Atmospheric Chemistry Extracted

1970 air quality standards for five(later six) air pollutants

1. PM - Suspended particles/particulate matter

   1. respirable particulate matter PM₁₀ (size < 10 um)

   2. fine particulate PM_2.5 (size < 2.5 um)

2. SO₂ - sulfur dioxide

3. CO - carbon monoxide

4. NO_x - nitrogen oxides

5. O₃ - Ozone

6. Pb - Lead (added later)

Total Ozone Mapping Spectrometer (TOMS)

Measures the total atmospheric ozone column by measuring UV region, at six wavelengths between 213 and 380 nm, in which few other atmospheric molecules absorb strongly

Suspended particulate matter

1. Natural sources of airborne particles, solid or liquid, including smoke, dust, sea, salt spray, pollen grains, bacteria, fungal spores

2. Liquid aerosols and particulates that are liquid are called mist, including fog and raindrops

Sources of CO

1. Anthropogenic sources of CO

   1. combustion of gasoline in confined ICE

      1. 2C₈H₁₈ + 17O₂ = 18H₂O + 16CO

   2. combustion by electric power plants

   3. industrial processes

   4. solid waste disposal

2. natural sources (10 times more CO than all anthropogenic sources combined)

   1. methane gas (released during anaerobic decay of plant materials in swamps, rice paddies, wetlands where vegetation is in oxygen-depleted water)

   2. methane from cattle/sheep termites

      1. food digestion produces methane, flows to bloodstream, released during exhale

   3. methane oxidizes to CO

      1. 2CH₄ + 3O₂ = 2CO + 4H₂O

mechanisms to maintain average global level constant at 0.1 ppm CO

1. conversion of CO to CO₂ in hydroxyl radical reactions

2. removal of CO from atmosphere by microorganisms in soil

total suspended particles (TSPs) in cities and effects

1. TSPs up to 200 ug m-3 have been measured in large cities

2. Individual measurements as high as 500 ug m-3 measured in dusty locations

3. Rural farming areas average 10g to 50 ug m-3

Chlorofluorocarbons (CFC) pollution

1. Besides refrigeration, CFCs are released directly into atmosphere

2. Tetraethyl lead, which was invented, is the octane-increasing additive for gasoline

3. Leaded gasoline partly responsible for global lead pollution

4. Commercially, the most important CFCs are halogenated methane Freon 11 and Freon 12

Tropopause

1. Top of troposphere

2. Low temperature (-57C) serves as barrier that freezes water vapor as ice crystals

Lithification

sedimentary rock formation

primary air pollutants

1. CO - carbon monoxide

2. SO₂ - sulfur dioxide

3. NOx - nitrogen oxides

4. VOCs - volatile organic compounds (mostly hydrocarbons HC)

5. Suspended particles

   Makes up approximately 90% of all air pollution in the US

fluidized bed combustion FBC

1. Process in which mixture of pulverized coal and powdered limestone burned, with air being introduced to keep mixture in semifluid state

2. Limestone converted to CaSO_4,

3. Coal finely divided, so reaction occurs at lower temperature than in flue-gas desulfurization FGD. As result, NOx emissions lower

4. Disadvantage of FBC is it cannot be added to power plants, but is preferred technology for new power plants

5. Both FGD and FBS have problem of disposing large quantities of CaSO₄

methane

1. 25 times more effective than carbon dioxide at trapping heat

2. steady rise attributed to increase in cattle and rice paddies

3. is polyatomic molecule with tropospheric concentration of 1.75 ppmb and increasing at a rate of 0.5% per year

4. Methane absorbs IR in 3 to 4 μm (not important because water and CO₂ already absorbed) and 7 to 8.5 μm (within atmospheric window, can contribute to greenhouse effect)

settling rate example: calculate settling rate for particulate of fly ash that is 2 μm in diameter and has density of 1.0 g/ml

1. Convert density into g/m³

   

2. Plug values into equation

   

3. Solve for settling rate (distance dropped in a specific unit of time)

   

Upper atmosphere

1. Extends beyond stratosphere

2. Divided into mesosphere and thermosphere

primary organic aerosols (POA)

organic particulate matter emitted directly as particles

CFC Substitutes

1. HCFCs (hydrochlorofluorocarbons) have less chlorine atoms nd break down more readily in troposphere, but cause ozone destruction

2. better substitute HFCs (hydrofluorocarbons), no chlorine. used in car ACs. can still contribute to climate change

Earth reradiates EMR as

infrared

Average wavelength of this radiating EMR, which is 10 um, which corresponds to the emission line for a 300 K black body emitter

NOx effects on human health

1. NO₂ is a red-brown toxic gas with unpleasant acrid odor

2. causes eye irritation, inflammation of lung tissue, and emphysema

3. concentration in atmosphere not high enough to produce symptoms

4. NOx is serious because of role in formation of secondary pollutants associated with photochemical smog

5. lowering combustion temperature of furnace decreases formation of NO, but decreases efficiency

Infrared absorption and molecule vibrations

1. Infrared radiation not energetic enough to break covalent bonds or cause electronic transition, but can change vibrational or rotational motion of a molecule

2. To absorb infrared radiation, molecule must undergo a net change in dipole moment as a result of vibrational motion or rotational motion around covalent bond

3. Because molecules are symmetrical, no matter how much covalent bonds stretched, no change in dipole moment

4. Therefore, these molecules which are principal constituents of the atmosphere, cannot absorb infrared radiation.

At altitude 6 km, atmospheric pressure reduced to

1. 50% of value at sea level

2. Average value used is 760 torr or 101,325 Pa

soot

1. Finely divided, impure form of carbon in which structure contains a series of fused benzene rings

2. Particles are spherical, whereas graphite forms flat layered structure

3. Product of incomplete combustion of coal

earth’s albedo

solar flux that is reflected back into space (31%)

percentages of solar flux absorption and reflection

1. Only approximately 69% of total solar radiation or solar flux reach Earth is absorbed. Remaining 31% reflected back into space

2. Of the 69% absorbed, 23% absorbed by water droplets in clouds and other gaseous molecules such as ozone in atmosphere

3. Remaining 46% absorbed and used for energy sources for biomass and thermal warming

Stefan Boltzmann Law

Energy reradiating from entire area of Earth’s surface Eout =

Steady-state total energy Earth absorbs from sun

1. Allows predicting average global temperature of -19C, but measurement is up to 15C

2. Calculation assumes that all radiation leaves Earth and is lost in space

3. If some IR radiation is absorbed by gases in the atmosphere and not lost, then planet’s temperature will be higher

Fly ash collection

1. Industry collects vast majority with electrostatic precipitation or bag houses

2. Majority of products used in construction-related applications, including cement and concrete, structural fills, soil stabilization, stabilization of waste, mineral filler in asphalt

Beer-Lambert/Beer’s Law

Relationship between the concentration of the absorbing molecule and absorbance (dimensionless)

1. Pathlength (b) can be very small (cm) or very large (km)

2. Quantity or molar absorptivity or extinction coefficient (ε), is characteristic of a molecule that indicates how much light it will absorb at a particular wavelength

Adsorption

if impacting molecules, become attached to the particle’s surface

Absorption

in the case of liquid particles, molecules are drawn inside and dissolved

Purpose of atmosphere

1. Shields the Earth’s surface from sun’s cancer causing UV radiation and moderates Earth’s climate

2. Stratified due to temperature and density relationships resulted from the interaction of physical and photochemical processes (induced by sun light)

Rayleigh-scattering

1. Light scattering by aerosols with dimensions that are significantly smaller than wavelength of radiation

2. Intensity is proportional to the inverse fourth power of the wavelength (S = 1/λ4)

temperature inversion

1. reversal of the usual temperature pattern

2. air temperature begins to increase instead of decrease with increasing altitude

3. colder denser layer cannot rise through warm lid of air and is trapped

4. no vertical circulation, so pollutants accumulate

nitric oxide measurements (chemiluniscene)

1. chemical reactions that release energy produced by emitting light rather than heat (fireflies)

2. NO in tailpipe emissions reacted with ozone

3. Two-step process.

   1. Ozone reacts with NO to produce excited-state nitrogen dioxide molecule (NO₂). electrons in NO₂ not in nlowest energy state but are in excited state

   2. NO₂ loses excess energy as the excited electrons return to ground state and emit excess energy as a photon of light

increase in atmospheric carbon dioxide

1. 20,000 years ago, concentration was approximately 200 ppm

2. Before industrial revolution at end of 19th century, 280 ppm

3. 1958 measurements at Mauna Loa, 315 ppm

4. 2000 measurements at Mauna Loa, 370 ppm

5. 30% increase in 100 years, mostly caused by burning of fossil fuels by electric facilities, automobiles, industry

null cycles

Processes that prevent certain species from taking part in catalytic cycles

in situ ozone measurements

1. Ultraviolet absorption used to measure concentration of ozone in stratospheric air

2. Other atmospheric gases (O₂, N₂ and H₂O) do not absorb UV radiation so do not have to be removed from air sample since they do not interfere with ozone measurement

3. Concentration of ozone in stratosphere is less than 10 ppm, so spectrophotometer must be capable of measuring small absorbance

4. Beer’s law states absorbance proportional to sample pathlength and because obtaining sample is easy, long sample pathlength greatly improves ability to measure ppm

XRF process

1. Incident x-rays cause sample to release photons. Emitted photons released from sample are observed 90 degrees to incident x-ray beam. Collects all photons simultaneously

2. Each photon strikes silicon waver treated with lithium and generates electrical pulse proportional to energy of photon

3. Pulse height proportional to energy of photon

4. Concentration of element determined by counting pulse number

nitric oxide journey up

1. Cars and truck engines release large quantities of nitric oxide (NO) into troposphere 

2. Almost all NO is oxidized to NO₂ then converted to nitric acid HNO₃

3. Rainfall washes nitric acid from troposphere before reaching stratosphere

4. Nitrous oxide N₂O is much less reactive than NO and eventually reaches stratosphere

5. N₂O is also tailpipe pollutant, but also released by soil during denitrification by anaerobic bacteria

6. Above 30 km, N₂O can absorb high-energy photons ton produce molecular nitrogen and excited oxygen atom O

humus

1. Soil sequester atmospheric CO₂ by containment of partially decomposed organic matter

2. While total amount CO₂ sequestered in soil unknown, improved soil conservation practices anticipated to help mitigate buildup of atmospheric CO₂ at least slightly

controlling SO₂ emissions

1. Sulfur removed from coal before combustion

2. SO₂ removed from smokestack after combustion but before reaching atmosphere

flue-gas desulfurization (FGD)

1. Sulfur-containing compounds washed out (or scrubbed) by passing the chimney (flue) gases through slurry of water mixed with ground limestone (CaCO₃) and or dolomite (CaMg(CO₃)₂) or both

2. On heating, calcium carbonate reacts with pacific SO₂ and oxygen to form calcium sulfate (CaSO₄)

3. Scrubber, which removes 90% of SO₂ in flue gas, easily retrofitted to existing power plants

Percentage water vapor in atmosphere

1. 0.1% to 5%, depending on temperature (vapor pressure of water increases with temperature), precipitation, rate of evaporation

2. Generally between 1% and 3% making it third most abundant constituent in air

Lowest temperature in atmosphere

-90C between 80-90 km elevation

Automobile pollutants

1. Motor vehicles are major source of CO, NOx, and volatile HCs

2. Cars emit 95% less pollutants than pre-1970 vehicles due to catalytic converters

3. NOx emissions difficult to reduce

4. NOx produced by four-cycle is near maximum at the ideal, stoichiometric air/fuel ratio

5. Lowering NO and HC can be done by two-stage combustion

   1. Operate system rich in fuel

   2. Operate system rich in air

6. Burns fuel completely, but not at high enough temperature to produce as much NOx

7. Stratified-charge engine uses this design to make most reductions in NOx emissions

Three-way catalytic converter

1. Reduces amount of HC, NOx, and CO in exhaust stream

2. Very fine honeycomb structure made of ceramic coated with precious metals platinum (Pt), and rhodium (Rh) which act as catalysts

3. Forces CO emission to form CO2, and NO to form N2

4. air-fuel ratio needs to be set at 14.8:1

Atmospheric Trace Molecular Spectroscopy (ATMOS)

1. Has sun tracker that keeps instrument’s field of view on sun, and a telescope that collects IR radiation to be processed by spectrometer

2. Spectrometer simultaneously measures concentrations of gases in stratosphere between 10 and 150 km altitude

3. Composition of stratosphere can be determined because gas molecules absorb specific wavelengths of incoming solar radiation by determining the wavelengths that have been absorbed

4. Has ability to detect gases in concentrations lower than 1 ppb

5. Disadvantages: can only take measurements at sunrise and sunset

6. Overcome by measuring atmospheric emission rather than absorption

Most harmful particles

1. Very fine particles (diameters less than approximately 1 um) most hazardous to human health

2. Not filtered by hairs and mucus in nose but drawn deep into lungs, causing tissue damage and contributing to the development of emphysema

Aerodyne aerosol mass spectrometer (AMS)

1. Able to measure OA concentration and mass spectrum

2. Analysis of spectra suggested that OA even in heavily polluted area much more oxygenated than expected

3. Comparisons of hydrocarbon-like HOA mass spectrum with those of vehicle emissions led to strong association of HOA and POA

4. Analysis of AMS data collected at sites revealed oxygenated organic aerosol OOA component dominated everywhere

Earth’s heat balance

1. As solar radiation travels through atmosphere, interactions with gases and particulates prevent approximately half from penetrating to Earth’s surface

2. 69% of solar energy reaching Earth includes entire visible region of spectrum with smaller portions of adjacent UV and IR regions

3. Incoming radiation largely absorbed at surface then reradiated back to space

4. If radiation away from surface did not occur, Earth would becoming increasingly warm as solar energy continued to flow in

5. Outgoing radiation from Earth is in longer wavelength IR region

Chlorine activation

1. In polar winter, chlorine-containing molecules accumulate

2. In spring, when sunlight returns to area, relatively inactive forms of chlorine in stratosphere such as ClONO₂ and HCl converted to photochemically active forms, such as Cl₂

3. Cl₂ produced can go on to attack ozone

Free radicals

1. Uncharged fragments of molecules that have unpaired electrons

2. Highly reactive and short lived

3. Responsible for many of the reactions that occur in the normal and polluted atmosphere

4. Central to chemistry of the troposphere is hydroxyl radical *OH, which is uncharged and different from negatively charged OH-

Ground state

1. Lowest energy state of a molecule

2. Very high-energy electromagnetic radiation, such as X-ray

3. Has enough energy to break chemical bonds and ionize molecules

Irradiance

1. Intensity or radiant power

2. Energy per second per unit area of the light beam (W/m²s)

3. Electromagnetic radiation passed through a monochromator to select one wavelength of electromagnetic radiation

4. Monochromatic light, with irradiance P0, passes into sample of length b

5. Irradiance of beam emerging from other side of sample is P

6. Some light may be absorbed by sample, thus p<=0

Stocks law

For particles in which the diameter exceeds 1um, the settling velocity V

Atmospheric window

Unobstructed region of spectrum between 7.5 and 13 um, through which infrared radiation from Earth’s surface can still escape

Carbon Dioxide on Earth

1. Combined infrared absorption of carbon dioxide and water coincide with most of the infrared emission from Earth

2. Emissions from the burning of fossil fuels primary anthropogenic source of CO2

3. Carbon store in fossil fuels sequestered for millions of years beneath surface un release through combustion process

4. Natural sources of atmospheric co2 include decomposition of organisms, plant and animal respiration, and ocean processes

5. Several important CO2 sinks, which are mechanisms that remove CO2 from the atmosphere operate on plant Earth

LIMS

1. limb infrared monitor of the stratosphere

2. Nimbus 7 satellite 1978, used to measure IR emissions of the Earth

3. Polar-orbiting satellite able to complete a picture of the entire stratosphere in one day

4. Radiance of thermal emission of Earth’s atmosphere much less than sun, therefore necessary to use broader spectral bands for measurement rather than a high-resolution spectrum

5. IR radiation from five spectral bands measured, enabling LIMS to measure global distribution of trace gases (CO₂, O₃, H₂O, HNO₃^-, NO₂)

Fly ash from coal-fired boilers

1. Produces approximately 1% to 2% fly ash, with diameter 0.1um

2. Accounts for largest number of particles and most surface area

3. Contains Fe, Zn, Pb, V, Mn, Cr, Cu, Ni, As, Co, Cd, Sb, and Hg

4. Smaller fly ash is inhalation risk, because less likely to be trapped in nose of larynx and more likely to be inhaled into deep recesses of lung

Ozone production in stratosphere

1. Concentration of O₃ greatest at altitude 20 to 30 km

2. Formed when ordinary molecules O₂ in the stratosphere absorb UV radiation from sun with wavelength of less than 240 m, causing them to dissociate into single oxygen atoms

Polyatomic molecules

1. molecules made up of more than two atoms or elements, held together by covalent bonds

2. All gases that contribute to greenhouse effect

3. Have numerous vibrations

4. Two most greenhouse gas polyatomic greenhouse gases CO₂ and H₂O

5. Approximately 89% of 34 K temperature increase resulting from greenhouse warming attributed to water. CO₂ accounts for 7.5%

Radiative forcing

1. Decreases in stratospheric ozone concentration have cause cooling, while increases in tropospheric ozone concentration have caused warming

2. Aerosol particles affect radiative forcing:

   1. Aerosols can reflect incoming solar radiation, which causes negative forcing

   2. They can absorb IR radiation that would be lost from surface of Earth ,causing positive forcing

3. If radiative forcing for all aerosols is summed, effect of aerosols is negative

VOC/NOx ratio

1. At high ratio of VOC to NOx concentrations, OH will react mainly with VOCs,

2. At low ratio NOx reaction can predominate

air pollution sources

1. Transportation and industry responsible for 50% of air pollution from anthropogenic sources

2. Automobiles emit NOx, HCs, and CO

3. Burning of fossil fuels by stationary sources account for one third of air pollutants, in the form of sulfur oxides

Terpenes

volatile, unsaturated 5-carbon cyclic compounds

Nitrous oxide

1. Absorbs IR radiation in the 3 to 5 um and 7.5 to 9 um (atmospheric window) region

2. Concentration of nitrous oxide in atmosphere is 314 ppbv and increasing by 0.3% per year

3. Major source is released from soil, lakes, oceans, by microbial denitrification of nitrate

Positive feedback

1. Occurs when global warming increases evaporation from oceans that leads to higher concentrations of water vapor in air

2. Increased amount of water vapor causes more infrared radiation to be absorbed, and increases warming of Earth’s surface

Mass composition of atmosphere

1. Troposphere and stratosphere account for 99.9%

2. Half of mass concentrated within 6 km of Earth’s surface

3. Air above each square inch of surface at sea level exerts 14.7 pounds

Free troposphere

1. continuously radiates energy upward, cooling upper troposphere

2. Troposphere itself does not efficiently absorb solar radiation

3. Region receives warmed air that rises from surface

WHO guideline of particles

PM2.5 = 15 ug/m³ for 24 hour average concentration and 5 ug/m³ for annual mean

Solubility pump

1. Oceans remove CO₂ from atmosphere by dissolving gas

2. Cold polar ocean water at surface dissolves atmospheric CO₂

3. CO₂ rich surface water sinks into deep ocean where it is sequestered for several hundred years

4. Sink is expected to become less important as polar regions become warmer

LIDAR

1. Light detection and ranging, similar to radar

2. Radar transmitter sends radio waves, and radar detector measures time it takes to bounce off an object and return to detector

3. Operates in the visible and infrared regions

4. Transmitter is laser, receiver is optical telescope that is focused on an extremely sensitive photomultiplier detector

5. Detector records photons that reach it and converts response to electronic signal

vegetation

1. Nonsoil component of biosphere

2. Absorbs CO₂ during photosynthesis and stores carbon in biomass

3. 30% of Earth’s surface is land and only 30% of land covered by forests

4. Vegetation is smaller sink than ocean and slightly smaller than soil

5. Within biosphere, most critical region for sequestration is tropical rain forest

Negative feedback

Occurs as troposphere becomes cloudier, and that causes more reflection of incident solar flux, causing cooling of Earth’s surface

Atmospheric Composition

1. Nitrogen 78% oxygen 21%

2. Argon 0.93% carbon dioxide 0.037%

3. Smaller amounts of neon, helium, krypton, methane

Catalytic converter basics

1. At 25C, efficiency near zero

2. Ineffective when starting a cold engine, and low during warm up

3. Lead-free gasoline must be used because lead coats and inactivates catalysts

4. Today’s catalytic converters remove 96% of CO and HCs and 76% of NOx from exhausts

Exposure and treatment for CO poisoning

1. Inhalation of pure oxygen, reversing direction of reaction

2. Symptoms of CO poisoning: headache, dizziness, impaired judgement, drowsiness, slowed reflexes, respiratory failure, loss of consciousness and death

3. Prolong explore to CO levels as low as 10 ppm can be harmful

4. Colourless, tasteless, and odourless

5. Concentration may reach 50 ppm on streets, and higher underground garages/traffic

Absorbance

Directly proportional to concentration C of the absorbing molecule in sample

aerosols

1. Minute particles with diameters of less than approximately 10um

2. Have very large surface areas that act as sites for chemical interactions

3. Chemical reactions may occur at surface or within

particulates

a mixture of particles in the air, larger than aerosols

greenhouse effect

1. Warming effect caused by absorption and reradiating of IR radiation by greenhouse gases

2. Gases act like glass in a greenhouse

3. Visible light passes through glass and is absorbed by objects inside greenhouse

4. Objects warmed and emit heat energy in form of IR radiation which cannot pass through glass, therefore heat is trapped inside

5. greenhouse gases: co2, water vapor, methane, nitrous oxide, cfcs, ozone

secondary organic aerosol formation

1. Principal atmospheric oxidants are hydorxyl radical (*OH) ozone (O₃), and nitrate radical (NO₃^-)

2. In SOA formation, several generations of gas-phase oxidation occur, each generation producing compounds of decreasing volatility

Effects of CO on human health

1. Interferes with oxygen carrying capacity of blood. 

2. Normally, Hemoglobin in red blood cells combine with oxygen to form OxyHemoglobin (HbO₂)

3. HbO₂ carried in bloodstream to parts of the body, where oxygen is released to tissues

4. CO binds stronger to Hv than oxygen. If CO is present, it displaces oxygen from Hb and reduces amount of oxygen that can be delivered to tissues

hydroxyl radicals

1. Continually formed and consumed in troposphere and are produced as a result of a series of complex reactions primarily involving ozone, water, and nitrogen dioxide

2. Play a role in removal of CO and HCs from atmosphere and in the formation of nitric acid, sulfuric acid, and photochemical smog from atmospheric gases

Aerosol particles

1. Effect of particulate matter on heat flux depends on particle size and not as much total concentration

2. Large dark particles absorb light and add to warming of atmosphere

3. Small particles scatter incident sunlight and increase the albedo of the atmosphere

4. Natural sources of light-scattering aerosols are estimated to produce 50% to 75% of all atmospheric aerosols

UV spectrometer for ozone measurement

1. Uses a low-pressure mercury lamp to produce electromagnetic radiation

2. Output of mercury lamp has a maximum at 254 nm, very near to absorbance maxima for ozone

3. Tube carrying air split into two streams

   1. One passes through ozone scrubber removing ozone and air acts as reference

   2. Other with ozone travels to sample cell

4. Each stream flows through one 50-cm sample cell

5. Light from mercury lamp sent down, silicon photodiode at end detects intensity

6. Ozone contraction 1ppm produces absorption 0.2

Troposphere

1. 10-16 km above earth

2. Temperature decreases steadily as distance from Earth’s surface increases until -57C

Peroxyacetyl nitrate (PAN)

1. Component of smog that causes major irritation

2. Stable molecules with long lifetimes in cooler air, reservoir for NOx

3. PANs break down in warmer climates to release NO₂ and releases ozone and hydroxyl radicals

Major natural source of aerosols

1. Ammonium sulphates generated during microbial degradation of decaying biomass and organic matter in soil and water

2. Reactive organic molecules that are released from natural sources

3. EX. release of organic molecules, terpenes, from coniferous trees.

Industrial sources of emissions

1. Waste incineration and kiln drying of cement emit metals

2. PM from industrial process contains Fe₂O₃, Fe₃O₄, Al₂O₃, SiO₂, carbonates of several metals

3. Heavy metals vaporize at high temperature and then recondense onto particles that are formed simultaneously

4. Iron released into atmosphere far more than any other metal

5. Lead is emitted form lead-ore smelters and lead-acid battery manufacturing

Fate of atmospheric NOx

1. NO₂, regardless of source, is ultimately removed from atmosphere as nitric acid and nitrate in dust and rainfall

2. NO₂ combines with water vapor to form nitric acid

3. Much of nitric acid in atmosphere formed within aqueous aerosols

4. Some nitric acid form reacts with ammonia and metallic particles to form ammonium nitrate

5. Nitrates dissolve in rain and snow or settle as particles, contributing to acid deposition

secondary air pollutants

Harmful substances produced by chemical reactions between primary pollutants and other constituents in atmosphere

e.g. Sulfuric acid, nitric acid, sulfates, and nitrates, and ozone, and other photochemical oxidants

POA

1. Primary organic aerosols, emitted directly as particles from combustion sources such as transportation and biomass burning remaining in particulate form, serving as inert nuclei in which secondary organic components condense

2. Sufficiently volatile that it evaporates after emission

3. Once emitted, is diluted and evaporates, then resulting semivolatile organic vapors react in gas phase with OH radical and other atmospheric oxidants, forming low-volatility oxidation products

4. Evaporation-reaction-recondensation cycle leads to significant changes in chemical nature of primary OA and is one of the reasons why organic aerosol in large urban areas with considerable organic particulate emissions is dominated by oxygen containing compounds

Blue light

1. Shorter wavelength, more scattered than red

2. Sky, seen in scattered light = blue

3. Sunset, seen in transmitted light = red

Average solar flux reacting the earth (at the top of the stratosphere)

1368 W/m²

Average surface temperature of the Earth

288 K (15C)

Temperature above mesosphere

1. Rises to 1200C in atmosphere

2. Caused by few gaseous molecules in thermosphere absorbing most energetic radiation emanating from sun

biological pump

1. Marine phytoplankton take in atmospheric CO2 and released carbon in a form that sinks to ocean floor where it is sequestered through lithification of sedimentary rocks

2. Process estimated to reduce atmospheric CO2 by ⅓

Electrostatic precipitation

1. Method to control particulate emissions

2. Gases and particulate matter passed through high-voltage chamber before leaving chimney stacks

3. Negatively charger central electrode imparts a negative charge to particles

4. Then attracted to positively charged walls of chamber

5. As charges neutralized, particle clump together and fall to bottom to collect

TSP test

1. Total suspended particle test measuring total amount of suspended particle matter

2. Air drawn through pre weighed filter at rate of 1 m³h^-1

3. Total time air pumped is recorded so total volume of air passing known

4. At end, filter weight again so total weight of particulate matter known

Montreal protocol

1. 1987 first international effort to protect ozone layer, calling for CFC production to be cut back to 5%

2. Amended in 1992, when 140 nations agreed to end CFC production by 1995 and speed phaseout of ozone-depleting chemicals

3. Target chemicals: CCl4, CH3Br, HCFCs

4. CFC-11 and CFC-12 lifetimes approximately 55 and 116 years