit
Total vertical concentration of ozone. Thickness of layer of purge gas formed by “squishing down” the total column amount
Chapman Mechanism
Describes the formation of ozone
Who found evidence of OH radical and NO could catalyze the mechanism and speed up the destruction of ozone?
Bates and Nicolet
Null cycle
Same number of odd species as both reactants and products
Holding cycles
Equilibria involving 2 catalytic species which combine to form a stable species, known as a reservoir species
What compounds were used as refigerants that were problematic?
Chlorofluorocarbons
What was the unintended consequence of replacing NH3 with fluorocarbons in refigerants?
Fluorocarbons have no decomposition mechanism in the troposphere, so they remain forever. As they diffuse, some pass into the stratosphere and provide a source of Cl for ozone destruction
Ozone Depletion Potential
Ratio of global loss of ozone due to the compound compared to global loss ozone due to CFC-11
What are the 2 contributions to ODP?
- Number of Cl or Br atoms per molecule
- Atmospheric Lifetime: measure of time required to restore original equilibrium following a sudden increase or decrease in the species concentration
Hydrofluoroolefins
Have lower ODP but higher greenhouse gas potential, due to shorter atmospheric lifetimes
What are the 2 main sources of stratospheric bromine?
Methyl bromide and Halon 1211 (CBrClF2)
Describe methyl bromide
Colorless, odorless, nonflammable, produced industrially and biologically. Soluble in H2O. Included in Montreal Protocol. Produced by marine organisms and some terrestrial families. Used as pesticides/sterilizing agents/insecticides/rodent repellants. Can kill humans
Describe Halon 1211
Dense, nonflammable, nontoxic, banned under Montreal protocol but still widely used as fire control in computer rooms (and has some military applications)
Which part of the world faced the most loss of ozone?
Antarctic
Ozone hole
Depression of ozone
Extreme polar ozone depletion
Better term for ozone hole
Antarctic Polar Vortex
rotation of wind isolates Antarctic atmosphere. In winter, no sun=no thermal E input and the atmosphere cools drastically. Odd N species produced. In the spring, photochemical reactions are driven.
Montreal Protocol on substances that deplete ozone layer
International treaty designed to protect ozone layer by phasing out substances that deplete ozone. 8 Revision by adding molecules. Since then, decrease in atmospheric concentration of ozone destroying compounds and [O3] has stabilized, however the Antarctice O3 hole will continue for decades.
Detergent Molecules
Hydroxyl radical which affects daytime chemistry and nitrate radical dominates night-time chemistry
What are detergent molecules also known as?
Scavenger species
What is the major source of hydroxyl radical?
Photolysis of ozone
Quenched
Lose excitation E
Why does the nitrate radical only exist at night?
The nitrate radical reacts with photons to break into compounds and is destroyed with sunlight
Nitrogenase
Enables some micro-organisms to reduce N2 to NH4+ (Fe-Mo core acts as a reduction center)
How is Ar-40 in our atmosphere formed?
From the radioactive decay of K-40 in potassium minerals
Global Warming Potential
Compares quantity of heat trapped by a certain mass of a gas to an equal mass of CO2; i.e. GWP CO2 = 1.
What are the 3 factors that GWP depends on?
- Intensity and number of IR absorptions
- Spectral location of absorptions
- Mean atmospheric lifetime
The Azolla Event
Happened in the middle Eocene epoch around 49Ma. Prior, Earth was a greenhouse planet and the poles were very warm. High CO2. Surface layers of Arctic ocean were warm/freshwater (landlocked). Azolla died in large amounts and sinked over time. The anoxic organic remains sequestered C content into seabed, halving atmospheric CO2 and decreased global T substantially
Juvenile CO2
CO2 freshly released from volcanic activity
Recycled CO2
Due to plant respiration, forest fires, anthropogenic oxidation of fossil fuels
What processes form CO2 and CO?
Complete combustion = CO2
Incomplete combustion = CO
Keeling Curve
Ongoing plot of concentration of CO2 based on year. Measurements made at an observatory in Hawaii
Sources of methane
Anaerobic bacterial action on organic matter. Leaks in natural gas pipelines. Very large underground deposis of methane
Methane clathrates
Common in shallow marine geosphere, deep sedimentary formations can form outcrops on the ocean floor. Type 1 structure. Density around 0.9g/mL, will rise to surface and melt, releasing bubbles. Formed when methane gas under seafloor travels upwards through cracks in rock formations. As it travels through cold water, the water molecules solidify around each methane molecules.
Water Vapour Feedback
As global mean T increases, saturation water P increases exponentially; atmosphere can hold more water
What are the natural sources of sulfur dioxide? (4)
Volcanoes
Coal combustion
Oil combustion
Production of metals from sulfide ores
London Smogs
Used coal for home heating, cheap coal with high S. Upon combustion, CO2, hydrocarbons, and SO2 were released. Cold atmosphere conditions prevented dispersal of pollutants
Which oxide of N is not colorless?
NO2
Photochemical (LA) Smog
Result of reaction between hydrocarbons and NO with UV/blue solar radiation as an E source. Typically the NO source is internal combustion engines
What is a significant contribution in photochemical smog?
PAN (peroxyacetyl nitrate)
PAN is dangerous because it is potent in 2 factors, which are:
1: Lacrymator: causes eye irritation
2: Phytotoxic: causes yellowing of plant leaves
Super Greenhouse Gases
Strong IR absorptions in regions transparent to current absorbing gases. Long atmospheric lifetimes. GWP in 10s of thousands.
What are the 4 major super greenhouse gases (fluorine species)?
- NF3
- SF6
- Trifluoromethylsulfur pentafluoride
- TFA
Describe NF3.
Large vacuum chambers required for manufacture of silicon circuitry. NF3 was used as this.
Atmospheric lifetime over 500 years.
GWP around 17000
Describe SF6
Used for arcing (electrical discharges leap across the air gas, and must be inhibited)
Dense, non toxic
Atmospheric lifetime at least 3200 years.
GWP=23900
Radiation trapping equivalent to a billion tonnes of CO2
Describe TFA
Highly water soluble, rained out and enters lakes/rivers. Was replaced as refigerants.
Intergovernmental Panel on Climate Change (IPCC)
provide data for discussion on RTGs. Reports issued in different years, covering scientific, technical, and socio-economic info relevant to understand scientific basis of risk of buman-induced climate change, impacts, and mitigation.
Kyoto Protocol
International agreement signed in Kyoto 1997 and implemented in 2005. Based on principle that it was the responsibility of all states to reduce their emissions of RTGs.
Doha Amendment
An amendment of the Kyoto protocol which many countries agreed to. Focussed on CO2, CH4, and N2O. Others were added later.
Paris Climate Accord
Separate agreement negotiated by UN panel on climate change. Aimed at reducing RTGs worldwide, setting global T rise limit to 2C.
No legal enforcement
Principle of Progression
After every 5 years, new target should be more ambitious than the last for climate accord
Non-Methane Hydrocarbon sources
Many plants. Result in haze over many forested mountains known as Blue Mountains
Isoprene
Most important natural NMH. Synthesized and emitted by many species of trees. accounts for about 1/3 of all HCs released
Thermal Protection hypothesis
high-producing isoprene plants are heat tolerant. In biochemical pathways, isoprene may be a scavenger for hydroxyl radicals and acts as an antioxidant in cells.
Kudzu
Plant that is a high isoprene producer.
Monoterpenes
Class of HCs with conjoined isoprene units. Widely generated in temperate forests.
Criegee intermediate
Formed by ozone oxidation of monoterpenes. Has a high lifetime
Describe DMS (dimethyl sulfide)
-Source of biogenic sulfur
-One of 2 decomposition products of metabolite DMSP
-Produced by phytoplankton and seaweeds
Is the polarity of DMS and chloromethane low or high? (and what does this mean)
Low polarity.
Easy escape to atmosphere
What compound is responsible for forming an equatorial ring of atomic iodide, that maximizes mid-day?
Iodomethane
Global distillation, definition
transport of pollutants from lower to higher latitudes
Another name for global distillation
Grasshopper effect
How was the process of global distillation discovered?
Pesticides and other toxic chemicals were found in Arctic through bioaccumulation.
Describe the global distillation process.
Volatile chemicals are warmed and travel to cooler locations in the gas phase, where they condense back to a liquid. The net effect is atmospheric transport from low to high latitudes. This is a slow process and is only effective for chemicals of measurable volatility that do not readily decompose.
Persistent Organic Pollutants (POPs)
Participate in global distillation.
Measurable volatility that are not readily decomposed.
Chemical substances that persist in the environment, bioaccumulate, and pose risk of causing adverse impacts to human health and the environment
Stockholm Convention on POPs
International treaty signed in 2001 (effective 2004) that aims to eliminate/restrict production and use of POPs.
What 3 groups of POPs (9 compounds) make up the dirty dozen?
Dioxins, furans, and PCBs (polychlorobiphenyls)
PFOS
Perfluorooctanesulfonic acid
Long-chained perfluoro compounds, used as water repellent (stain-proofing fabrics) and has no decomposition pathways (persists forever). Highly toxic and accumulates.
Mercury species emission
65% coal burning in US and China
10% gold-extraction process
Describe characteristics of mercury species
High vapour pressure, undergoes global distillation easily. Some bacteria can convert HgBr2 to highly-toxic methyl mercury chloride, which accumulates
Arctic Haze
Aerosol of about 90% S and C. Formed due to coal-burning in the south. Reduces visibility to 1/10th of the normal. Occurs in winter and spring.
Global Dimming
Has a negative effect on radiation forcing. Shows some particulates cause reduction in solar intensity reaching earth. Reduces global Ts.
Aircraft contrails
Vapor trails of aircrafts; often emit CO2, NOxs, SO2, and H2O gases which contribute to radiation forcing. However, the vapour trails from aircrafts (contrails) are implicated in global dimming due to combination of low T/high altitude which creates ice-crystal trails.
How was the contrail effect tested?
After 9/11, there was an increase in daily max T of over 1C due to no flights for 3 days.
Ship tracks
Emissions from ships at sea that produce vapour trails
Aerosol
Combination of suspended particulates in air
Atmospheric Aerosols
Particles are called atmospheric particulate matter, and are graded by diameter. Can penetrate deep into lungs and enter the bloodstream. Bacteria and microorganisms can stick to PM and can infect those who inhale
Air Quality Index
reports the levels of PM for each country.
Atmospheric boundary layer (ABL)
Lowest part of troposphere where most particulate pollution originates and stays. Rapid fluctuations in flow velocity, T, and humidity; vertical mixing is strong. Pollutants become trapped in ABL due to low air flow because of aerodynamic drag
Free Atmosphere
Above ABL; non-turbulent
China Smogs
Predominantly particulate. Many industrialized cities have these.
Natural Particulates
From volcanic eruptions: can cause major short-term climate differences.
Deserts: specifically the Sahara, where between 60 and 200 million tonnes of mineral dust are lifted by convection; can reach all the way to caribbean/florida. Can kill coral polyps.
Asian Dust
Aerosols carried east and can make it to western US. Smaller dust clouds that are produced in Asia, in the Gobi Desert (Mongolia and China)
Sea Spray
Water evaporites from turbulent seas, containing many mienrals (NaCl, Mg, Ca, etc.)
Southeast Asian Haze
Due to illegal clearing of forests in Indonesia
How are gray glaciers in Greenland formed?
Elemental C particulates are conveyed over Greenland. They deposit on white glaciers and increase absorption of solar radiation, leading to increase in melting and gray color.
Particulate deposition
Aerosols deposit on solid surfaces
Wet deposition
Particles absorbed upon ice crystals or into rain drops. Aka scavenging
Dry deposition (2 types)
Depends on particle size.
1. Sedimentation: large particles, a result of gravity.
2. Coagulation: small particles; impacts between particles caused by Brownian motion
What happens to intermediate sized particles in terms of particulate deposition?
Dry deposition rate for intermediate size particles is really slow, as they are highly persistant. This range is known as the Greenfield gap.
Homosphere characteristics
Short mean free path
Low altitude
Eddy diffusion causes consistent composition
Heterosphere composition
High altitudes, longer mean free path, composition becomes differentiated
Mesosphere/Lower Thermosphere Region (MLT)
Stratosphere to just above the turbopause (70-110km). Consider as a single unit.
What atom is essential to upper atmospheric chemistry?
Atomic O
Meteroids
Solid debris from space.
Meteroite
Meteoroid that reaches earth
Stongy meteorides
From crust fragments; silicate minerals
Iron meteorides
metallic iron with some nickel.
At what speeds do meteors impact the atmosphere (above)
40km/s
What happens when meteors impact the atmosphere?
Massive friction in mesosphere; the heat ablates surface or all of the object into gas phase, providing a source of Na, K, Mg, Ca, Fe, and Si.
Harpoon Mechanism
Describes how Na is oxidized to NaO in the atmosphere.
Long-range electron transfer is followed by reduction of distance between donot and acceptor.
Airglow
Atomic O and Na emissions in visible region produce this.
Dayglow
Results from impact of solar radiation; more intense in the daytime.
What form of airglow is weaker but still possible to observe?
Nightglow
Which form of airglow is the most possible to observe?
Twilight glow
What auroral lines fo emissions from atomic O produce?
Auroral green line
How are auroral red lines produced?
They are characteristic of an emission of excited atomic oxygen to the ground state. (Green lines are from an upper excited state to a lower excited state).
IR Atmospheric Band
Of much lower Energe that the visible range
What color do Na emissions produce?
Yellow
Aurora
Sporadic, resulting from interaction of high velocity/E solar charged particles following Earth’s magnetic lines of force and impacting high altitude species.
Where do aurora occur?
Auroral Zone
Arctic aurora
Aurora borealis
Antarctic aurora
Aurora australis
What is the most common color in the aurora, and what other colors are possible?
Green
Blue,red
Ionosphere
Region of ions high in the atmosphere
Ionized by solar radiation.
Defined in concentration of ions.
Also includes the highest concentration of free electrons
How does the ionosphere differ between daytime and nighttime?
In the day, the ionosphere is 50-1000km (Meso, Thermo, Exo). However, during the night, ionization in the Meso does not occur. Thus, the range of the ionosphere differs greatly with changes in solar activity
What is responsible for the reflection of radiowaves/ability of radio signals to reflect beyond horizon?
Free electrons
What are the 3 ion layers in the ionosphere?
- D
- E
- F
What ion layers are persistant at night?
F, D is weakly
What ion layers are strongest during the day?
D and E are heavily ionized, F develops a weaker region known as F1, and F2 persists at day and night.
F Region
150km-300km. Electron denser; high exposure to EM radiation
E Region
90-150km
D Region
60km-90km
