Transcript Oxygen (O 2 )

Energy and the Environment
Fall 2013
Instructor: Xiaodong Chu
Email：[email protected]
Office Tel.: 81696127
Flashbacks of Last Lecture
• Air pollution
– Air-quality modeling
– Photo-oxidants
– Acid deposition
• Water pollution
• Land pollution
Air Pollution Cases: Smog And Haze
Primary Pollutants
CO CO2
SO2 NO NO NO2
CH4 and most
other hydrocarbons
Most suspended particles
Natural
Source
Stationary
Secondary Pollutants
SO3
HNO3 H2SO4
H2O2 O3 PANs
Most NO3– and SO42– salts
Human Source
Human Source
Mobile
Sources and Types of Air Pollutants
Industrial Smog
• Chemical composition of industrial smog
• How pollutants are formed from burning coal
and Oil, leading to industrial smog?
Ammonium sulfate [(NH 4 )2SO4]
Ammonia (NH3)
Sulfuric acid (H2SO4)
Carbon monoxide
(CO) and carbon
dioxide (CO2)
Water vapor (H2O)
Sulfur trioxide (SO3)
Oxygen (O2)
Sulfur dioxide (SO2)
Burning coal and oil
Oxygen (O2)
Sulfur (S) in coal and oil
Carbon (C) in coal and oil
Photochemical Smog
• Photochemical Smog
– Chemical composition
– Sources
• VOCs + NOx + Heat + Sunlight yields
– Ground level O3 and other photochemical oxidants
– Aldehydes
– Other secondary pollutants
PANS and other pollutants
Volatile organic
compounds (VOCs)
Ozone (O3)
Oxygen (O2)
Nitric oxide (NO) +
Oxygen atom (O)
Hydrocarbons
Peroxyacyl
nitrates (PANs)
Water
vapor
(H2O)
UV radiation
Nitrogen dioxide (NO2)
Oxygen (O2)
Nitric oxide (NO)
Oxygen (O2)
Burning fossil fuels
Nitrogen (N) in fossil fuel
Ingredients of Photochemical Smog
• Three main ingredients of photochemical smog
– High automobile traffic volume
– Plenty of sunlight
– Very stable atmosphere
• Temperature inversion
Temperature Inversion
• A temperature inversion occurs when cold air is
trapped near Earth’s surface by a layer of warmer air
• Polluted air can then be trapped near Earth’s surface
Temperature Inversion
• Temperature inversions can occur during cold, cloudy weather
in a valley surrounded by mountains
• Frequent and prolonged temperature inversions can also
occur in an area with a sunny climate, light winds, mountains
on three sides, and the ocean on the other
– A layer of descending warm air from a high-pressure system
prevents ocean-cooled air near the ground from ascending
enough to disperse and dilute pollutants
Continental Surface Visibility (Human Observers)
NOAA NCDC Global Summary of the Day (SOD) 7000 Observations
Low Visibility
High Visibility
Regional Haze
• Regional haze is visibility impairment that is produced by many
sources and activities which emit fine particles and their precursors
and which are located across a broad geographic area
• Pollutants come from a variety of natural (e.g., windblown dust, soot
from wildfires) and manmade (e.g., motor vehicles, electric utility and
industrial fuel burning) sources. Some haze-causing particles are
directly emitted to the air while others are formed when gases
emitted to the air form particles as they are transported.
• Haze is caused when sunlight encounters tiny pollution particles in the
air. Some light is absorbed by particles. Other light is scattered away
before it reaches an observer. More pollutants mean more
absorption and scattering of light, thus reducing the clarity and
changing the color of what one sees. Some types of particles, such as
sulfates, scatter more light than others, particularly during humid
conditions.
February 2001
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Regional Haze
• Regional haze arises when the contributions of many
individual sources are mixed together during long range
transport
• The resulting spatially uniform hazy air mass can cover
multi-state areas in excess of 1000 km in size
Global Pattern of Haze Based on Visibility Data
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A rough indicator of PM2.5 concentration is the extinction coefficient corrected for weather conditions and
humidity. There are over 7000 qualified surface-based visibility stations in the world.
The June-August haze is most pronounced in southeast Asia and over sub-Saharan Africa where the seasonal
average PM2.5 is estimated to be over 50 g/m3.
Interestingly, the industrial regions of the world such as eastern North America, Europe and China-Japan
exhibit only moderate levels of haze during this time.
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Case Study: Los Angeles Air Quality
Photochemical smog in downtown Los Angeles, California (USA)
Ingredients of Photochemical Smog
• Due to the lack of efficient public transportation,
residents there depend on their cars
• Los Angeles’ climate is dominated by the Eastern
Pacific High
– Subsidence also produces clear condition and hence more
sunlight
– Subsidence produces compression heating of the air, and
the temperature is often higher at a few hundred feet level
than at surface – an inversion condition, an absolutely
stable condition
• The topography of Los Angeles – a basin also helps to
trap air pollutants
Valleys Trap Pollutants
L.A. is in a basin surrounded by
mountains that trap pollutants and
usually has onshore flow that creates
frequent inversions.
Pollutants can only escape through
narrow canyons
Sources of Smog in Los Angeles
Typical Daily Concentration Variation
of Smog Chemicals
Case Study: Asia Brown Cloud
• Particles from airborne
pollution, such as the "Giant
Brown Cloud," can travel all
around the globe. In April of
2001, NASA satellites saw a
massive dust storm appear
over China. The densest
portion of the aerosol
pollution traveled east over
Japan, the Pacific Ocean,
and, within a week, the
United States.
—— NASA
Asia Brown Cloud: Causes
Clearing forest and burning fossil
fuels
• Clearing and burning forest for planting crops
• Burning of coal, diesel, and other fossil fuels in
industries , vehicles and homes
Asia Brown Cloud: Chemical
Composition
Dust, smoke and compounds
• 1/3 of it is dust, smoke, and ash
• Rest is acidic compounds, soot, toxic metals (mercury
and lead), hundreds of organic compounds and fly
ash
Asia Brown Cloud: Areas Impacted
South Asia
• Much of India, Bangladesh
• South of China
• Open Sea east of this area
Asia Brown Cloud: Impacts
Environment and health
• Photosynthesis has been reduced by 7-10%
• Acid in the haze fall to the surface and damage crops,
trees, and aquatic life
Case Study: 1997 Southeast Asian
Haze: Causes
Farmers’ method of clearing the land
• Indonesian farmers carry out the “slash-and-burn”
method to make land for crop-planting
• Setting fire to large pieces of land to burn down trees
and leave only bare ground
• Cheapest and fastest way to obtain clear land
• Serious implications – severe haze contaminates air
in neighbouring countries
1997 Southeast Asian Haze: Causes
Large Corporations: Timber and palm
plantations
• Corporations want the cheapest way to clear space
to start plantations – save money
• Employ workers to set forest-fires
• Inconsiderate and unethical in the long run
• Damage the environment
1997 Southeast Asian Haze: Impacts
TOMS for 1997 Southeast Asian haze
1997 Southeast Asian Haze: Impacts
Environment
• Disruption in ecosystem
– Flora and fauna burnt and lost
– Endangers more species of animals
– Destroys rare species of organisms
• Pollute the air – pollutants blown to neighboring
countries (transboundary pollution)
1997 Southeast Asian Haze: Impacts
Environment (cont’d)
• Fires produce greenhouse gases
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Sulphur Dioxide
Ozone
Nitrogen Dioxide
Carbon Monoxide
• Affects atmosphere negatively
• Speeds up global warming
– Shifting climate changes
– Unpredictable weather
1997 Southeast Asian Haze: Impacts
Health
• Triggeres off health conditions
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–
–
–
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Respiratory related problems
Asthma attacks
Bronchitis
Coughing / wheezing
Runny noses
Sore throats
Eye / skin irritation
Heart conditions
1997 Southeast Asian Haze: Impacts
Health (cont’d)
• Haze particles (Ozone, Sulphur Dioxide) cause
damage to lungs and hearts
• Particulate Matter 10 (PM10) cause lungs to function
at decreased rate – shortness of breath
1997 Southeast Asian Haze: Impacts
Tourism
• Flights disrupted (13 cancelled) and delayed
• Tourists shun countries affected by haze
• Tourists stranded at the airport as they have already
checked out of hotels
• Unsatisfied and unhappy about their vacations
1997 Southeast Asian Haze: Impacts
Economy
• Surge in medical costs
– Treatment of cough
– Other haze-related illnesses
• More people ill; less people turn up for work –
reduce efficiency of different industries during that
period
• Retailers and recreation businesses affected – most
people try to stay at home during the haze period
Laws and Regulations Can Reduce
Outdoor Air Pollution
• United States
– Clean Air Acts: 1970, 1977, and 1990 created regulations
enforced by states and cities
• EPA
– National ambient air quality standards for 6 outdoor pollutants
– National emission standards for 188 hazardous air pollutants
(HAPs)
• Toxic Release Inventory (TRI)
The Clean Air Act
• Authorizes EPA to set limits
on amount of specific air
pollutants permitted
• Focuses on 6 pollutants:
– lead, particulate matter,
sulfur dioxide, carbon
monoxide, nitrogen oxides,
and ozone
• Act has led to decreases
Laws and Regulations Can Reduce
Outdoor Air Pollution
• Good news in developed countries
– Decrease in emissions
– Use of low-sulfur diesel fuel
• Cuts pollution
• Less-developed countries
– More air pollution
Case Study: U.S. Air Pollution Can
Be Improved
• Rely on prevention of pollution, not cleanup
• Sharply reduce emissions from power plants,
industrial plants, and other industry
• Raise fuel-efficiency for cars, SUVs, and light
trucks
• Better regulation of emissions of motorcycles
and two-cycle gasoline engines
Case Study: U.S. Air Pollution Can
Be Improved
• Regulate air pollution for oceangoing ships in
American ports
• Regulate emissions at U.S. airports
• Sharply reduce indoor pollution
• Increased and more accurate monitoring of air
pollutants
There Are Many Ways to Reduce
Air Pollution
• There are ways to deal with
– Stationary source air pollution
– Motor vehicle air pollution
• New cars have lower emissions
Stationary Source Air Pollution
Motor Vehicle Air Pollution