Start off with a tale – when is a lichen like a canary?
19th century coal miners knew that when canary would quit singing, air quality was getting poor (too much methane). So the canary was in a sense an “indicator” species, alerting the miners to a negative change in the environment. Lichens can also warn us of poor air quality. Lichen consist of both a fungus and an alga (algae) living together. They absorb air and some are sensitive to air-polluting chemicals such as SO2, sulfur dioxide. Miller notes that we can use the lichen to track pollution to its source too. Scientist used lichen to track SO2 found on Isle Royale in Lake Superior to coal-burning powerplant at Thunder Bay, Ontario to the north. Showing how the food chain operates, Miller cites a story of lichens in Lapland absorbing radioactive particles from Chernobyl explosion in Russia, then being eaten by many reindeer, 70,000 of which had to be killed so their contaminated meat would not harm people. Scientists used the tainted lichens to map out the most likely locations of contaminated reindeer. 12-1 Atmosphere (see fig 12-2)
atmosphere is a very thin skin around Earth – 75-80% of it is found nr Earth surface – within 11 miles of sea level at equator and within 5 miles of SL at the poles. This layer is known as the “troposphere”, consists mostly of Nitrogen (78%) and Oxygen (21%), the 2 main constituents of “air”. Top of this layer know as “tropopause” (think: tropo “end”) Next layer above this is the “stratosphere”. Stratosphere has the main defense against UV radiation, ozone (see Fig 12-3)
Layer blocks 95% of UV from reaching the surface of the Earth. Miller notes that man may be decreasing the amount of helpful stratospheric ozone and increasing harmful tropospheric ozone.
12-2 Outdoor air pollution
major types & sources
air pollution not new….stories of “smog” (smoke and fog) go back to beginning of industrial revolution Fig 12-4 shows how Miller lumps both natural and anthropogenic sources together as “pollutants” and also shows how these primary pollutants can lead to secondary pollutants. Miller notes that most air pollution problems are around cities, with high concentrations of sources such as cars and factories. W.H.O. estimates 1.1 billion people live in urban areas where air is unsafe, primarily in developing countries that have poor air pollution regulations. 12-3 Photochemical and industrial smog
photochemical “brown air” smog – caused by rxn of pollutants and sunlight, dominated by “photochemical ozone”. Unburned HCs and NOx begin to rise with morning rush hour, react with sunlight, and begin to produce smog. This builds up through the course of a sunny day, and can reach dangerous levels in afternoon. (we’ve seen “ozone alert” days in the summer in the NYC area….) Worst conditions are in sunny cities with dry climates and lots of cars….LA, Denver, Salt Lake City; Sydney, Mexico City industrial “grey air smog”
more common in US and Europe 50 years ago, when coal and heating oil were more widely used to power industry industrial smog consists of SO2, droplets of sulfuric acid, and a variety of aerosols
this type of smog is still a problem in China, India, Ukraine, eastern Europe
12-4 regional outdoor air pollution due to acid deposition
tall smokestacks emit SO2, NOx, and suspended particulate matter (Fig 12-6) above the “inversion layer”, which keeps them from getting trapped locally, which is good for the local area but these pollutants then travel downwind, causing more “regional” pollution problems plus, these pollutants give rise to secondary pollutants as they travel downwind:
nitric acid, sulfuric acid, and sulfate particles ultimately, these come back down to Earth, hundreds of miles from the source, often as “acid rain” where is acid rain a problem?
Quite a problem in eastern US & industrial areas in Europe & Asia
(red areas in Fig 12-9)
In general, coal-burning power plants are culprits, along with some cars, factories, etc….these generate SO2 which combines with H2O to produce H2SO4. Problems occur downwind from the sources, not necessarily at the sources. Example: power plants in Ohio River Valley (PA, OH) generate pollution which winds up in NE US. Striking stats:
typical precip in the NE US has pH of 4.6, 10x more acidic than normal rainwater with pH=5.6
some mountaintop areas downwind of sources in both West US and East US are “bathed” in acidic fogs and dews with pH down to 2.3 (= lemon juice), 1000x more acidic than normal rainwater….
Miller notes that “worst acid deposition is in Asia”, especially in China, “which gets 73% of its energy from burning coal.
Acid rain effects on human health, etc.
Contributes to respiratory disease
Can leach harmful metals (Pb, Cu) from pipes into water
Damages statues, buildings, cars
Acid rain effects on aquatic ecosystems (see Fig 12-10)
Lose ALL fish if pH drops below 4.5
Aluminum ions are released from soil, carried into lakes, can clog fish gills
Mercury buildup in fish, can affect humans (kidneys, brain)
Note that acid rain can be buffered by limestone, which reduces acidity, but in areas without limestone acidity remains high Miller cites stats showing lakes being seriously threatened:
Many lakes in Norway & Sweden have few fish
Many lakes in Canada are losing fish
Many lakes in US “threatened with excess acidity”
Acid rain effects upon plants and soil
Tree leaves, needles damaged
Important nutrients (Ca, Mg) leached, reducing plant productivity
Aluminum ions are mobilized, reduce plant productivity
Lead, cadmium, mercury are mobilized, reduce plant productivity
Plants weakened and become susceptible to other disease
Mountaintop forests particularly vulnerable, both due to acid exposure and to lack of buffering capacity by thin soil cover
Possible solutions to acid rain Best approach is prevention, rather than cleanup or mitigation. (Fig 12-12)
Primarily, prevention involves use of fuels that do NOT generate
Or, at least cleaning up emissions at the source. Miller points out some very real political problems in assigning responsibility and solving problems, in part because there are large distances separating source from the affected areas. Example:
sources may be in different states and/or countries than the actual affected areas. 12-5 Indoor Air Pollution
Types and sources shown in Fig 12-13
Levels of 11 “common” pollutants are generally 2-5x higher inside homes than outside….
Levels of fine particulates generally higher indoors
“pollution levels inside cars in traffic-clogged US urban areas can be up to 18x higher than those outside the vehicles”
indoor air pollution has been ID’d by EPA and by leading scientists as a very high cancer risk for example, 3000 cases of cancer/year in US may be caused by indoor pollutants , the three most dangerous ones being:
radon gas (perhaps the 2nd leading cause of lung cancer, after smoking…but NOTE – most of these supposedly radon-related deaths occur among smokers or former smokers)
Miller also points out that these radon death estimates are extrapolated to apply to normal homeowners, but this is from data taken from uranium miners who are exposed to extremely high levels of radon. A number of scientists question the validity of this practice.
12-6 effects of air pollution on organisms
our respiratory system is designed to help protect us from harm:
mucus in lung
sneeze and cough
cilia (hairs in upper resp tract)
However, exposure to smoke and other pollutants can “break down” natural defenses, and some horrible diseases can take hold:
12-7 Preventing and Reducing Air Pollution
Important laws passed in 1970, 1977, 1990. there are maximum allowable levels set for certain pollutants. Miller cites sets of “good news, bad news” Good news:
Emissions of 6 criteria pollutants (Table 12-2) declined 31% from 1970 to 1998
Concentrations of 6 criteria pollutants in troposphere have decreased
Lead down 97%
CO down 60%
SO2 down 58%
Ground-level O3 down 30%
PM-10 down 25%
NO2 down 2%
Clean Air Act estimated to have “prevented 1.6 million premature deaths and 300 million cases of respiratory disease”
From 1970 to 1998, emissions of NOx increased 11%
As of 1999, 62 million people were living in 130 areas in US that did not meet the “primary standards for one or more of the 6 criteria pollutants
Half of Americans living in areas with “dangerously” high smog levels
2-cycle jet ski creates more pollution in ONE HOUR than the avg US car does in ONE YEAR
100-hp marine engine (outboard?) creates more pollution in 7 HOURS than a new car does in 100,000 MILES
spills from 14 million small marine engines each year are15x greater than the Exxon Valdez oil spill in 1989
How about using the market place to reduce pollution?
Clean Air Act of 1990 allows an emission trading policy for the worst 110 power plants in 21 states (Midwest and East) to buy and sell SO2 polluting rights.
There apparently are pros and cons to this approach – could allow utilities with old, dirty powerplants to “buy their way out” of cleaning things up. On brighter side, emissions of SO2 dropped by 30% between 1994 and 1997, so SOMETHING good is happening by following this approach. How reduce outdoor air pollution? Fig 12-17 clearly shows that the key is reduction of coal-burning factories and power plants, or at least greatly reduce the burning of high-sulfur coal.
In addition, need to reduce NOx and fine particulate emissions. Another very important key….need to get older vehicles OFF THE ROAD (sorry, kids…..) Why? – Because just 10% of all vehicles in US are creating 50-70% of auto pollution. Globally, developed countries are cleaning up their urban areas thanks to new technology & clean-air policies. Unfortunately, developing countries have urban areas with major air pollution problems and they are getting worse….. Miller finishes off chapter by noting that, at least in US, indoor air pollution poses a greater health risk for most people than outdoor, but $500 million/yr goes to outdoor while only $13 million/yr goes to indoor. He argues for an integrated approach to protecting the atmosphere Good quote at end:
“turning the corner on air pollution requires moving beyond patchwork, end-of-pipe approaches to confront pollution at its sources. This will mean reorienting energy, transportation, and industrial structures toward prevention. Hilary F. French