Tuesday Sept. 1, 2009
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A couple of songs from the Fleet Foxes (Mykonos and Tiger Mountain Peasant Song; White Winter Hymnal is also very nice) to get things started today in NATS 101.  They have a sort of medieval sound that I like especially in a large room with a good sound system like ILC 140.  And I guess you weren't lying to me, some of you also like the Fleet Foxes.

The big event over the weekend was, of course, the unveiling of the Tiki on 4th Ave.


Tiki unveiled!
From the Arizona Daily Star Monday Aug. 31
Taken 08/29/09 by Joel Smith on 4th Avenue at the Tiki unveiling.

I played "Punish the Monkey" from Mark Knopfler in the MWF section because it has a surf guitar sound to it that seemed to fit in well with the Saturday night celebration.

The big event this coming weekend might be some rain (don't get too optimistic given what has transpired so far this summer).  There's a strong hurricane (Hurricane Jimena) located near the tip of Baja California that is forecast to move in our direction.  That might bring in some moisture and an increase in thunderstorm activity.  There is also a football game this coming weekend.  I've observed that if often rains on the first football game of the season.  You can obtain the latest information on Hurricane Jimena and see the predicted path at the National Hurricane Center webpage.

A few more sets of Experiment #1 materials were handed out in class today.  Thursday will probably be your last opportunity to pick up materials.

We finished up the discussion on carbon monoxide that we started last Thursday.  The following figure is from the bottom of p. 7 in the photocopied ClassNotes.


Point 3 explains that CO is produced by incomplete combustion of fossil fuel (insufficient oxygen).  Complete combustion would produce carbon dioxide, CO2.   Cars and trucks produce much of the CO in the atmosphere.

Point 4: Vehicles must now be fitted with a catalytic converter that will change CO into CO2 (and also NO into N2 and O2 and hydrocarbons into H2O and CO2).  In Pima County vehicles must also pass an emissions test every year and special formulations of gasoline (oxygenated fuels) are used during the winter months to try to reduce CO emissions. 

In the atmosphere CO concentrations peak on winter mornings (Point 5).  Surface temperature inversion layers form on long winter nights when the sky is clear and winds are calm.  The ground cools quickly and becomes colder than the air above.  Air in contact with the cold ground ends up colder than air above.  Air temperature increases with increasing altitude in a temperature inversion layer and this produces a very stable (stagnant, there are no up or down air motions) layer of air at ground level.  A very reasonable wintertime morning temperature profile in Tucson is shown at the top of p. 9 in the photocopied Classnotes.


Temperature increases from 47o F at the ground (Point A) to about 60o F at 1000 feet altitude (Point B), that's the stable inversion layer.  Temperature begins to decrease with increasing altitude above Point B.

There is very little vertical mixing in a stable air layer.



When CO is emitted into the thin stable layer (left figure above), the CO remains in the layer and doesn't mix with cleaner air above.  CO concentrations build.

In the afternoon, the ground warms, and the atmosphere becomes more unstable.  CO emitted into air at the surface mixes with cleaner air above.  The CO concentrations are effectively diluted.

Thunderstorms contain strong up (updraft) and down (downdraft) air motions.  Thunderstorms are a sure indication of unstable atmospheric conditions.  When the downdraft winds hit the ground they spread out horizontally.  These surface winds can sometimes reach 100 MPH, stronger than many tornadoes.  An unusually strong and narrow thunderstorm downdraft is called a microburst.


This is page 8 in the photocopied ClassNotes.  Six main air pollutants are listed at the top of this page.  Concentrations of some or all of these pollutants are monitored daily in many cities.  The atmospheric concentration of lead has decreased significantly since the introduction of unleaded gasoline.  PM stands for particulate matter.  These small particles are invisible, remain suspended in the air, and may be made of harmful materials. We'll talk about them in a little more detail on Thursday.

CO, O3 and particulate matter are the pollutants of most concern in Tucson and pollutant concentrations are reported in the newspaper or on television using the Air Quality Index (formerly the pollutant standards index).  This is basically the measured value divided by the allowed value multiplied by 100%.  It's like a quiz grade: your grade is 100% times the ratio of the number of points earned divided by the number of points possible.  With the AQI, the lower the percentage the better.  With a quiz, of course, you want as high a grade as possible.

For carbon monoxide, concentrations up to 35 ppm (parts per million) for a 1 hour period and 9 ppm for an 8 hour period are allowed.   Current Air Quality Index values for Tucson are available online.

Here's another figure from page 9 in the ClassNotes.  It is a plot of monthly average ozone and carbon monoxide AQI values during the year in Tucson (in 1993).


There are a couple of things to note in this figure.  First the highest AQI values for carbon monoxide are observed in the winter.  CO is a winter morning pollutant.  The highest ozone AQI values are observed in the summer.  Ozone, it turns out, is a summer afternoon pollutant (we'll learn why next week).  Both the CO and O3 values remained below 100%, though there are some people that think an ozone AQI of 70 is high enough to present a risk to people with existing lung disease.

So are we have been talking about carbon monoxide found in the atmosphere.  Carbon monoxide is also a serious hazard indoors where is can build to much higher levels than would ever be found outdoors.  You may remember having heard about an incident at the beginning of the school year in 2007.  Carbon monoxide from a malfunctioning hot water heater sickened 23 Virginia Tech students in an apartment complex.  The CO concentration is thought to have reached 500 ppm.  You can get an idea of what kinds of health effects concentrations this high could cause from the figure below (from p. 9 in the photocopied Classnotes).

To get an idea of what effects 500 pm CO concentrations could cause, we will follow the 400 ppm line (shaded orange) from left to right.  At exposure times less than 1 hour you should experience no symptoms.  Beginning at 1 hour you might experience headache, fatique, and dizziness.  Exposures of a few hours will produce throbbing headache, nausea, convulsions, and collapse.  The 400 ppm trace level approaches the level where CO would cause coma and death.  At Virginia Tech several students were found unconscious and one or two had stopped breathing.

Carbon monoxide alarms are relatively inexpensive and readily available at any hardware store.  They will monitor CO concentrations indoors and warn you when concentrations reach hazardous levels. Indoors CO is produced by gas furnaces and water heaters that are either operating improperly or aren't being adequately vented to the outdoors.  A few hundred people are killed indoors by carbon monoxide every year in the United States.  You can learn more about carbon monoxide hazards and risk prevention at the Consumer Product Safety Commission web page.

I have a bad habit of "beating some concepts to death."  Here's an example.  This rather busy and confusing picture just illustrates how small changes in how air temperature changes with increasing altitude can determine whether the atmosphere will be stable or unstable.   Just for the purposes of illustration imagine riding a bicycle north from Swan and River Rd up the hill to Swan and Sunrise (fhe figure shows an elevation change of 1000 ft, it is actually quite a bit less than that).  We didn't go over this figure in class.


At far left the air temperature goes from 47o F to 41o F, a drop of 6o F.  This is a fairly rapid rate of decrease with increasing altitude and would make the atmosphere absolutely unstable.  The atmosphere wouldn't remain this way.  Air at the ground would rise, air higher up would sink, and the temperature profile would change.  In some ways it would be like trying to pour vinegar on top of oil in a glass.  The lower density oil would rise because it would "want" to float on top of the higher density vinegar.

The next picture shows air temperature decreasing a little more slowly with increasing altitude.  This small change makes the atmosphere conditionally unstable (we won't go into what the conditions might be).  The atmosphere is frequently in this state. 

The atmosphere cools only 2o F in the next picture.  This creates an absolutely stable atmosphere.  Air at the ground will remain at the ground and won't rise and mix with air higher up.  Compare this with the glass containing vinegar and a layer of oil on top.  The two layers won't mix.

Air temperature in the last figure actually increases with increasing altitude.  This is a temperature inversion and is very common on winter mornings.  The atmosphere is extremely stable under these conditions. 

Temperature inversions are something you can check out for yourself: head north on Swan Rd. on your bicycle early some winter morning.  You will pass through some pretty cold air as you cross the Rillito River.  By the time you get to Sunrise, the air can be 10 to 15 degrees warmer and will seem balmy compared to the cold air at the bottom of the hill.  If you're up for a real hill-climbing challenge continue north on Swan past Skyline.  You'll find a short but very steep section of road at the far north end of Swan.
Next we moved on to the 2nd air pollutant that we will be discussing - sulfur dioxide.  Here's some basic information from the left hand of p. 11 in the photocopied ClassNotes.

Sulfur dioxide is produced by the combustion of sulfur containing fuels such as coal.  Combustion of fuel also produces carbon dioxide and carbon monoxide.  People probably first became aware of sulfur dioxide because it has an unpleasant smell.  Carbon dioxide and carbon monoxide are odorless.  That is why sulfur dioxide was the first pollutant people became aware of.

Volcanoes are a natural source of sulfur dioxide.



The Great London smog is still one of the two or three deadliest air pollution events in history.
Because the atmosphere was stable, SO2 emitted into air at ground level couldn't mix with cleaner air above. 
The SO2 concentration was able to build to dangerous levels. 
4000 people died during this 4 or 5 day period. 
As many as 8000 additional people died in the following weeks and months. 
Some of the photographs below come from articles published in 2002 on the 50th anniversary of the event. 



from:
http://news.bbc.co.uk/1/hi/uk/2542315.stm

from:
http://news.bbc.co.uk/1/hi/health/2545747.stm

from:
http://news.bbc.co.uk/1/hi/england/2543875.stm

from:
http://www.npr.org/templates/story/story.php?storyId=873954

The sulfur dioxide didn't kill people directly.   
The SO2 aggravated an existing condition of some kind and hastened their death. 
The SO2 probably also made people susceptible to bacterial infections such as pneumonia.
This link discusses the event and its health effects in more detail.

London type smog which contains sulfur dioxide and is most common during the winter is very different from photochemical or Los Angeles type smog.  Los Angeles type smog contains ozone and is most common in the summer.

 Some other air pollution disasters also involved high SO2 concentrations. 
One of the deadliest events in the US occurred in 1948 in Donora, Pennsylvania.



"This eerie photograph was taken at noon on Oct. 29, 1948 in Donora, PA as deadly smog enveloped the town. 20 people were asphyxiated and more than 7,000 became seriously ill during this horrible event."
from: http://oceanservice.noaa.gov/education/kits/pollution/02history.html



from: http://www.eoearth.org/article/Donora,_Pennsylvania

"When Smoke Ran Like Water," a book about air pollution is among the books that you can check out, read, and report on to fulfill part of the writing requirements in this class (instead of doing an experiment report).  The author, Devra Davis, lived in Donora Pennsylvania at the time of the 1948 air pollution episode.
Sulfur dioxide is one of the pollutants that can react with water in clouds to form acid rain (some of the oxides of nitrogen can react with water to form nitric acid).  The formation and effects of acid rain are discussed on p. 12 in the photocopied Class Notes.



Note that clean unpolluted rain has a pH less than 7 and is slightly acidic.  This is because the rain contains dissolved carbon dioxide gas.  We saw how this happens in a class demonstration. Acid rain is often a problem in regions that are 100s even 1000s of miles from the source of that sulfur dioxide that forms the acid rain.  Acid rain in Scandinavia came from industrialized areas in other parts of Europe.


Some of the problems associated with acid rain.

Finally we performed a sort of acid rain demonstration.  The demonstration gives you an idea of how gases can dissolve in water and turn the water acidic.