Earth’s Atmosphere and Air Pollution

Chapters 20 and 21

Earth’s Atmosphere

Air Pollution

Outdoor Air Pollution

• Comes from Stationary or Mobile sources

• Two Categories:– Primary: those emitted directly

• Ex’s: CO, CO2, SO2, NO, NO2

– Secondary: primary pollutants that react to

form new pollutants• Ex’s: SO3, HNO3, O3, PANs

• Brown Air Smog– Los Angeles

San Francisco

Photochemical Smog (brown)

• SUNLIGHT is a catalyst

• NOx-based

–COMBUSTION: (internal combustion engines – high temps)

–NATURAL: N-cycle, volcanoes, fires, lightning

• VOC’s: VOLATILE ORGANIC COMPOUNDS –evaporate/vaporize under

“normal” conditions–approx. 600 in the atmosphere–solvents, fuels, paints, cleaning

supplies, adhesives/glue, pesticides

–PLANTS: terpenes

• Reactions

–Cars (and CFPP’s) release NO and NO2 (NOx)

• Gray Air Smog– Satellite images

of China

Los Angeles

Industrial Smog (gray)

• Sources:– Mostly coal-fired power plants– Cars

• Reactions:– Mostly carbon and sulfur based– Chemistry:

What’s so bad about air pollution anyway????

• Human health

–Asthma/bronchitis/emphysema

–Eye irritant

–Nose and throat irritants

–Cancers

–“According to the World Health Organization, at least 3 million people die prematurely each year from the effects of air pollution”.

Not to mention…

• Climate change

• Stratospheric Ozone Depletion

Factors That Influence Smog

• Reduce:–Rain and snow: cleanse the air

–Salty sea spray: washes the air

–Winds: sweep pollution away

• Increase–Urban buildings: block wind flow–Hills/mountains: block wind flow–Temperature: higher temps

promote reactions–Grasshopper Effect: wind currents

carry tainted air to the poles–Temperature inversions: layer of

warm air lies on top of cool air – acts as a lid

Temperature inversion

Mountains/hills exacerbate inversions

Grasshopper effect

NEWSPAPER HEADLINES:

• “Arctic Indigenous Peoples Being Poisoned by Industry Thousands of Miles Away”

• If you think the pollution in New York, Los Angeles or Detroit is scary, consider this: Arctic indigenous peoples often have levels of persistent organic pollutants (POPs [3]) in their blood and breast milk that are 10 times higher than the residents of major American cities.

• Individuals living near industrial hubs expect to bioaccumulate a certain amount of toxic chemicals, but for aboriginal peoples living near the Arctic Circle, thousands of miles from the sources of these chemicals, the levels are both astonishing and disturbing.

• The pollution is the result of what scientists call the “grasshopper effect [4]”, in which transboundary pollution [5], dispersing at the point of origin and driven by wind, re-volatilizes (or comes down to earth and oceans) thousands of miles away in the Arctic.

Pesticide DDT shows up in Antarctic penguins

• Acid Deposition

Water, soil, vegetation greatly affected:

Effects such as chemical weathering:

CaCO3 (s) + H2SO4 (aq) → CaSO4 (aq) + CO2 (g) + H2O (l)

“Clean” Coal Technology… Solution?

• Coal that contains 2% - 4% sulfur is considered HIGH sulfur coal.

• Coal that contains less than 2% sulfur is considered LOW sulfur coal.

Either way, when we burn coal to produce electricity, sulfur is released into the atmosphere!!

Removing the sulfur:

• PRE-combustion:

– Coal washing: removes unwanted minerals such as sulfur by mixing pulverized coal with a liquid and allowing the impurities to separate.

• POST-combustion: (Figure 20-18)

– Electrostatic Precipitator: removes particulates (that cause things such as asthma) by charging particles with an electrical field and capturing them on collection plates.

–Baghouse Filter: removes many of the more hazardous fine particulates.

– Cyclone Separator: particles that can not follow the cyclone stream of air, strike the wall of the separator, and fall to the bottom. (least expensive)

– Wet Scrubber: removes 98% SO2 and particulates; spray or immerse gas with limestone and water – the mixture reacts to form gypsum, a component of drywall. (expensive to install and maintain)

Cars have Catalytic ConvertersSolution??

• Converts toxic exhaust from an internal combustion engine into less noxious by-products– Convert CO (Carbon Monoxide) and VOC’s

(Volatile Organic Compounds or unburned hydrocarbons) into CO2

– Convert NOx gases into Nitrogen gas and Oxygen gas

Preventing/Reducing Air Pollution

•Clean Air Acts – (1970, 1977, 1990)– EPA established NAAQS – National Ambient

Air Quality Standards for 6 outdoor pollutants (set maximum permissible levels)

– 1– 2– 3– 4– 5– 6

•Primary Standard = protect human health

•Secondary Standard = prevent environmental and/or property damage

• EPA established emission standards for HAP’s – Hazardous Air PollutantsStandards set for 188 HAP’s, (most are VOC’s, hydrocarbons, and toxic metals)

• TRI – Toxic Release Inventory = source for info about HAP’s in your area

•Emissions Trading Policy (Cap’n Trade) = (CAA of 1990)

–Help to reduce ________emissions

• A limit (cap) is set on the total amount of a pollutant that can be emitted (SO2), the limit is allocated/sold to groups (power plants, factories, environmental groups) in the form of emissions credits

• The TOTAL number of credits can not exceed the TOTAL cap, groups that need more credits because they pollute more must BUY them; those that pollute less can SELL them

–POLLUTERS PAY! (But it the cap is set too high… nobody pays)

–Companies have certain numbers of pollution credits

»Emit less = keep what’s left for future or emissions at other plants or sell

•  

Ozone Depletion• Chemistry:

Indoor Air Polltion• asbestos

Asbestos…

• Insulating materials – Resists heat and cold

• Floor coverings– Resists humidity and scratches

– Needs to be

professionally removed!

• Asbestos lung: mesothelioma

• Radon

• Uranium-238 → Radon-222–Series of alpha and beta decay

–Review: What are the alpha and beta particles???

Source: EPA

Carbon monoxide