investigating the vertical ozone proﬁle, with a speciﬁc focus ......investigating the vertical...

Investigating the vertical ozone profile, with aspecific focus on the ground level andtropospheric ozone over Bangalore.

Aman Saxena*†, Rahul Tarak‡, Rithvik Mahindra§ and Govind Nair¶

AbstractThe aim of this paper is to establish a vertical ozone profile until the tropopause overthe city of Bangalore during April 2018. The payload was launched to approximately26 km, and the duration of the flight was for around 6.5 hours. The significance of thisissue stems from the impact ozone has on the ecosystem and human health, as it canlead to harmful effects for both. In a country such as India, where development in suchcities has led to a drastic increase in pollution, we felt it was necessary to conduct thisstudy in order to analyze these pollution patterns. Our resulting analysis showed thatthe concentration of ozone in the troposphere far exceeded the values set by both Indianstandards and international standards. Such concentrations have a long-lasting impact onrespiratory function in individuals and the issue is of great importance in Bangalore.

Key words: Ozone profile, troposphere, health effects, weather balloon, data analysis,Bangalore

1 Introduction

1.1 Background information

Understanding how the ozone concentration varies in the atmosphere is essential in under-standing how the Earth maintains and regulates the frequencies of light. The atmosphereis divided into five major layers: the Troposphere, Stratosphere, Mesosphere, Thermo-sphere, and Exosphere. The troposphere comprises 75% of the total mass of the atmo-sphere. The extent of this layer varies geographically, with the highest point being 17-18kilometers above the equator. Ozone present in this layer is called tropospheric ozone.Ground level ozone is ozone present beneath the troposphere. The presence of ozone in

*Corresponding author.†E-mail: [email protected]‡E-mail: [email protected]§E-mail: [email protected]¶E-mail: [email protected]

1

Ozone profile over Bangalore 2

these layers can be attributed to the same reason (the emissions from industrial sectors,motor vehicle exhausts, chemical solvents, along with other sources) and is ecologicallydetrimental. The stratosphere extends from the tropopause (the top of the troposphere).Stratospheric ozone is beneficial due to its ability to absorb UVB radiation, in contrast totropospheric ozone. Levels of tropospheric ozone are steadily increasing, and will lead togreater ecological damage.

Note - The usage of the word tropospheric ozone in the subsequent sections also andmore importantly includes the effects of ground level ozone as well. Both are createdunnaturally due to the same reason, and hence the effects are the same.

1.1.1 Tropospheric ozone formation

Production of hydroxyl radicals [1]

O3 + hv → O(1D) + O2

O(1D) + H2O → 2HO• (1)

Within the troposphere, ozone is photolyzed in the presence of water vapor to form anoxygen radical in the excited state. This oxygen radical then reacts with the water vaporto form hydroxyl radicals.

Ozone production with Carbon Monoxide [1] [2]

HO• + CO → •HOCO (2)

The hydroxyl radical reacts with carbon monoxide to form an intermediate hydro carboxylradical.

•HOCO + O2 → HO•2 + CO2 (3)

The hydro carboxyl radical is highly unstable and reacts with oxygen gas to form carbondioxide and the hydroperoxyl radical.

HO•2 + NO → HO• + NO2 (4)

The reaction between the hydroperoxyl radical and nitric oxide leads to the formation ofnitrogen dioxide and hydroxyl radicals.

NO2 + hv → NO + O(3P) (5)

The nitrogen dioxide is photolyzed to form nitric oxide and an ozone radical.

O(3P) + O2 → O3 (6)

Finally, the ozone radical reacts with oxygen gas, leading to the formation of ozone gas.

CO + 2O2 + hv → CO2 + O3 (7)

The net reaction can be stated to be the reaction between carbon monoxide and oxygen inthe presence of light to form carbon dioxide and ozone gas. In this case, the radicals andnitrogen oxides act as catalysts rather than reactants or products in the net reaction.


Ozone production with Methane [1]

HO• + CH4 → •CH3 + H2O (8)

The hydroxyl radical from equation (2) and other sources react with methane to form themethyl radical and water.

•CH3 + O2 → CH3O•2 (9)

The methyl radical then undergoes a reaction with oxygen gas to create the methylperoxyradical.

CH3O•2 + NO → CH3O

• + NO2 (10)

The methylperoxy radical then reacts with nitric oxide, producing the methoxy radicaland nitrogen dioxide.

CH3O• + O2 → CH2O+ HO•

2 (11)

The methoxy radical reacts with oxygen gas, rapidly forming formaldehyde and the hy-drocarboxyl radical.

HO•2 + NO → HO• + NO2 (12)

As in the previous, the hydrocarboxyl radical is unstable and quickly reacts with nitricoxide and forms the hydroxyl radical and nitrogen dioxide.

NO2 + hv → O(3P) + NO (13)

The nitrogen dioxide is photolyzed to form an oxygen radical and nitric oxide.

O(3P) + O2 → O3 (14)

Finally, oxygen gas reacts with the oxygen radical to form ozone gas.

CH4 + 4O2 + 2hv → CH2O + H2O + 2O3 (15)

The net reaction can be stated to be the reaction between methane and oxygen in thepresence of light, leading to the production of formaldehyde, water and ozone gas. Thenitrogen oxide reactions act as catalysts in this case and are not included in the net reac-tion.

1.1.2 Ecological impact of tropospheric ozone

Tropospheric ozone is known to have harmful effects on the human body, especially acuteand chronic effects relevant to cardiovascular and pulmonary health. According to theNational Ambient Air Quality Standard (NAAQS) established by the Environmental Pro-tection Agency (EPA), the United States ozone standard is 70 ppb (parts per billion). [3]The Indian standard for ozone is 100 ppb (1 hour mean) and 180 ppb (8 hour mean). [4]


Internationally, the ozone standard is set as 100 ppb. [5] As mentioned below, health risksare still present at lower concentrations, but these standards provide a sufficient buffer tobeing potentially fatal.

At an average of 60 ppb, respiratory inflammation can be observed. In the range of60 – 90 ppb, with an average of 70 ppb, decrements in lung function in addition to respi-ratory symptoms can also be observed. Other symptoms shown to develop during short-term exposure to ozone include inhibited lung development, onset asthma, and prematuremortality. [6]

The harmful effects extend to the general ecosystem as well, affecting both animalsand plant life. More than 90% of vegetation damage can potentially be linked to theconcentration of tropospheric ozone. This tropospheric concentration could also lead toreduction of crop yields and forest production by 0 – 30%. This exposure to ozone is onlyrising, and by 2100 it is estimated that 50% of forests will experience ozone levels of over60 ppb. [7] Several other factors such as species diversity, habitat quality, and the waterand nutrient cycles present in an ecosystem are at risk due to an increased presence ofozone concentration. [8]

1.2 Importance of the study

It is of extreme importance that the ozone profile is studied over cities in India, a countrywhich has in recent years experienced a surge in the production of many goods resultingin a highly increased usage of fossil fuels. It is imperative that the effect of these changesupon the Indian environment is further studied, in order to understand the possible impactsof changes in the ozone profile, both in the present and future. By being able to understandthese impacts, it will be possible to make the necessary adjustments to policies so that theenvironment and people of India, as well as the general world population, are protectedfrom the harmful consequences of high concentrations of tropospheric ozone.

The major focus of this study is to investigate the vertical ozone profile over Ban-galore, and how it compares to set standards. Bangalore has been chosen in particularbecause of its extremely fast urbanization, and we hypothesized that it is more susceptibleto higher concentrations of tropospheric ozone. This means that there have likely beendramatic changes in the ozone profile above Bangalore in recent years, due to the reasonsoutlined above. Additionally, there have not been a substantial number of studies aboutthese effects that have taken place in Bangalore, so we felt that it was paramount that thestudy be done in Bangalore, in order to understand, analyze, and communicate these ef-fects while correlating them with trends that establish a relationship between high levelsof tropospheric ozone and its effects on health.

1.3 Literature study

1.3.1 Book: Estimating Mortality Risk Reduction and Economic Benefits fromControlling Ozone Air Pollution

By reviewing the pollutant concentrations in the National Ambient Air Quality Standards(NAAQS), the Environment Pollution Agency (EPA) administrator makes a public-health


policy judgment that addresses mitigation measures aimed to curb the emissions and pub-lishes a cost-benefit analysis on the pollutant (in this case, ozone). The EPA then seeks theNational Research Council (U.S.) to form a committee that looks into epidemiological re-ports to understand the ozone-mortality relation. The committee then concludes its resultsand publishes a report. This book contains the entire report published by the committee in2008. It delves deep into the meaning of the ozone standards and their significance to theenvironment, ozone formation with typical ozone precursors, ozone-exposure modeling,ozone-mortality studies, factors that affect the interpretation of ozone mortality effects,and the overall conclusion and research recommendation for the analysis. It concludesthat short-term exposure to ambient ozone is likely to contribute to premature deaths. [9]

1.3.2 Book: Atmospheric Reaction Chemistry

This book gives an in-depth overview of atmospheric chemistry, fundamental photochem-istry, gas phases, and heterogeneous reaction kinetics. It provides information on chemi-cal reactions that occur in the troposphere and stratosphere, and covers photochemistry oftropospheric ozone, stratospheric ozone depletion, and the stratospheric aerosol layer. [10]

1.3.3 Article: Health effects of tropospheric ozone

The paper discusses the health related effects of tropospheric ozone. Although the re-search paper focuses on studies of the 90s, the impact of ozone on health remains thesame and provides a detailed insight of the manner in which ozone targets the living cellsin the body. [11]

1.3.4 Article: A review of surface ozone background levels and trends

The paper contains literature studies conducted on historical and current surface ozonedata from background stations in Canada, the United States, and Asian countries in theNorthern Hemisphere for the purpose of characterizing background levels and trends,present plausible explanations for observed trends and explore projections of future ozonelevels. The paper shows that an increase in NOX level triggers an increase in the groundlevel or tropospheric ozone levels. [12]

1.3.5 Article: Relation between tropospheric and stratospheric ozone at Thumba(8.5◦N, 77◦E) and Bangalore (13◦N, 77.5◦E), India and its effect on environ-ment

The article explores how yearly variations show an increasing trend in tropospheric ozonebut a decreasing trend in stratospheric ozone from 1979 to 2005. The undesirable environ-mental effects caused by such high tropospheric ozone level and low stratospheric ozonelevel have also been stated. Since the article is with regards to Bangalore, our resultscould be compared with the study to analyze trends. [13]


1.3.6 Article: Significance of volatile organic compounds and oxides of nitrogen onsurface ozone formation at semi-arid tropical urban site, Hyderabad, India

The paper discusses how the levels of volatile organic compounds (VOCs) and nitrogenoxides (NOX ), which are common ozone precursors affect the ozone concentration levelin the Deccan plateau region of Hyderabad, India. The crossover point relationship be-tween NOX , VOCs, and O3 shows an enhancement of O3 at lower levels and a decreaseat higher levels of NOX in the range of VOC concentrations studied. [14]

1.3.7 Research paper turned web page : Ozone detection using visible light and acustom integrating sphere

The study stated in this paper follows a similar goal to that of our mission, which is tomeasure ozone concentration as a function of altitude. This was derived using an MQ-131 gas sensor and a ‘custom integrating sphere’, which consisted of a light sensor andphotodiode that measured the intensity of light absorbed by ozone, and was performed bymeans of a weather balloon. The returned values conformed to known atmospheric ozoneconcentrations, up until twenty-seven kilometers. [15]

1.3.8 Article: Vertical distribution of ozone and VOCs in the low boundary layerof Mexico City

This study involved a tethered balloon system that recorded atmospheric parameters upuntil one kilometer above the Earth’s surface over the period of one day. A radiosondewas used in the study, and other variables such as temperature and density were alsomeasured. [16]

2 Methods

The experimental set up consisted of a payload that was launched via two hydrogen filledweather balloons.

2.1 The electrical interface

The payload contained an ozone sensor, a temperature and pressure sensor, an ArduinoUno, an SD card module, a Bluetooth module, a power bank, an I2C shield and a Kingstonindustrial SD card.

The ozone sensor was an MQ131 gas sensor breakout board. The resistance of thesensor varies depending on the concentration of ozone present in its surroundings. Thesensor was calibrated to detect concentrations between 10 ppb and 2000 ppb, as per themanufacturer’s data sheet.

The temperature and pressure sensor was an MS5803-05BA breakout board. It mea-sured temperatures from ranges of -40 ◦C to +80 ◦C, while the pressure sensor measuredvalues from 0 to about 1000 mbar.


FIGURE 1: Schematic of the payload

The Arduino Uno was fitted with an I2C shield due to the lack of necessary I2Cconnections on the general motherboard. The SD card module was connected to thisshield. An industrial card was necessary to withstand the harsh conditions that wouldlead to the deterioration of a normal SD card. Specifically, this card had a lower operatingtemperature than normal (about -60 ◦C), allowing it to operate at colder temperatures, andthermal expansions and contractions did not hinder the performance of the SD card.

The Bluetooth module was integrated into the circuit to make sure that the initializa-tion of the SD card was successful. Despite the low probability of the initialization failing,to reduce the margin of error, the Bluetooth module was programmed to send data valuesto a mobile phone, indicating that the whole system was functioning correctly.

A 11000 mAh power bank was used as the source of power for the payload. The elec-tric potential of any power source decreases drastically when sent into cold temperatures;in order to combat this, a power bank with a very large capacity was used.

In addition to these modules, an accelerometer, a humidity sensor, and a pressuresensor were present in a separate payload launched alongside the primary payload.

2.2 Mechanical and structural interface

The exterior of the payload was entirely composed of 3-inch-thick industrial grade Styro-foam. Several layers of tape were also added to the structure on the interior as well as onthe exterior.

Inside the payload, two compartments were created for the circuity, and the compart-ments were almost completely sealed off from one another. The first compartment wassmaller than the other compartment. The ozone and temperature sensors were taped downin the smaller compartment. Two holes were drilled on opposite ends of the segment, anda funnel was attached to one hole to create a path for air to flow through the payload. Thetwo sensors were placed in such a way that they directly in the air flow. This allowed


them to constantly capture correct data. The breakout board of both of the sensors wasfurther insulated with Kapton tape, and then covered with standard cotton tape. The wiresthat connected the sensors were passed through a small hole on the side to the other com-partment, which contained the remaining components. The hole that enabled the wires togo through was sealed with hot glue. The equipment in the other compartment (the Ar-duino, SD card, Bluetooth module, and power bank) was insulated with Kapton tape, andcovered with cotton tape. The wires were insulated using insulation tape to ensure anyoverheating or short-circuiting did not occur. The power bank was also heavily insulateddue to its tendency to lose electrical potential at colder temperatures.

Both compartments were sealed off from each other because it was necessary that theairflow only interacted with the sensors. Industrial standard sensors were used, as they arebuilt for harsh environmental conditions and lower operating temperatures. The Arduino,I2C shield, and the SD card module were not built to withstand these conditions, andhence extra care was taken to ensure that they were completely insulated.

The smaller compartment also contained a sensor that measured the temperature ofthe environment. In order to differentiate between the temperature of the surroundingenvironment and the internal temperature of the payload, the MS5803-05BA temperaturesensor was placed in the same compartment as the ozone sensor.

2.3 Testing

To assess the operability of the electrical components under the harsh conditions of theatmosphere, testing was done using industrial equipment at SKC labs in Bangalore. Whilethe manufacturers had given assurances of the quality and durability of the sensors, itwas important that they were tested to ensure that they would survive at the extremetemperature conditions.

The entire payload was placed inside a climate chamber; this was a chamber capableof producing temperatures of a minimum value of -40◦ C, which is a lower value thanwhat was expected inside the payload. While the primary reason for testing was to ensurethe electronics could survive the low temperature, it also served to check the insulation ofthe payload by comparing the disparity between the temperature of the chamber and thetemperature of the payload.To conduct this test and simulate the rate of change of temperature in the atmosphere weslowly decreased the temperature values in decrements of -10◦ C which allowed for thecomponents to stabilize their readings. While all electronics except the two sensors werein a separate further insulated compartment, it was of utmost importance to ensure thatthe SD card survived the very cold temperatures and was still able to maintain its writespeed.

Figure 2 shows the data gathered from the temperature chamber itself and representsthe actual temperature within the chamber. Figure 3 shows the data gathered from theoutput of the temperature sensor, which was placed inside the chamber for 1.49 hours(5375.1 seconds). The difference in end times between the sensor’s data and the chamber’sdata can be accounted for by the increased duration for which the sensor was left in thechamber after the machine had been shut off. It is of note that the rates of change of the


values recorded by the temperature sensor and the chamber are very similar. The disparitybetween the temperatures recorded can be attributed to the insulation of the payload.

FIGURE 2: Temperature Test Data Output:- Chamber

FIGURE 3: Temperature Test Data Output:- Sensor

The ozone sensor was chosen to withstand the severe conditions present at higheraltitudes. This sensor’s durability was also put to the test, and it survived the extremelylow temperatures in the climate chamber. The fact that the ozone sensor was successfullyable to write data to the SD card at temperatures as low as -40◦C in the insulated payloadproved that the sensor would be able to survive the mission.

As the manufacturer had given assurances and shown enough cases where the sensorhad performed accurately, we did not extensively test the ozone sensor’s accuracy due tofinancial reasons, instead choosing to perform a few necessary tests to verify the sensorwas working.

2.4 Method of launch

The balloons used for the launch were filled with hydrogen gas, and were launched withtwo modules; the payload, which contained the main experiment, and a communicationmodule with additional sensors. While the payload was managed by our team, the com-munication module was managed by IIA. This communication module contained an ac-celerometer, a pressure sensor, an external temperature sensor, a radio communication


system, and both a primary and secondary cutoff mechanism to burst the balloons threehours after launch. Both cutoff mechanisms failed, and the balloons did not burst at thedesignated time and altitude. During the flight, one of the two balloons prematurely burstafter around 55 minutes of flight. As a result, the ascent rate drastically fell, leading to aseries of events that eventually led to every component of the secondary payload failingafter 2.5 hours. While the balloons were meant to be in flight for a maximum durationof three hours, they ended up flying for nearly six and a half hours. Additionally, themaximum distance of the landing point from the launch point was estimated using soft-ware to be around 100 kilometers. However, the payload was actually found about 250kilometers away from the launch point, in the hills in the countryside. It can be assumedthat the reason for this is that the payload got caught in a horizontal wind stream, forcingit to only travel horizontally.

2.5 Altitude calculations

Due to the secondary payload’s failure after 2.5 hours, it was necessary to approximatethe altitude using statistical analysis of the data received from both payloads. Figure 4shows the ascent rate graph from the time of launch until the failure of the sensor.

FIGURE 4: Ascent Rate from launch

Figure 5 shows the above graph integrated, hence providing the altitude of the payloadfrom launch for 2.5 hours.

FIGURE 5: Altitude from launch


This created a problem, as it was already known that the cutoff mechanisms had failed,and that the duration for which the balloon had flown was longer than expected. Therefore,a calculated approach was taken to approximate the potential final altitude of the graph.

First, the landing time was approximated by looking at the temperature graph, andidentifying the point at which the graph reached the approximate temperature of the bal-loon’s known landing site. A landing time of roughly six hours and twenty-five minuteswas calculated using these approximations.

To get an idea of the maximum possible altitude, it was assumed that the balloon rosefor the entire duration of 6 hours and 25 minutes. The ascent rate graph (Figure 4) wasextrapolated until the approximated landing time, as shown in Figure 6; it was statisticallysignificant in accordance with the decaying pattern at the end of the graph.

FIGURE 6: Extrapolated ascent rate graph

This graph was then integrated to find the maximum possible altitude the ballooncould have achieved. This is seen in Figure 7, and is 28088.061 m.

The specifications of the launch vehicle and the atmospheric conditions on the day oflaunch were considered to approximate the average rate of descent of the balloon as 5.3m/s. This value was integrated over a large time period, in order to make sure that the timeat which the second balloon burst was within the limits that the descent rate is integratedfor.

Figures 7 and 8 were superimposed to create the final approximated altitude vs timegraph. The point of intersection of these two graphs gave an approximate value of thepeak altitude of the balloon to be 25840.415 meters, as seen in Figure 9.

Figure 10 represents the final altitude graph calculated from the above steps. The solidblue line represents the actual altitude, and the dotted lines represent the maximum andminimum possible altitudes. This is due to the assumptions made; to account for possibleinaccuracies, it was important to give a relatively large uncertainty.


FIGURE 7: Maximum altitude graph

FIGURE 8: Integrated descent graph

3 Results

The data collected during the experiment shows the below results:Figure 11 shows the concentration of ozone with respect to time for the whole flight

duration. As expected, the concentration of ozone steadily increased at an exponentialrate for the first two hours. The balloon crossed the troposphere at about an altitude of 18km and passed into the stratosphere, but the ozone peaked at a concentration of 0.4525ppm at a height of 14820.18 m. It maintained an average concentration of around 0.40ppm in the troposphere before entering the stratosphere. The concentrations in the lowerstratosphere, as expected, were lower, which can be seen by the decrease in concentrationshown on the graph. The balloon then started to descend, eventually the entering the sameozone-dense layer in the troposphere that caused the original peak, leading to a secondspike in the graph. The reason for the diminished height and duration of this second spike


FIGURE 9: Altitude intersection graph

FIGURE 10: Final altitude graph

is due to the higher descent velocity and lowest amount of time spent in the region. Uponlanding, the ozone concentration stabilizes at a higher ground level concentration thanfrom the launch point. The landing value is considerably higher than the launch pointvalue of ozone due to the fact that it was nearly daytime, and since the concentration ofozone increases during daytime, it possibly explains the higher concentration. Anotherreason is that the payload landed in a hilly area next to the city, and hence the altitude wasconsiderably higher than the launch point’s altitude.

Figure 12 shows the relation between ozone and altitude. As seen in the figure, theozone level increases for most of the graph, but the rate at which the ozone level increasesalso rose after the balloon reached a height of 12,000 meters. After reaching a peak of0.45 ppm at 19,000 meters, it fell to 0.27 ppm at 21,000 meters, and it continued to riseuntil 0.43 ppm at 22,250 meters. The standards shown in the graph are standards for


FIGURE 11: Ozone vs time

FIGURE 12: Ozone vs altitude

ground level ozone. As the legend indicates, the American standard is 0.075 ppm, theInternational standard is 0.05 ppm (eight hour mean) and the Indian standard is 0.05 ppm(eight hour mean) or 0.09 ppm (1 hour mean).

The average ground level ozone concentration for the first ten kilometers is 0.101ppm. As indicated by the figure, the concentration is higher than that of all three safetystandards, by a large margin. An average concentration of 0.101 ppm translates to an AirQuality Index (AQI) within a range of 151-200, which is considered ’unhealthy’ for thegeneral population. Furthermore, 0.1 ppm is considered the maximum possible concen-tration of ground level ozone that is permitted in an area with organic lifeforms by theUnited States Navy. [17]

While ground level ozone is more harmful to the general population, due to its higherlikelihood of intake, tropospheric ozone is also extremely detrimental to health. The


average tropospheric ozone concentration in Bangalore is 0.331 ppm, as indicated bythe dark blue line on the graph. This translates to an AQI between 301 and 500, whichis considered ’hazardous’. It is to be noted that the AQI and standards are set only forground level ozone, not for tropospheric ozone. This obviously has less of an effect thandescribed on the population due to it having a much greater altitude, but the very highAQI expresses the severity of pollution in Bangalore.

In the comparison, the averages that have been calculated are only representative ofnight-time concentrations in Bangalore, which may lead to discrepancies between themeasured value and actual values. This is because the concentration of ground level andtropospheric ozone is lower at night due to reduced industrial activity. It is safe to saythat the eight hour and one hour averages in Bangalore are considerably higher than theobtained averages. It can be approximated that the daytime ozone concentration is up to 4times higher than the night-time value, which could mean that the absolute concentrationis higher than the set standards at all times. This has serious implications for Bangalore,which are elaborated upon in the Discussion section. [18]

4 Discussion

As mentioned in the previous section, this level of tropospheric ozone is above the Amer-ican, International, and Indian safety standards for tropospheric ozone. Additionally, it ispossible that the collected values are actually lower than the real values present in Ban-galore, due to the data being collected at night. This potentially has severe implicationsfor the populace of Bangalore. One effect is an increased health risk due to the extremelyhigh concentration of ozone. As outlined in section 1.1.2, exposure to ozone can lead toinhibited lung development, onset asthma, and premature mortality, at just a concentra-tion of 70 ppb. With an average ground level concentration of 0.101 ppm, or 101 ppb, itcan be assumed that these effects may be much more drastic. Additionally, the ecologicalimpact would also be magnified, with large decreases in crop yield, and could also lead tothe disarray of intricate and delicate environmental systems.

As seen in Figure 13 [19], as the ozone level rises to 0.1 ppm, the amount of dailycases of respiratory disease increases linearly to 114 per day. This is evidence of thetheorized effects discussed previously. It can be inferred that the trend remains linearfrom the data shown in the graph, so it is highly likely that the number of cases will onlyincrease as the ozone level increases. While these data values are from Ontario, Canada,it can be assumed that the effects of ozone on the human respiratory system are the sameworldwide. Considering that the average ozone level in Bangalore at night is 0.101 ppm,as found by this experiment, it is likely that the number of cases of respiratory disease inthe city will follow a similar trend.

It should be noted that the WHO decreased its acceptable standard of concentrationfrom 0.06 ppm to 0.05 ppm (8 hour mean). Its research showed that the number of deathswhen the ozone level was 0.05 ppm was up to 2% higher than the number of deathsat 0.035 ppm. Additionally, they concede that there is a possibility of long-term healtheffects due to exposure to ozone. The WHO also links the creation of ozone in the at-


FIGURE 13: Relationship between respiratory admissions and ozone level. Graph fromUnited Staes Environmental Protection Agency, adapted from Burnett et al., 1994

mosphere to gas emissions, as the reactants involved in this creation come from saidemissions. Also, the level of tropospheric ozone can be increased by leakages from thestratosphere, increasing the value past the measured value of 0.04 ppm. [5]

Figure 14 [19] shows that as the level of ozone increases, so does the decrease in lungfunction. FEV1 represents the drop in the volume exhaled by people tested. As seenon the graph, this effect is more intense in younger people, and could have long-lastingeffects. For example, people aged around 20 years old would experience a reduction inlung function by up to 1 liter at 0.4 ppm, with the average normal lung function being3.25 liters for women and 4.5 liters for men. This represents a reduction of approximately30% and 22% respectively, which satisfies the criteria for lung inhibition involved withmoderate COPD.

This study was conducted successfully, albeit with many limitations. For example,there exists a lack of studies on this topic in Bangalore, where the study took place. Thismade it very difficult to judge the accuracy of the collected data, and limited the optionsfor comparison of data. Additionally, as seniors in high school, the authors had limitedfunding options, and had to rely on other methods for resources, such as networking andconnecting to institutions, namely SSERD and IIA. Another limitation was the scarcity ofreliable sensors to be found in India. In fact, the sensors could not be found in India, andhad to be imported from the United States, which led to a large loss of time, shifting theproposed date of launch from early March to mid-April.


FIGURE 14: Effect on FEV of ozone. Graph from United Staes Environmental ProtectionAgency, adapted from Devlin et al., 1997.

5 Conclusions

In this project, a payload was launched to the troposphere with an ozone sensor, a tempera-ture sensor, and other components to measure the concentration of ozone. It was launchedusing two hydrogen-filled weather balloons with a width of 2.4384 meters. The sensorswere industrial standard sensors: an MQ131 ozone sensor and an MS5803-05BA temper-ature sensor. The sensors were tested at an industrial testing site, in order to evaluate boththeir durability and their accuracy.

To conclude, the concentration of ground level and tropospheric ozone found in Ban-galore is much higher than the safety standards set by various institutes. The night-timeaverages that have been obtained (0.101 ppm for ground level ozone, and 0.331 ppmfor tropospheric ozone) are considerably higher; hence, the day-time averages are almostcertainly higher. Tropospheric ozone, and more importantly ground level ozone, can bedetrimental to health, specifically in regards to actions such as breathing and other such


respiratory functions in the case of humans. Furthermore, it can also be disruptive to theecosystem in general. With a ground level ozone concentration of over 100 ppb, it is fea-sible to state that the general population would experience a reduction in FEV, as shownby studies regarding the effects of ozone on various age groups. The effect on all agegroups is prominent, with younger people being affected the most. Moreover, the numberof cases of respiratory ailments would be expected to increase as a result.

In order to produce more accurate results, a payload with more specialized equipmentand an attitude control system to orient the payload could be used to target specific seg-ments of the city and obtain a more detailed analysis. Finally, this experiment could berepeated across other major metropolitan cities to establish a comparison between thesemetropolitan areas.

6 Availability of data and materials

The data sets generated during and analyzed during the current study are available in the"BALLOON" repository, https://github.com/Nexus987/Balloon

7 List of abbreviations

• ppm - Parts per million

• ppb - Parts per billion

• mbar - Millibar

• mAh - Milliampere hour

• COPD - Chronic obstructive pulmonary disease

• FEV - Forced expiratory volume

8 Competing interests

The launch costs and the materials required to make the outer structure of our payloadbox were provided by the Indian Institute of Astrophysics. However, the institution didnot play any part in the data analysis or the writing of the paper. Hence, there were nofinancial conflicts of interest during the duration of research.

9 Funding

The project was financed by the team, SSERD and IIA. The former split the costs ofthe power bank, sensors, Bluetooth module, SD card, and board, while IIA providedthe Styrofoam, tape, and cotton tape needed for the payload box. SSERD was crucialin ensuring this project remained affordable. A large portion of the costs of testing theequipment and the launch vehicle costs were excluded thanks to SSERD’s support.


10 Authors’ contributions

AS conceived the idea about exploring the ozone profile above Bangalore, due to thereasons mentioned in the paper. AS further coordinated with all the parties involved,which included maintaining and meeting deadlines and managing all members of theteam. AS and GN worked on the initial stages of the project, such as discussing itsfeasibility and working out a timeline. AS searched and sourced the hardware needed forthe payload.

The payload was constructed with every author and co-author contributing, includingAS, RT, GN and RM. While AS and GN focused specifically on the mechanical aspectof the payload box, including making the compartments and constructing the air tunnel,RT and RM focused specifically on the software aspect, which included the electricalinterface, the coding, and the connections of all the equipment. AS, RT and RM wereessential during the testing phase of the sensors as well, while GN spent a considerableamount of time aiding during that time. The payload was finally fitted with all of theequipment, with all of the authors working on it.

AS, RT and RM were essential in the data analysis of the results. This involved theextrapolation and all the statistical analyses to draw conclusions from the data available.Furthermore, GN was essential during the writing of the manuscript. The majority ofthe manuscript was written by AS and GN, which was then proofread by RM and RT.RM further played a crucial role in coding and graphing all of the data obtained, andimplementing the ideas for analysis in code, with AS aiding in generating ideas for themathematical analysis. RT aided with the general analysis of the data and how accurateconclusions could be derived from the data, while having helped in all other areas of theproject as well.

Acknowledgments

We would like to thank SSERD, who gave us guidance throughout this entire process,and helped us pinpoint our idea and refine our focus. We extend a special thank you toNikitha, KR Abhishek , and Sujay Sreedhar, for their extensive help and invaluable inputs.

We would additionally like to thank IIA for their assistance with the construction andlaunch of our payload. We would like to thank Binu Balakrishnan for his assistance withthe construction of our payload, and Ms. Margarita Safanova for her accommodationof our utilization of IIA’s resources. Furthermore, we would like to thank Dr. JayanthMurthy for his invaluable support for the project, and allowing the usage of the launchvehicle for the payload.

We would like to thank SKC Labs, for allowing us to utilize their facilities to exten-sively test our payload, and for their support of this experiment. We also thank them foraccommodating the many hours we spent testing.

We would also like to thank Techgreen Solutions for their support, and for allowingus to use their facilities for testing.

We also would like to specifically thank Prafulla Sujatha Nagesh, for her extensive


contributions to the construction of the payload, as well as her assistance in the lab and asan environmental adviser.

We thank our school, Oakridge International School, Bangalore, for allowing us todo this project. We thank our career counselor, Ms. Hemalatha Yuvaraj, who offered usthis opportunity, and without whom this never would have happened. We also thank Mr.Sai Krishna Pammi, our coordinator, who accommodated the time we needed to spendworking at school, both during and after school hours. We would also like to thank ourprincipal, Ms. Hema Chennupaty, and our director, Mr. Amit Jain, for supporting us andattending the launch.

We thank our families for helping us finance this project, and for their undying supportin this project.

We also thank our friends for their support throughout this endeavor. We give a specialthank you to Gaurang Bharti and Vikram Mishra for their assistance with the code andlaunch, and for their support and coming to the launch.

References

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investigating the vertical ozone proﬁle, with a speciﬁc focus ......investigating the vertical...

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