Tip:
Highlight text to annotate it
X
This lecture is Part Four
of Chapter One: The Air We Breathe
in Chemistry in Context, Seventh Edition.
This letter will cover sources of air pollution,
ozone as a pollutant,
and sources of air pollution indoors.
There're two major sources of air pollution:
combustion from coal plants and combustion from vehicles.
Let's take a look at coal plants first.
So here we have a typical setup
for a coal
fired power plant.
We've got a conveyor
which brings the coal into the plant
sends it into a furnace.
The furnace burns the coal
the heat generated from that burning,
heats water
w hich converts the water to steam.
Steam goes into a turbine
spinning the turbine, and thereby generating electricity.
Which can then be sent out to the community.
The problem with coal
is that it contains impurities.
It's mostly carbon
but there is the impurity of sulfur.
The other major source of air pollution
is combustion vehicles.
The picture on the left here of course
is exhaust coming out of a car.
On the right we have an electric vehicle
which doesn't emit exhaust
but you have to think, "Where is that electricity coming from?"
If that electricity is coming from a coal fired plant,
it's not that much better than a combustion
car.
However one advantage is at least if it is
if the energy is generated in a single place,
we may be able to
treat any pollution
a little more affectively
versus having many different
cars on the road that are emitting exhaust.
There's also sulfur contaminants in gas.
So these sulfur gases can also be emitted
in car exhaustion.
can also be emitted
Sulfur
containing gases
can also be emitted in car exhaust.
So if you had to look at some kind of
chemical formula
coal which is mostly carbon but has some sulfur plus oxygen
can form sulfur dioxide.
Sulfur dioxide can further react with oxygen
to form sulfur trioxide.
Here we have the space filling model of that reaction:
two SO2 molecules,
one 02 molecules,
forming two SO3 molecules.
We can see we have 1,2,3,4,5,6
red spheres on our reactants.
Representing oxygen atoms and we have six
on our products, so this is a balanced equation.
So, these sulfur dioxide and sulfur trioxide molecules
are problematic because what happens is they dissolve
in water
in the atmosphere.
and when they do, they form this H2SO4 molecule
which is known as sulfuric acid.
And a bit later on I'll talk about Nitric acid forming as well.
And so from cars and from smokestacks,
these sulfur containing
and nitrogen containing
molecules
then form acid
in the atmosphere, and that can then rain down upon the earth.
We have been working hard to remove our
our sulfur from fuels,
a diesel fuel typically had much more sulfur than it does now.
Also industrially in coal plants,
we're taking a lot of steps
to reduce that is well.
You might've heard of smokestack scrubbers
basically large filters they could put on a smokestack
to help reduce those emissions.
NOX, is another
general term for pollution
molecules that contain nitrogen and oxygen.
They are what gives smog its brownish tinge,
and this type of combustion
reaction occurs.
We've seen this
previously this nitrogen gas plus oxygen gas
can form this nitrogen monoxide.
Here we have the space filling model and really
this is a simplified version of the chemistry that occurs.
There are actually a few more steps in the process
but overall this is what will occur.
Once you form that nitrogen monoxide it can then
go on to form nitrogen dioxide
and even nitrogen trioxide.
So that's why these
molecules as a whole are referred to NOX
where that X can be a one in the case of
nitrogen monoxide or two in the case of nitrogen dioxide.
but all of them are problematic in,
when they reach a certain concentration in the atmosphere.
So they're respiratory irritants
first of all,
they're also, which is even maybe a bigger problem,
they're a precursor to ozone formation.
And we're not talking about the good ozone formation.
We're talking about ozone formation
right above the surface of the earth.
Not the ozone layer in the stratosphere.
Then of course they also can make acid rain,
as I mentioned earlier.
You take some of the NOX, nitrogen monoxide nitrogen dioxide
dissolve it up in some water
up in the clouds above us
and yay! We get nitric acid.
Yay, strong acid and then nitrous acts acid.
Yay I like acid rain, it tingles.
Is this equation balanced?
Well, hopefully you've had a second to think about that.
What I like to start with is,
elements that popped out, now there are, at me.
There are a lot of oxygen and hydrogen atoms here.
Not many nitrogens so I'm going to check the nitrogens.
First, I see two nitrogen atoms.
Two nitrogen atoms.
So far that looks good.
I see one, two hydrogens, one, two hydgrogens
that looks good.
3 + 2 oxygens
1, 2, 3, 4 oxygens.
Ehhhh. It is not balanced.
Ok, that was just to practice.
We're not going to actually balance this equation
right now.
Carbon monoxide, we talked about
earlier in the chapter.
It's also formed in combustion in engines.
It is monitored by most state
DMV testing facilities.
And if your car is working very well,
the majority of the combustion
will be what is called complete combustion.
Your gasoline, your mixture of hydrocarbons,
hexanes, heptanes, octanes, nonanes will undergo combustion
produce CO2 and water.
Which is we don't really want a lot of CO2 in the atmosphere
but this is actually indicative of a complete combustion.
Which is better than an incomplete combustion,
where we have our same reactants but this time
we're forming carbon monoxide and other
volatile organic compounds, that's what VOC stands for.
Catalytic converters are in the vehicles to help remove
some of that uncombusted or the incomplete combustion products.
They'll also help convert carbon monoxide to carbon dioxide
So basically it's a,
it acts as a place where unreacted
gasoline compounds
will get broken down further or reacted to form carbon dioxide.
So these volatile organic compounds,
they're, it's just a very general term.
It's anything that is carbon based,
that evaporates at room temperature.
So
this is formed alongside carbon monoxide
during incomplete combustion
but it's also in a lot of household products.
and we'll talk later about,
a little bit, in a moment about ozone formation.
But even in your paints if
you are concerned about indoor pollution
you probably want to be looking for VOC
free paints.
Here's a little paint can and if we
zoom in on it there it says, "zero volatile organic compounds."
That means you're not going to have these organic molecules
gassing, off gassing,
from your paint as it dries.
Which is just going to lower the level of indoor pollutants
that can cause irritation or
or other problems,
potentially cancerous
for long-term exposure.
Sometimes those volatile organic compounds can also play a role
in changing the composition of NOX
so converting more nitrogen monoxide to nitrogen dioxide.
It's somewhat of a complicated reaction but
the VOC's interact with hyrdoxal radicals
that in order, that need to be present for this to occur
to produce more nitrogen dioxide.
And we'll see in a moment how
volatile organic compounds also play a role in ozone
breakdown in formation.
So ozone here, these
three spheres represent ozone
the ozone molecule.
This reaction, the formation of ozone
at the surface of the earth,
again in the troposphere not where we want it in the stratosphere,
is catalyzed by sunlight.
So we have NOX or nitrogen monoxide, dioxide, what have you,
plus sun light
will cause the formation
of an oxygen radical.
That's what the little asterisks means here.
Which then reacts with oxygen gas to form ozone, O3.
and again we don't want that forming
down here close to the surface and the troposphere.
Volatile organic compounds can also, with sunlight,
form ozone as well.
Now there's a short clip on the formation of ozone which
is a nice little animation here.
So just to summarize
NOX and volatile organic compounds
heat and sunlight
form ozone.
So this is particularly true in places like
Los Angeles that are very sunny.
That don't get a lot of airflow
in the valleys
and all that sunshine in all those pollutants
perfect combination for smoggy ozone filled air, unfortunately.
So ozone,
is a lung irritant,
can make your eyes burn.
It also can react with volatile organic
compounds to make other
photochemical smog.
It can cause rubber to crack,
can kill plants.
It's just not something we want in the troposphere.
Ozone in the stratosphere, good.
Ozone in the troposphere,
near the surface of the earth, bad.
Now this relates somewhat to a term
or an expression,
called the "Tragedy of the Commons."
It's when
there is a shared resource that no one is actually responsible for.
Then,
if there are no consequences
to overuse or abuse,
it unfortunately becomes over used and abused by everyone.
So if there's a shared resource like the ozone layer we
Well perhaps,
overfishing is a better example.
You know if someone overfishes up here
They're not as aware of how that may impact other areas.
And so as a community we, global community, we really need to
be aware of any shared resource and how
even if we may not be responsible for it,
how it does impact us as a global community.
Here are some pictures of photochemical smog.
Again it's cities that don't have good
airflow with those NOX and VOC's can build up and then
with sunlight, form our
ozone and other smaller compounds.
And we've made some improvement
with the amount of air pollutants 1970 vs. 1977.
This bar graph here showing the metric tons per year emitted
and you could see carbon monoxide,
this is in the United States, has dropped from 120
metric tons to about 80.
And we're making inroads on
sulfur dioxide and volatile organic compounds as well.
This is comparing to 1997
so hopeuflly we've made even more progress.
Unfortunately, it looks like the nitrogen oxides have increased
a little bit.
We've talked about outdoor air pollution but
indoor air pollution can actually be more dangerous.
If you don't have a lot of airflow
particularly if you have a newer house,
that has very good insulation and the window's sealed very well
you can build up concentrations of some of these
chemicals to a much larger degree than you might see outdoors.
So we also combust material inside.
Wood stoves,
any kind of heaters that use a gas,
or perhaps kerosene.
Those molecules, then NOX in the carbon monoxide
and the volatile organics, can build up.
Then of course cigarettes, hopefully you don't smoke indoors.
Even if everybody's a smoker in the house,
you should not be smoking indoors if possible.
Burning candles
do also emit
these compounds.
Candles are petroleum product.
Wax is obtained from crude oil.
As I mentioned earlier,
paint if it's not volatile organic chemical or compound free
will be releasing those VOC's, paint.
Finger nail polish, glues,
dry cleaning, the organic compounds used in dry cleaning,
those will off gas while sitting in your home.
The garage can be a place of high concentrations
of volatile organic chemicals.
If you have a lot of, keep your solvents
and pesticides and other compounds.
As well as when the car is
started in the morning.
If you close the door right away
then those chemicals will stay in there.
And then radon, is the third big one.
Radon is a gas that's naturally radioactive
and naturally bubbles up through the earth's crust.
You can't actually see it bubbling.
And here, this map here, well first let's look
to the left we see radon on the periodic table.
It's a Noble Gas.
So noble gases are supposed to be unreactive.
And it is chemically, but as far as from an nuclear
chemistry perspective,
it's, the atom itself is unstable.
The radon isn't reacting with anything per say.
It's actually splitting apart
into
smaller atoms and when that occurs
very high powered or
radioactive energy
is given off.
And we'll talk more about that in chapter seven.
This map shows the radon distribution in the U.S.
So if you're in one of these blue or green regions,
you need to
make sure you monitor your radon,
particularly if you have a basement.
We live up here in Portland, and only more recently has it
come to the attention that particularly
in North Portland and Northeast Portland there are
some actually high levels of radon
deposits or high levels of radon found in homes.
So if you are in Portland in the North, Northeast Portland
you should have perhaps a radon detector in your basement.
Or have it checked
every so often.
The detectors in the home kits to check
the radon are fairly straightforward.
Unfortunately if you do find
a high concentration of radon
you'll have to install
something to mitigate
the radon.
It basically acts as a,
it absorbs,
the radon.
It'll filter the air and
those costs I think around $1500 so,
I hope you don't find it but if you do have radon
high levels of radon in the home.
It will cause and increase your chances of all sorts of cancers.
So keep that in mind when you're going
to paint a room, burn some incense,
how well is your kitchen ventilated.
All of these are actually can be, again more dangerous
than outdoor air pollutants.
Due to the speed in which
they can build up to a more significant concentration.
Now let's try to conceptualize how many molecules are actually
in a breath when you take in a lung full of air.
You're taking in
about 2 x 10^22 molecules.
this picture here is just
this fellow's testing this young woman's
ability
to take in a breath measuring lung capacity.
But for the average person
This many molecules
zoom into our lungs when we take a breath of air.
Which is a lot.
So think about for a minute,
see if you can calculate
how many of those molecules are nitrogen gas.
Let's assume you're breathing really clean air.
Based on what we learned previously in chapter one,
how many of those molecules are nitrogen gas?
Once you've determined that,
think about for a moment,
what determines how many numbers
we write down after doing a calculation.
Do we write down every single number are calculator spits out?
Ponder these two questions for a moment.
So for the first question,
how many of those molecules are nitrogen gas?
Well,
we know that the atmosphere is roughly 78%
nitrogen gas.
If that's the case we should be able to multiply this number
by
0.78
I added an extra digit here.
That should've been there as well.
But 2.0 x 10^22 molecules x 0.78.
If we take the answer that comes from a calculator,
it ends up being 1.56 x 10^22.
Molecules are nitrogen out of
2 x 10^22.
The majority are nitrogen.
But now
do we write down every single number?
what if I even,
what if for some reason
it gave me an even longer
value like 1.5629?
Would it make sense to write those numbers all,
all of those numbers down?
Well, the rule of thumb
is that you want to stick with
the fewest numbers
given
in the original question.
That's a very general rule of thumb.
But if they only give you two digits here in the data,
or you only know the percentage to two digits
when you're doing multiplication and division
you pretty much want to then keep it to two digits.
Just roughly.
We're not going to go into any more detail than that.
But if you're curious you can go and
on YouTube enter
something called significant figures
and you'll get more information.
This ends the last part of chapter one.
Now that we've completed chapter one
you should be ready to complete the homework for chapter one.