The first of the topics covered in our Environmental Science section
will be ozone. Now, there are many places to find information
on the beneficial stratospheric ozone, or lack there of, so we
are not going to focus in that layer of the atmosphere. Instead,
our focus will be upon of the factor influencing destructive ozone
concentrations in the troposphere. So here is the report:
A environmental topic that is currently being heatedly discussed is ozone (O3) in the stratosphere or troposphere. In either location, ozone is a highly reactive gas. This means that it will decompose by reacting with certain other substances over a short period of time.
Of the two locations in the atmosphere where ozone is located, the most widely discussed is the place where ozone resides naturally- in the stratosphere. This ozone protects the people on Earth from harmful ultra-violet radiation. It is the beneficial stratospheric ozone that is being destroyed over the South Pole by harmful chemical compounds such as CFCs and carbon monoxide.
The ozone that we chose to investigate is the ozone which resides in the troposphere where it is a danger to humans, plants and animals. This tropospheric ozone is one of the main harmful ingredients in smog.
The most prevalent cause of ground-level ozone is nitrogen oxides released in car exhaust. Other causes include pollutants emitted by industrial smokestacks, utility plants, metal smelters and burning wood. If not for human activities, there would be almost no ozone content in the troposphere. The only natural cause of tropospheric ozone is lightning. This changes O2 into O3.
Though present only in a very small amount, this ground-level
ozone can cause many problems. This ozone can severely damage
crops. For example, a recent study showed that raspberries exposed
to ozone at a level of 240 parts per billion produce fifty-two
percent less than the same type exposed to 120 ppb of ozone. Another
effect is on human lungs. Dutch researchers found a decrease in
bicyclists' lung functions when there was a high ozone content.
This ozone can irritate lung tissue, cause short coughing fits,
and generally reduce the effectiveness of your lungs.
The next step was to formulate a hypothesis
that could be tested. At this time we had found out the way to
make the ozone-testing paper, which would be the vehicle for my
experiment. We now needed to decide where we would test. We knew
that automobiles were a prominent source of ozone, so we wanted
to investigate ozone content on a nearby road. We were also curious
if being inside or outside would affect the ozone content. So
we devised a hypothesis. We thought that the ozone content outside,
near a major road would be higher than the ozone content inside,
away from the road.
Having decided what we were going to test, the next steps were to prepare the paper, find an actual location to test, and implement our plan. This section details what we did, how we did it, and what problems we ran into. The first thing we did was prepare the test paper, or Schoenbein paper. The paper works on the oxidational capabilities of ozone. For this reason, a piece of filter paper is treated with starch and potassium iodide. Ozone in the air will react with the iodide to form iodine. The iodine then reacts with the starch to form a color ranging from light blue to purple. This color varies depending on the amount of ozone present, which makes it well suited for use as an indicator.
Another factor was that the paper became more sensitive to ozone when there was a higher relative humidity. Each day that we performed a test we had to find the relative humidity both inside and outside. We collected data from The Weather Channel for the outside reading, and used a sling psychrometer for the inside data. We took a RH reading when we hung the paper and then again at night, from which we found the average, which is what we used. The chart used to find the amount of ozone works on multiples of ten, so all humidity readings were rounded to the nearest ten.
So we followed the steps and applied the starch and iodide to the paper. Afterwards the paper had to be dried, so we placed it in the microwave as per the directions. The final step was to cut the Schoenbein paper into smaller strips that could be hung for testing.
The Schoenbein paper must be allowed to hang freely in order to obtain the best results, which influenced my decision regarding where to hang the paper. We decided to hang the outdoor paper by a paperclip on my street-sign, which is on Eggert Road. This provides a high access to traffic and the ability to move freely. As for the indoor paper, we decided to hang it on my calendar hook in my room.
Now we were completely prepared to begin testing, which is what we did. There were a few problems that we faced in this project. The first was that we didn't know if the paper would work, or if there would be enough ozone to measure. Fortunately, this fear was assuaged after our first day of testing. Another problem that we had to deal with is that the outside paper would sometimes blow away or fall off the sign. When it blew away, one day of data collecting was rendered useless. Falling is a problem because it limits the air circulation, affecting the amount of ozone detected. The paper fell twice, but was usable once, because the reading was a 10-indicating a full enough exposure.
The most significant factor that determined
when we took readings was the weather. Rain or wet snow will wash
off some of the chemicals, invalidating the reading. We decided
not to hang a paper on days with bad forecasts, leaving only a
few times when the paper was ruined by precipitation. Most of
these days the paper was blown away anyway, so there weren't too
many ruined recovered papers.
This section includes this brief discussion of my results, as well as a data table and a graph. Throughout the duration of my testing I found the same general patterns. Every day that I tested, there was no measurable quantity of ozone inside my house. Outside the results were more varied. Even though they fluctuated, all of the outside readings were fairly high.
To find the ozone content, I needed the Average Relative Humidity and the Schoenbein number. The Schoenbein Number is easily determined using the using the Schoenbein Color Chart and a piece of exposed paper. With the number and humidity, the Relative Humidity Schoenbein Chart will show how much ozone was present. This number is in ppb, or parts per billion. This means that out of every billion molecules, there is that many ozone molecules.
This final section will tell why we think we found what we did, and any conclusions that we can draw from our study of tropospheric ozone. The first thing to be explained is the data. One anomaly is the fluctuation of the outside ozone content. The first thing we thought of was that weekday traffic would be greater (and produce more ozone) than weekend traffic. This doesn't hold true because some of my smallest readings occurred on weekdays. The hypothesis that we currently believe is that on certain days there will be more ozone-producing traffic than others.
Another factor that WE think affects it is the wind. More wind will blow the ozone farther from the road. Studying wind speed versus ozone would be worthy of attention in the future.
There are a few other studies that might follow this one. First, you could study ozone near the road versus ozone outside away from the road, finding distance's affect on ozone content. Secondly, you could study ozone content inside versus outside away from a road, singling out how being inside or outside affects the ozone content.
There are also some conclusions to be drawn
from this project. First, the repeated complete lack of ozone
inside leads me to believe that there is no measurable quantity
of ozone in my room, which is an example of a common indoor environment.
Next, the outside readings show that there is a good amount of
ozone produced near Eggert Road. Finally, my original hypothesis
holds true-there is much more ozone outside near a road than inside
away from a road.
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