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SMOG Binesh Siddiqui Lecturer – Chemistry

INRTRODUCTION Smog is an air pollution which occurs when harmful substances including particulates and molecules are introduced into Earth's atmosphere. It may cause diseases, allergies or death of humans; it may also cause harm to other living organisms such as animals and food crops, and may damage the natural or built environment. Human activity and natural processes can both generate air pollution. What is Smog The term "smog" was first used in London during the early 1900's to describe the combination of smoke (pollutants) and fog (water droplet) that often blanketed the city. The pollutants present in the environment are trapped in the water droplets forming grey fumes which is called SMOG. List of the Common Industrial Gases Following is the list of pollutants which are normally present in the environment.

Ammonia (NH3)

Carbon dioxide (CO2)

Carbon monoxide (CO)

Hydrogen chloride (HCl)

Topic: Troposphere-I

Commecs Perspective

Patron

Cdr (Retd) Abdul Razaq PN

Convener

Dr. Uzma Naveed

Incharge

Rohana Tariq

January 2018

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Oxides of nitrogen

Nitrogen trifluoride (NF3)

Sulphur dioxide (SO2)

Sulphur hexafluoride (SF6) Gases/Pollutants Present in Smog Following is the list of the pollutants which are present in the smog

NOx

Volatile organic compounds

Ozone.

PAN (peroxyAcetal nitrate)

Carbon monoxide (CO)

Carbon dioxide (CO2) Sources of Pollutants Man Made Smog Is Derived From

Coal emission

Vehicular emission

Industrial emission

Forest and agricultural fire

Photochemical reactions of the above emissions

Chemistry Involved in the Formation of the Pollutants When fossil fuel is burnt it emits hydrocarbons and nitric oxides which further oxidized to nitrogen dioxide. Nitrogen dioxide absorbs sun light energy and breaks up into nitric oxide and free oxygen, this formed free oxygen reacts with oxygen and converts into ozone. Formation of proxy acetal nitrate takes place when ozone and nitrogen dioxide formed in the above reaction reacts with the unburnt fuel (primary precursor) in the polluted air. Required Conditions for Smog Formation Following conditions favour the smog formation

Still Day (No Wind)

Sun Light

Temperature Inversion

Temperature Inversion It is a Phenomenon in which warm air stays near the ground instead of rising above and the wind stays calm, smog may remain trapped over a city for days.

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Hazards Caused by the Smog

Smog is a serious danger to elderly, toddlers and ill.

Both ozone and PAN act as eye irritants

Ozone and nitric oxide irritate nose and throat.

High concentrations of these cause headache chest pains and dryness of the throat, cause respiratory disease such as asthma and bronchitis.

Harms the agriculture along with the animals.

Photochemical smog leads to cracking of rubber and extensive damage to plant life.

Data Showing Smog Affect Air pollution in urban areas is getting worse. According to WHO between 2008 and 2013, global urban air pollution levels rose by 8%. Some 80% of all urban areas have air pollution levels above what's considered healthy by the World Health Organization, a new report said that the rate is even more dismal

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for cities with more than 100,000 people in low- and middle-income countries. The report found that 98% of those areas had unhealthy air.

The most harmful pollutant to human health is called PM 2.5, particle matter smaller than 2.5 microns in diameter that's found in soot, smoke, and dust. PM 2.5 is especially dangerous because it can get lodged in the lungs and cause long-term health problems like asthma and chronic lung disease. PM 2.5 starts to become a major health problem when there is more than 35.5 micrograms (µg) of PM 2.5 per cubic meter of air, according to the Environmental Protection Agency. But the World Health Organizations recommends keeping yearly average PM 2.5 levels three times lower than that.

For a safe and healthy life important measures such as Installation of air purifiers and home pollution detectors are being practiced in developed countries. But In developing countries like Pakistan, where it is difficult to utilize the advanced methods and technology for protection we should take basic precautions like, avoid going outside and wearing mask while going outside in smog.

Troposphere and its impact on life of Earth Sana Noman Lecturer – Biology

INTRODUCTION: The atmosphere looks like a blanket of gas when we look at it from space or the ground. Atmosphere consist of different parts and different layers. There are layers of different molecules, temperatures, and pressures. Overall, the atmosphere is made up of a few main molecules. The air above us is made of 78% nitrogen (N2), 21% oxygen (O2), 0.9% argon (Ar) and 0.04% carbon dioxide (CO2). That's it. The rest of it is made of things called trace elements. Those trace elements include water vapor, ozone, and other particles and molecules floating around. LAYERS OF ATMOSPHERE: Earth's atmosphere has a series of layers, each with its own specific traits. Moving upward from ground level, these layers are named the troposphere, stratosphere, mesosphere, thermosphere and exosphere. The exosphere gradually fades away into the realm of interplanetary space. TROPOSHERE: The troposphere is the lowest layer of our atmosphere. Starting at ground level, it extends upward to about 10 km (6.2 miles or about 33,000 feet) above sea level. We humans live in the troposphere, and

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nearly all weather occurs in this lowest layer. Most clouds appear here, mainly because 99% of the water vapor in the atmosphere is found in the troposphere. Air pressure drops, and temperatures get colder, as we climb higher in the troposphere. TROPOSPHERIC OZONE, THE POLLUTER: Ozone occurs naturally at ground-level in low concentrations. The two major sources of natural ground-

level ozone are hydrocarbons, which are released by plants and soil, and small amounts of stratospheric ozone, which occasionally migrate down to the earth's surface. Neither of these sources contributes enough ozone to be considered a threat to the health of humans or the environment. But the ozone that is a byproduct of certain human activities does become a problem at ground level and this is what we think of as 'bad' ozone. With

increasing populations, more automobiles, and more industry, there's more ozone in the lower atmosphere. Since 1900 the amount of ozone near the earth's surface has more than doubled. Unlike most other air pollutants, ozone is not directly emitted from any one source. Tropospheric ozone is formed by the interaction of sunlight, particularly ultraviolet light, with hydrocarbons and nitrogen oxides, which are emitted by automobiles, gasoline vapors, fossil fuel power plants, refineries, and certain other industries. Almost all the countries in Asia agree to protect the ozone layer by taking measures to control the production and consumption of substances that deplete it. Yet as the interactive map indicates, the impact of Ozone pollution is widespread in Asia. From China’s smog-hit cities, to India’s changing rainfall patterns, to losses of crop yields in Japan and Pakistan, to premature deaths in many other countries - Ozone poses a threat to human life and live-hood. High ozone levels are commonly responsible for an increasing number of asthma attacks and other respiratory health diseases, especially when children and the elderly are concerned. GROUND LEVEL OZONE: Ground-level or "bad" ozone is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline vapors, and chemical solvents are some of the major sources of NOx and VOC. Breathing ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma. Ground-level ozone also can reduce lung function and inflame the linings of the lungs. Repeated exposure may permanently scar lung tissue. Ground-level ozone also damages vegetation and ecosystems.

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How can ground-level ozone affect our health

Ozone can irritate respiratory system, causing one to start coughing, feel an irritation in throat and/ or experience an uncomfortable sensation in chest.

Ozone can reduce lung function and make it more difficult to breathe as deeply and vigorously as one normally would. When this happens, it may be noticed that breathing starts to feel uncomfortable. While exercising or working outdoors, breathing gets rapid and shallow than normal.

Ozone can aggravate asthma. When ozone levels are high, more people with asthma have attacks that require a doctor’s attention or the use of additional medication.

One reason this happens is that ozone makes people more sensitive to allergens, which are the most common triggers for asthma attacks. Also, asthmatics are more severely affected by the reduced lung function and irritation that ozone causes in the respiratory system.

Ozone can inflame and damage cells that line lungs. Within a few days, the damaged cells are replaced and the old cells are shed—much in the way skin peels after a sunburn. Ozone may aggravate chronic lung diseases such as emphysema and bronchitis and reduce the immune system’s ability to fight off bacterial infections in the respiratory system.

Ozone may cause permanent lung damage. Repeated short-term ozone damage to children’s developing lungs may lead to reduced lung function in adulthood. In adults, ozone exposure may accelerate the natural decline in lung function that occurs as part of the normal aging process. ENVIROMENTAL EFFECT: Ground-level ozone can have detrimental effects on plants and ecosystems. These effects include:

interfering with the ability of sensitive plants to produce and store food, making them more susceptible to certain diseases, insects, other pollutants, competition and harsh weather;

damaging the leaves of trees and other plants, negatively impacting the appearance of urban vegetation, as well as vegetation in national parks and recreation areas; and

reducing forest growth and crop yields, potentially impacting species diversity in ecosystems. REDUCING OZONE POLLUTION: There are several ways to decrease ozone pollution:

Limit using your automobile during afternoon and early evening hours in the late spring, summer and early fall.

Do not use gasoline-powered lawn equipment during these times.

Do not fuel your car during these times.

Do not light fires or outdoor grills during these times.

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Keep the engine of your car or boat tuned.

Make sure that your tires are properly inflated.

Use environmentally safe paints, cleaning and office products (some of these chemicals are sources of VOC).

Conserve energy. One of the most important steps to take is to tell friends, family and co-workers what you are doing and why. Education and small modification of activities will do wonders for keeping the air cleaner in your corner of the world.

Chemistry of Trophosphere Sobeya Rizwan Lecturer– Chemistry

The word troposphere means ‘turning sphere’, which symbolizes the fact that, in this region, convective processes dominate over radiative processes. The term troposphere was first used in 1902 by Léon

Philippe Teisserenc de Bort, a French meteorologist who was a pioneer in the use of meteorological balloons. The troposphere is the lowest layer of Earth's atmosphere. The troposphere starts at Earth's surface and goes up to a height of 7 to 20 km (4 to 12 miles, or 23,000 to 65,000 feet) above sea level. Most of the mass (about 75-80%) of the atmosphere is in the troposphere. Almost all weather occurs within this layer. The layer above the troposphere is called the stratosphere. The boundary between the top of the troposphere and the stratosphere is called the tropopause. Nearly all atmospheric water vapour or moisture is found in the troposphere. The troposphere is heated from below. Sunlight warms the ground

or ocean, which in turn radiates the heat into the air right above it. The top of the troposphere is quite cold. The temperature there is around -55° C (-64° F).Near the equator, the tropopause is about 20 km (12 miles or 65,000 feet) above sea level. The thickness of the troposphere varies from about 7 to 8 km (5 mi) at the poles to about 16 to 18 km (10 to 11 mi) at the Equator. In addition, it varies in height according to season, being thinner in winter when the air is densest. Atmospheric Chemistry of Earth's Troposphere: When we think of chemistry, we think about mixing colored liquids in test tubes and maybe making an explosion or at least a nice puff of smoke, a lot of chemistry happens in Earth's atmosphere. There are many different kinds of chemicals in the air. Those chemicals often combine with each other in chemical reactions, making new and different chemicals. This is called "atmospheric chemistry". Most of the gas in our atmosphere is nitrogen. About 4/5ths of the air is nitrogen. The other 1/5th is oxygen, There are also very small amounts of a bunch of other

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chemicals. Greenhouse gases trap the heat from sunlight in our atmosphere. Earth would be very cold if we didn't have any greenhouse gases. Carbon dioxide and methane are two very important greenhouse gases. Some of the chemicals in the air come from pollution. When we burn coal in a factory or gasoline in our cars, we make air pollution. Coal and oil have sulfur in them. When they burn, they make chemicals called sulfur oxides. These can turn into sulfuric acid when they mix with water droplets in the air. These droplets of acid can fall to the ground as acid rain. Cars and trucks also give off chemicals called nitrogen oxides. Nitrogen oxides combine with other chemicals to make smog. They also help make nitric acid, which is another acid in acid rain. Nature also does things to change the chemistry of the troposphere. Volcanoes, lightning, and wildfires all add chemicals to the air or change the ones that are already there. Energy from sunlight can make chemical reactions happen, changing one gas into another. Some chemicals move in cycles between the atmosphere, living creatures, and the oceans. The Carbon Cycle and the Nitrogen Cycles are two important cycles that change the chemistry of the atmosphere. Ozone in the Troposphere: Ozone is found in two different layers of the atmosphere. You may have heard of the ozone hole problem

- that is a lack of ozone in the stratosphere (the 2nd layer of the Earth's atomsphere). But ozone is also found in the troposphere, the first layer of the Earth’s atmosphere. In the troposphere, ozone is NOT wanted! It can actually do a lot of damage. Ozone is released naturally in the troposphere by plants and soil. These are such small amounts that they are not harmful to the health of humans, animals or the environment. Ozone that increases because of certain human

activities does become a problem at ground level and this is what we think of as 'bad' ozone. With increasing populations, more automobiles, and more industry (power plants and refineries in particular), there's more ozone in the lower atmosphere. Since 1900, the amount of ozone near the Earth's surface has more than doubled. In urban areas in the Northern Hemisphere, high ozone levels usually occur during the warm, sunny, summer months (from May through September). Tropospheric ozone is formed by the interaction of sunlight, particularly ultraviolet light, with hydrocarbons and nitrogen oxides, which are emitted by automobiles, gasoline vapors, fossil fuel power plants, refineries, and certain other industries. Negative Impacts of Tropospheric Ozone: While stratospheric ozone shields us from ultraviolet radiation, in the troposphere this irritating, reactive molecule damages forests and crops; destroys nylon, rubber, and other materials; and injures or destroys living tissue. Smog can damage lung tissues. Rubber, fibers, and certain paints may be damaged by exposure to ozone. Some elastic materials can become brittle and crack, while paints and fabric dyes may fade more quickly. Ozone affects plants in

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several ways. High concentrations of ozone cause plants to close their stomata. These are the cells on the underside of the plant that allow carbon dioxide and water to diffuse into the plant tissue. This slows down photosynthesis and plant growth. Ozone may also enter the plants through the stomata and directly damage internal cells. So why can't we take all of this "bad" ozone and blast it up into the Stratosphere where ozone is wanted? Unfortunately, the vehicle necessary to transport such enormous amounts of ozone into the stratosphere does not exist, and, if it did, it would require so much fuel that the resulting pollution might undo any positive effect. We can turn to simpler solutions though, decreasing the production of those chemicals that create ozone in the troposphere. That means choosing to take public transportation instead of all driving separate cars, walking to school or work, and maybe even buying a new hybrid car! Health Effects: Health effects depend on ozone precursors, which are a group of pollutants, primarily generated during the combustion of fossil fuels. Irritation of the respiratory system, causing coughing, throat irritation, or an uncomfortable sensation in the chest. A statistical study of 95 large urban communities in the United States found significant association between ozone levels and premature death. The study estimated that a one-third reduction in urban ozone concentrations would save roughly 4000 lives per year (Bell et al., 2004). Tropospheric Ozone causes approximately 22,000 premature deaths per year in 25 countries in the European Union. (WHO, 2008) Climate Change: Melting of sea ice, releases molecular chlorine, which reacts with UV radiation to produce chlorine radicals. Because chlorine radicals are highly reactive, they can expedite the degradation of methane and tropospheric ozone and the oxidation of mercury to more toxic forms. Ozone production rises during heat waves, because plants absorb less ozone. It is estimated that curtailed ozone absorption by plants is responsible for the loss of 460 lives in the UK in the hot summer of 2006. A similar investigation to assess the joint effects of ozone and heat during the European heat waves in 2003, concluded that these appear to be additive.

Thermal Structure of the Troposphere Wajahat Afzal Lecturer– Physics

The preliminary Excel model of the thermal structure of the troposphere is based on a global energy budget. The model calculates the flow of energy between the troposphere and the surface of the Earth based on incident sunlight and atmospheric and surface optical and thermal properties specified by the analyst. The model also estimates the thermal structure of the troposphere which is defined as the temperature as a function of altitude including the surface of the planet and ranging to 10 km. The textbook standard temperature profile is described by the normal lapse rate of 6.5K per km. The global average surface temperature is reported to be 288K and temperature decreases 6.5K/km typically in the

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troposphere before rising and falling and rising again in the thin upper atmosphere where extreme ultraviolet is absorbed by ozone and other gases. The model fills the niche between simple global energy budgets that treat the atmosphere as a single layer and advanced research models that are extremely complex. Most of the mass of the atmosphere is in the troposphere and the troposphere model has many simplifying assumptions especially concerning the upper atmosphere. The model is preliminary because there are many effects that can be incorporated if time allows and because many assumptions and approximations need to be investigated further. Specifically, the model ignores the relationship between composition and optical and thermal properties, distribution of water vapor with altitude, the upper atmosphere, wavelength-dependent effects other than the broad bands of short vs. long wavelength, latitude dependent effects, and variations due to clouds and due to surface features like oceans vs. land.

Figure 1 The spectrum of sunlight includes ultraviolet, visible, and near infrared wavelengths much of which is absorbed or

scattered by the atmosphere even without clouds present. The model was used to investigate the Earth’s atmosphere with and without the benefit of latent heat transport, the effect of variations in greenhouse gas long wavelength absorption, the effect of a faint young Sun (four billion years ago), the effect of a highly reflecting surface (Snowball Earth nearly one billion years ago), and the effects of higher solar flux and extreme greenhouses as found on Venus. Figure 1 shows the spectrum of sunlight incident on the Earth’s atmosphere when the Sun is directly overhead. On a cloudless day, the direct beam that reaches the Earth’s surface is reduced by scattering losses shown in blue and by absorption shown in black. The atmosphere of the planet is continuously intercepting a solar flux of 1372 watts per square meter if the slight ellipticity of the Earth’s orbit is ignored. Locally this flux varies from zero on the side of the rotating planet that is facing away from the Sun to 1372 w/m2 where the Sun is directly overhead, such as the Equator at local noon on an Equinox. The nearly spherical planet intercepts a disk of sunlight equal to πR2, where R is the average radius of planet, which bulges at the Equator due to the rapid rotational velocity. Although this solar power is non-uniformly distributed over a sphere of surface area 4πR2, the average global flux is 343 w/m2 at all times, 24 hours a day all year long. The local daily average at the Equator on an Equinox is 1372w/m2/2 or 686 w/m2. In the winter, the daily average at a pole is zero. The global average flux is therefore one fourth of the peak or 343 w/m2.

absorption by ozone, water, and CO2

absorption by ozone, water, and CO2

scattering by N2, O2 and aerosolsscattering by N2, O2 and aerosols

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Some of the flux incident on the top of the atmosphere is absorbed or scattered before reaching the surface of the planet. Absorption and scattering varies with path length through the atmosphere which varies with altitude, latitude, seasons, and time of day. Absorption and scattering by clouds and by clear skies varies with wavelength and with composition, especially moisture content. Absorption by the Earth’s surface varies from deep blue oceans to bare land to vegetation.

Figure 2 All of the solar energy absorbed by the Earth’s surface and atmosphere is radiated as long wavelength infrared

“blackbody” radiation

Figure 2 shows that the energy radiated in the long wavelength infrared has the same area as the energy absorbed by the Earth even though their spectral distributions are very different. All of the flux intercepted by the Earth is returned to space in order to maintain thermodynamic equilibrium. Since the Earth’s albedo is about 30%, the remaining 70% of the incident flux is absorbed by the atmosphere or surface which radiates it away as blackbody radiation into space. The atmosphere and surface of the Earth transfer energy by radiation, convection, conduction, and evaporation/condensation of moisture, but only radiation can transport energy into space. Figure 3 below shows the absorption spectrum of several major triatomic greenhouse gases that trap outgoing long wavelength radiation and help elevate the average surface temperature of the Earth to 288K well above the effective atmospheric temperature of 255K.

Figure 3 The Earth’s average surface temperature is 288K because of long wavelength absorption by greenhouse gases

In our model, the troposphere is divided into 20 layers represented by 20 rows in the Excel spreadsheet. The model could have been divided into 10 layers or 40 layers or any other number. Energy is transported

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by convection as well as electromagnetic radiation throughout the troposphere, so the concept of layers is a numerical modeling term, not a description of physical features. The model calculates the energy flow in each layer and estimates the temperature of the Earth’s surface and each layer of the troposphere by using a modified version of the Stefan Boltzmann blackbody radiation law that accounts for the partial transparency of the atmosphere. The outputs of the model include all of the fluxes in the energy budget and a temperature profile in the troposphere which can be compared to the standard lapse rate of 6.5K per km. The model inputs can be varied to analyze the effect of variations of in the properties of the atmosphere, the surface of the planet, and the output of the Sun which is known to change over billions of years. The model relates properties of the planet to energy flow but it does not derive the properties from fundamental characteristics like the density and composition of the atmosphere, oceans, and land. A more advanced model could include these relationships but would probably need to include wavelength dependent effects. A more advanced model could include local variations from the global averages and could include horizontal energy flow on the Earth’s surface.

Climate Change in Pakistan Waqar Hussain Lecturer– Physics

Due to its geographic location Pakistan is in the list of countries that are highly affected by climate change and global warming.

Pakistan lies at slightly north of tropic of cancer with Arabian Sea at its south. Pakistan is at the junction of three famous mountain ranges that include Karakoram, Himalayas and Hindukush these mountain are the third largest mass of ice after the polar region. Annual temperature Variation: Pakistan has large number of weather stations that keeps the record of continues weather variables such as

temperature the record is maintained analyzed that gives the idea about the day to day climate variation. Figure below shows the plot of annual temperature record from 1960 to 2010. A rising trend can be seen which is the due the global warming.

Mountain Ranges of the Karakorum Himalaya

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Consequences Global warming in Pakistan: Pakistan has more than 5000 Glacier that supply water to its citizens by melting process that is balanced by winter snow fall but this balance has been disturbed by the global temperature rise. The global warming has caused the increased rate of melting glacier ice the water that is received in large amount due to the melting glacier runs down to the region of Punjab and Sindh that are at lower elevation causing floods that destroys the regions of standing cops and cultivated land regions.

Glaciers are not the only thing that is affected by global warming the southern region of Pakistan especially the province of Sindh is in last few years frequency of heat waves have increased drastically. The famous heats wave that occurred in June 2015 that took more than 2000 lives in less than 10 days by heat stroke and dehydration is the part of this change. Sea level Rise is another consequence of climate change in Pakistan Figure below shows the data plotted that have been collected at Gwadar during the period of 5 years. The data is clearly showing the rising trend. If this trend continues consequences will be very severe causing floods in the coast areas of Pakistan such as Gwadar and Karachi.

February, 2018

Troposphere-II Submission Date

January 31, 2018

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