the atmosphere and atmospheric pollution the atmosphere and atmospheric pollution

The Atmosphere and Atmospheric Pollution

http://apod.nasa.gov/apod/ap120305.html

http://apod.nasa.gov/apod/ap120305.html

Atmospheric Components

• Chemical Components (elements)–Nitrogen gas (N2) makes up about 78% of

the atmosphere–Oxygen gas (O2) makes up about 21%–Other gases (Ar, He, etc.) <1%


• Most abundant compounds:–Carbon dioxide (CO2)–Water vapor varies greatly• Evaporation ()• Transpiration by plants ()• Precipitation, condensation ()


• Other components–Ozone (O3) - UV filter in upper

stratosphere; bad in troposphere–Dust - from volcanoes, sandstorms,

fires, etc. (pretty sunsets!)

Atmospheric Layers

Troposphere:• Closest to the Earth’s surface• All weather changes take place here• Most of CO2 and H2O vapor here• Height varies from about 20 km at equator

to about 8 km at poles - Why?• Temperature decreases with height

Atmospheric Layers

Stratosphere• Contains almost all the ozone (O3) in the

atmosphere 3O2 +UV 2O3

• Temperature rises with altitude• Gases released from volcanic eruptions

stay here for years• Tops of thunderclouds can penetrate

OUTDOOR AIR POLLUTION

Outdoor Air Pollution

The presence of atmospheric chemicals at concentrations high enough to harm organisms, ecosystem, or human-made materials

Come from natural sources: dust, wildfires, VOCs (plants)

Come from human sources: near industrialized/urban areas


Is air pollution a recent development?


Primary Pollutants: • emitted directly into the airSecondary Pollutants:• Products of chemical rxns of 1⁰ pollutants• Good news?• Bad news?• What is the biggest pollution threat to

poor?


Point source: specific spots where large quantities of pollutants are discharged (power plants and factories)

Nonpoint source: more diffuse, consisting of many small sources (automobiles)


Carbon Oxides:CO and CO2

• CO a result of incomplete combustion• CO from vehicle exhaust, tobacco smoke, forest

fires, inefficient stoves, furnaces• Chronic exposure to CO: heart attacks, lung

diseases• Acute exposure to CO: headache, nausea,

drowsiness, death


Carbon Oxides:CO and CO2

• CO2 in the atm: 93% a result of carbon cycle, rest is from human activity

• Considerable evidence: human-introduced CO2 is changing the climate


Nitrogen oxides (NOx):Nitric oxide (NO)• Formed from high-temp engines, coal plants,

lightning, bacteria (N-cycle)2NO + O2 → 2NO2 (brownish gas; photochemical

smog)2NO2 + H2O → 2HNO3 (acid deposition)• Eye, nose, throat irritant, aggravate lung ailments


Sulfur oxides (SOx):Sulfur dioxide (SO2)• One-third comes from S cycle• Rest from coal-burning plants, oil refining,

smelting• Converted to aerosols of H2SO4 – more on this

later


ParticulatesSolid particles and liquid droplets small enough to

remain suspended• ~62% from natural sources• Human input: coal, cars, plowed fields, road

construction, tobacco smoke• Fine (< 10μ) and ultrafine (<2.5μ) particles most

damaging


Particulates• Aggravate asthma, bronchitis• Shorten lifeToxic particles (Pb, Cd, PCBs)• Cause mutations, reproductive problems, cancer• According to EPA: 60-70,000 deaths


Ozone• Part of smog• Causes coughing, breathing problems, aggravates

heart and lung disease• Reduce resistance to colds, etc.• Irritant; damages plants, fabrics, tires, paints• Good O3 v. bad O3


Volatile Organic Componds (VOCs)• Organic cpds that exist as gas• Most are hydrocarbons• Methane is one example• Others: benzene, trichloroethylene, vinyl chloride

are industrial solvents• Benzene →→ leukemia, blood disorders, immune

damage, et al.


Industrial Smog• Main components: SO2, H2SO4, other particulates

• Most of carbon in coal, oil → CO, CO2, soot• Ammonium sulfate also produced• Not as problematic in developed countries


Photochemical Smog• Activated by light• A mixture of 1⁰ and 2⁰ pollutants• Reactants: VOCs + NOx + sunlight

• Products: O3, aldehydes, oxidants, HNO3, peroxyacyl nitrates (PANs)

• Hotter days: more ozone• Natural smog: Smokey Mountains (terpenes)


Factors Affecting: natural reduction• Settling• Precipitation• Ocean spray wash-out• Winds• Chemical reactions


Factors Affecting: increase• Urban buildings slow winds• Hills/mountains• High temperatures (↑ rxn rates)• VOCs from oak, poplar trees, kudzu• Grasshopper effect – transport by global winds• Temperature inversion

Outdoor Air Pollution Control

Prevention, Technology, Innovation• Fluidized bed combustion: coal burned w/ CaCO3,

produces CaSO4, which is used to make sheetrock

• Controlling T and O2 can reduce NOx

• Catalytic converters also reduce NOx (also led to removal of Pb from gasoline)

• Control of particulates: baghouse filters, electrostatic precipitators, scrubbers

Outdoor Air Pollution Control

Prevention, Technology, Innovation• Municipal restrictions developed, including

restrictions on dry-cleaners, gas stations, even bakeries (oh, no!), car use restrictions, carpool lanes

• Clean Air Act amendments → reduced sulfur emissions; buying and selling of allowances that allowed release of certain amount of S

ACID DEPOSITION

Acid Deposition

Industry Smokestacks• Reduce local air pollution• Increase regional pollution as SOx and

NOx are carried downwind• Sulfuric and nitric acids are formed

Acid Deposition

Acid Deposition• Remain in atmosphere 2 – 14 days• Fall as wet deposition (rain, snow) or dry

deposition (crystals)• Some regional soils can buffer• Worst acid deposition - Asia

Acid Deposition

Effects• Respiratory disease• Damages human-made structures• Leach toxic chemicals from soils/rock• Aquatic systems (ΔpH, release Al3+)• Forest, crop damage

Acid Deposition

Reduction• Reduce coal use/use low-sulfur coal• Increase natural gas, renewable energy• Remove SOx and NOx from smokestacks• Tax emissions• Cleanup: lime to lakes, phosphate

fertilizer

INDOOR AIR POLLUTION

Indoor Air Pollution

Common Pollutants• Pesticides, lead (brought in on shoes)• Organic solvents• Dust mites, droppings• Molds and mildews• Formaldehyde & other VOCs• Radon


Alarming Facts (more harmful than outdoor)• Levels are generally higher in homes and

cars (5x, 18x, respectively)• In developed countries, people spend

more time inside• EPA: 18 indoor pollutants on carcinogen

list


Sick Building Syndrome• Due in part to increased insulation• Indoor levels of VOCs and other

materials increase• Synthetic materials (glues, etc)• Ventilation, chemical contamination, air

intake, biological contamination

HEALTH EFFECTS

Health Effects

Natural Defense• Simple columnar epithelium contains

cilia and produce mucus• This line of defense gets broken down• Particulates embed in alveoli• Emphysema is irreversible; alveoli

damaged, lose surface area

DEALING WITH AIR POLLUTION

Legislation addresses pollution• Congress passed a series of laws starting in 1955• The Clean Air Act of 1970– Sets standards for air quality, limits on emissions– Provides funds for pollution-control research – Allows citizens to sue parties violating the standards

• The Clean Air Act of 1990– Strengthens standards for auto emissions, toxic air

pollutants, acidic deposition, stratospheric ozone depletion

– Introduced emissions trading

Laws

Ambient Air Quality Standards• Standards for 6 criteria pollutants – CO,

NOx, SO2, O3, Pb, & particulates• Standards for 188 hazardous chemicals• Public record: Toxic Release Inventory

the atmosphere and atmospheric pollution the atmosphere and atmospheric pollution

Documents

atmospheric pollution

atmosphere oxygen gas

gases ar