Transcript Air Pollution

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 Converters
Solution??
• Converts toxic exhaust from an internal
combustion engine into less noxious byproducts
– 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 Pollutants
Standards 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