My first Publication 1926874721_Alumni_Magazine_June_2010 | Page 10

Issue 3, June 2010
An Example of the Science Fair Projects from the Latest Competition:
Investigation on the Ozone Level in Different Parts of Sofia
(Abridged)
by Pavel Kounov (10/4)
Advisor: Ms. Dima Trendafilova
M ain indicators characterizing the air quality on the surface of the earth are the levels
of sulfur dioxide (SO 2 ), nitrogen oxides (NO, NO 2 , N 2 O, etc.), lead (Pb), nickel (Ni),
cadmium (Cd), arsenic (As) and ozone (O 3 ). The aim of my research work was to
investigate the ozone level in the air of different parts of Sofia, to see where Sofia’s
citizens are exposed to the unhealthiest level of ozone in the air and where the level
of ozone is the lowest. My investigation was done in 14 different areas of Sofia and
was repeated 3 times - during the day (working day), during the night and during the
weekend, to find the mean value of ozone pollution in each region. Strips dipped in KI
and corn starch were used.
Ozone is a colorless odorless gas which is confessed form of oxygen with three atoms
to molecule. Ozone has a number of functions that are healthy and helpful to people.
The ozone layer in the upper atmosphere filters potentially damaging ultraviolet light
from reaching the Earth’s surface. Ozone is also used for water treatment. There are
even small ozone washing machines used to sterilize food or dishes. Ozone is also used
for killing mildew in bathrooms. Hotels use ozone generators to reduce cigarette smoke.
However, ground-level ozone is an air pollutant with harmful effects on the respiratory
systems. Ozone is ready to react with everything and when it comes in contact with
living tissues like our lungs it can cause damages and illnesses. Cars and trucks, gas
stations and factories put the ingredients for ozone into the air every day. In a new
18-year nationwide research of Dr George Thurston, a professor in the Department
of Environmental Medicine at New York University School of Medicine (NYU) was
found that long term exposure to high levels of ground ozone is linked to poor health. A
high-ozone day, for instance, is linked to an increased risk of acute health problems the
next day, such as more asthma and heart attacks. Towns and cities where more people
owning cars live or where there are more industrial plants – have a higher potential for
ozone formation. Another factor causing higher levels of ozone is sunny days with little
wind, since sunlight and heat are engines that drive ozone formation. On a clear day,
ozone level can rise all day long and then decrease after sunset. During nights the level
of ozone in the air drops significantly. Areas near parks and forests are considered less
polluted because of the fact that trees and plants clean the air.
Table 1: Showing the distribution of ozone levels in healthy/unhealthy groups:
Air Quality
Index Values in
µg/m 3 Air Quality Descriptor Health Effects
0 to 50 Good
51 to 100 Moderate
101 to 150 Unhealthy for sensitive
groups (children, elder
people, etc.)
151 - 200 Unhealthy
201 – 300 or more Very Unhealthy
No health effects are expected.
Unusually sensitive individuals may
experience respiratory effects from
prolonged outdoor exertion.
Member of sensitive group may
experience respiratory symptoms
(coughing, pains when taking a deep
breath).
Member of sensitive group have
higher chance of experiencing
respiratory symptoms (aggravated
cough or pain), and reduced lung
function.
Members of sensitive groups
experience increasingly severe
respiratory symptoms and impaired
breathing.
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I presumed that areas near parks
and Vitosha Mountain such as the
American College of Sofia’ campus and
neighborhoods near parks, will be less
polluted by ozone than urbanized areas
like the centre and neighborhoods such
as Drujba, because areas around forests
and parks are surrounded by cleaner
air as a result of the cleaning effect of
the trees in them, while urbanized areas
are overpopulated by cars and objects
increasing the ozone in the air.
To calculate the level of ozone in the air
I used the following equations:
1. 2KI + H 2 O + O 3 =2KOH + O 2 + I 2
2. KI + H 2 O = K + + I –
3. I – + I 2 = I 3–
4. I 3 – + Amylose = Triiodide/Amylose complex
The first one shows how potassium
iodide (KI) reacts with ozone (O 3 ) in the
presence of water (H 2 O) to form three
compounds. The one that is the most
essential is the iodine (I 2 ) in its pure form.
However, the moisture in the air causes
a breakdown of potassium iodide (KI)
into K + and I - . Combining this negatively
charged iodide ion with the iodine, we
get triiodide ion (see equation #3). The
triiodide ion combined with the corn
starch component – amylose, forms
triiodide/amylose complex, which
changes its color when it is exposed
to ozone in the air. Then this color is
compared to the Schonbein Number
Table. Moreover, the average humidity
in the air in the same day is taken into
consideration. The average humidity is
calculated by adding all the values given
by the Ministry for the different hours
of the day and then divided by the total
number of these values.