A Text book for Xl Students

Sharon Sebastian Physical Science Reg.No: 18221383010

PREFACE Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural places. It should not be confused with green chemistry, which seeks to reduce potential pollution at its source. It can be defined as the study of the sources, reactions, transport, effects, and fates of chemical species in the air, soil, and water environments; and the effect of human activity and biological activity on these. Environmental chemistry is an interdisciplinary science that includes atmospheric, aquatic and soil chemistry, as well as heavily relying on analytical chemistry and being related to environmental and other areas of science. Environmental chemistry involves first understanding how the uncontaminated environment works, which chemicals in what concentrations are present naturally, and with what effects. Without this it would be impossible to accurately study the effects humans have on the environment through the release of chemicals. Environmental chemists draw on a range of concepts from chemistry and various environmental sciences to assist in their study of what is happening to a chemical species in the environment. Important general concepts from chemistry include understanding chemical reactions and equations, solutions, units, sampling and analytical techniques. This book gives a clear cut ides about the meaning of environmental chemistry, identify causes of ozone layer depletion and its effect. different types of pollutions. The students can get more information about environmental chemistry and important aspects of environmental chemistry. Also be a guide and support. Sharon Sebastian Physical Science Reg.No:18221383010

CONTENTS 1. Environmental Chemistry 2. Classification of the environment 3. Environmental pollution and it’s types 4. Tropospheric pollution 5. The greenhouse effect 6. Stratospheric pollution

CHAPTER 1 ENVIRONMENTAL CHEMISTRY Environmental chemistry is used by the Environment Agency in England Natural Resources Wales the United States Environmental Protection Agency,the Association of Public Analysts,and other environmental agencies and research bodies around the world to detect and identify the nature and source of pollutants. These can include:





Heavy metal contamination of land by industry. These can then be transported into water bodies and be taken up by living organisms. PAHs (Polycyclic Aromatic Hydrocarbon) in large bodies of water contaminated by oil spills or leaks. Many of the PAHs are carcinogens and are extremely toxic. They are regulated by concentration (ppb) using environmental chemistry and chromatography laboratory testing.




Nutrients leaching from agricultural land into water courses, which can lead to algal blooms and eutrophication.




Urban runoff of pollutants washing off impervious surfaces (roads, parking lots, and rooftops) during rain storms. Typical pollutants include gasoline,motor oil and other hydrocarbon compounds, metals, nutrients and sediment (soil).




Organometallic compounds.

When physical and biological components of the environment get contaminated up to such an extent that they start affecting the natural environmental processes and composition adversely, then this condition is called environmental pollution. The substances which cause pollution are called pollutants. Pollutants cannot be degraded by natural processes and remain in the environment for a long time and unbalance the composition of the environment which causes adverse effects on its natural processes.

In the end, when these natural environmental processes get adversely affected, then they impose adverse effects on human beings as well. The irony is these pollutants originate from various human activities such as overuse of plastic bags, over emission of carbon dioxide through factories and power plants, etc. Environmental pollution is the unfavorable alteration of our surroundings, wholly or largely as a byproduct of man's actions. through direct or indirect effects of the changes in the energy pattern, radiation levels, and chemical and physical constitution and abundance of organisms. Environmental pollution is a global problem and a common to both developed as well as developing countries, which attracts the attention of human beings for its severe long-term consequences.

The decline in environmental quality as a consequence of pollution is evidenced by loss of vegetation. biological diversity, excessive amounts of harmful chemicals in the ambient atmosphere and in food grains, and growing risks of environmental accidents and threats to life support systems. Pollution is viewed from different angles by different people but is commonly agreed to be the outcome of urbanindustrial and technological revolution and rapacious and speedy exploitation of natural resources, increased rate of exchange of matter and energy. and ever-increasing industrial wastes, urban effluents, and consumer goods. Holdgate (1979) defined environmental pollution as the introduction by man, into the environment, substances or energy liable to cause interference with legitimate uses of environment. Singh (1991) has defined pollution in a very simple manner, i.e., "Disequilibrium condition from equilibrium condition in any system." This definition may be applied to all types of pollution ranging from physical to economic, political, social, and religious.

Over the past couple of decades, various sources of pollution were identified that altered the composition of water, air, and soil of the environment. The substances that cause pollution are known as pollutants. A pollutant can be any chemical (toxic metal, radionuclide's, organo phosphorus compounds, gases) or geochemical substance (dust, sediment), biological organism or product, or physical substance (heat, radiation, sound wave) that is released intentionally or inadvertently by man into the environment with actual or potential adverse, harmful, unpleasant, or inconvenient effects. Such undesirable effects may be direct (affecting man) or indirect, being mediated via resource organisms or climate change. Depending on the nature of pollutants and also subsequent pollution of environmental components, the pollution may be categorized as follows: Among these types of pollution, air pollution is the main type threatening the environment, humans, plants, animals, and all living organisms.

Air pollution refers to the release of harmful contaminants (chemicals, toxic gases, particulates, biological molecules, etc.) into the earth's atmosphere. These

The effects of air pollution vary based on the kind of pollutant. But generally, the impact of air pollution ranges from:


Increased risk of respiratory illness and cardiovascular problems




Increased risk of skin diseases

2. Water Pollution




May increase the risk of cancer

3.Soil/Land Pollution




Global warming




Acid rain




Ozone depletion




Hazards to wildlife

1. Air Pollution

4. Noise Pollution 5. Radioactive Pollution 6.Thermal Pollution contaminants are quite detrimental and in some cases, pose serious health issues. Some causes that contribute to air pollution are:


Burning fossil fuels




Mining operations




Exhaust gases from industries and factories

Among the other types of pollution, air pollution is theorized to have a planetwide implication. Scientists have even speculated an apocalypse- like scenario where air pollution if left unchecked, can bring about an extreme form of global warming called the runaway greenhouse effect. Though this is purely speculative, it is a phenomenon that has already occurred on Venus.

Water pollution is said to occur when toxic pollutants and particulate matter are introduced into water bodies such as lakes, rivers and seas. These contaminants are generally introduced by human activities like improper sewage treatment and oil spills .However, even natural processes such as eutrophication can cause water pollution. Other significant causes of water pollution include:  Dumping solid wastes in water bodies  Disposing untreated industrial sewage into

water bodies  Human and animal wastes 

Agricultural runoff containing pesticides and fertilizers

The effects of water pollution are very pronounced in our environment. Furthermore, toxic chemicals can bioaccumulate in living beings, and these chemicals can travel their way up the food chain, ultimately reaching humans.

Among the other types of pollution, water pollution has a more disastrous consequences on humans. For instance, in 1932, a grave case of water pollution incapacitated the inhabitants of an entire city in Japan with neurological diseases and mental illness for many decades. However, the immediate cause was not apparent but was eventually attributed to acute mercury poisoning. Methyl mercury was dumped into the surrounding bay and had ultimately bioaccumulated inside the fish. The local population then consumed these fish, and this resulted in the manifestation of ill-effects and neurological diseases.

Soil pollution, also called soil contamination, refers to the degradation of land due to the presence of chemicals or other man-made substances in the soil. The xenobiotic substances alter the natural composition of soil and affect it negatively. These can drastically impact life directly or indirectly. For instance, any toxic chemicals present in the soil will g absorbed by the plants. Since plants are producers in an environment, it gets passed up through the food chain.. Compared to the other types of pollution, the effects of soil pollution are a little more obscured, but their implications are very noticeable. Some of the common causes of soil pollution are: 

Improper industrial waste disposal

 Oil Spills  Acid rain which is caused by air pollution  Mining activities  Intensive farming and agrochemicals (like

fertilisers and pesticides)  Industrial Accidents

The effects of soil pollution are numerous. Specific wastes, such as radioactive waste become particularly hazardous when they are not wellcontained. A well-documented example is a nuclear accident in Chernobyl, which has left an area of 2,600 km2 uninhabitable for several thousand years. Other effects of soil pollution include: 

Loss of soil nutrients, which renders the soil unfit for agriculture.



Impacts the natural flora and fauna residing in the soil.



Degrades vegetation due to the increase of salinity of the soil.



Toxic dust (such as silica dust) can cause respiratory problems or even lung cancer.

Noise pollution refers to the excessive amount of noise in the surrounding that disrupts the natural balance. Usually, it is man-made, though certain natural calamities like volcanoes can contribute to noise pollution. In general, any sound which is over 85 decibels is considered to be detrimental. Also, the duration an individual is exposed plays an impact on their health. For perspective, a normal conversation is around 60 decibels, and a jet taking off is around 150 decibels. Consequently, noise pollution is more obvious than the other types of pollution. Noise pollution has several contributors, which include: o

Industry-oriented noises such as heavy machines, mills, factories, etc.

o

Transportation noises from vehicles, aeroplanes, etc.

o

Construction noises

o

Noise from social events (loudspeakers, firecrackers, etc.)

o

Household noises (such as mixers, TV, washing machines, etc.)

Noise pollution has now become very common due to dense urbanization and industrialization. Noise pollution can bring about adverse effects such as:


Hearing loss




Tinnitus




Sleeping disorders




Hypertension (high BP)




Communication problems

CHAPTER 2 CLASSIFICATION OF THE ENVIRONMENT The topic essentially involves the classification of the Under Of Environment various layers the atmosphere. The atmosphere is a mixture of a number of gases that surround the Earth and acts as its cover. Here are the layers of the atmosphere: Troposphere This is the first or the lowest layer of the atmosphere, ranging from the Earth's surface to the Stratosphere. It contains water vapors and has the greatest influence on air pollution. Stratosphere It is right above the Troposphere and below the Mesosphere. The ozone layer is also present in this region.

Mesosphere This is the third layer which is above the Stratosphere and below the Thermosphere. The Mesosphere is the coldest region of the entire atmosphere with a temperature ranging from -2 to 92 degrees Celsius. Thermosphere The upper region of the atmosphere that is right above the Mesosphere is known as the Thermosphere. It is the hottest region of the atmosphere with a temperature of around 1200 degrees Celsius. Exosphere This is the top-most layer of the atmosphere which contains various ionic or atomic compounds of oxygen, hydrogen, and helium.

Hydrosphere This is the aqueous cover or envelope around the Earth, which includes oceans, lakes, and other water bodies. Lithosphere This is the rock-solid portion, which includes the mountains and other rocky bodies of the Earth. Biosphere This is the foremost biological envelope of the Earth that supports living beings like animals, birds, human beings, etc.

CHAPTER 3 ENVIRONMENTAL POLLUTION AND ITS TYPES The contamination of the environment or the presence of unwanted/toxic substances in natural resources or the environment is known as environmental pollution. The toxicity in the resources arises mostly due to human activities through natural disasters. All of these can highly contaminate the atmosphere, air, and soil. As there are various types of pollutants and their causes, we will now study them in detail. Mentioned below is an advanced categorization of types of pollution: Natural Pollution Natural pollution is caused by natural resources or nature- based activities, for example, volcanic eruptions, methane gas release from the paddy fields, forest fires, etc.

Man-Made Pollution Man-made pollution results from the excessive interference of humans in nature, or activities like burning fuel, industrial effluents, excessive use of pesticides and chemicals, deforestation, etc. Pollutants

The substance which is either produced by natural activities or man-made activities that can potentially affect the natural composition of the environment is known as a pollutant. Pollutants also trigger pollution at a higher level. Pollutants can be bifurcated into two categories depending upon their nature: Biodegradable Pollutants The pollutants that can be degraded by the microbial or biological actions of nature are known as biodegradable pollutants. For example, natural wastes, or domestic sewage. Non-Biodegradable Pollutants The pollutants that cannot be degraded or acted upon by the biological on microbial activities are known as nonbiodegradable pollutants. They undergo biological magnification which can be of two types such as wastes including glass, phenols, plastic, etc. and poison including pesticides, radioactive substances, heavy metals, etc.

CHAPTER 4 TROPOSPHERIC POLLUTION Tropospheric environmental pollution occurs due to the presence of toxic or undesirable gaseous or solid substances in the air. The major pollutants causing this pollution are:


Gaseous Pollutants such as oxides of nitrogen, sulfur, carbon, hydrocarbons, ozone, hydrogen sulfide, oxidants, etc.




Particulate Pollutants including fumes, dust, smog, mist, smoke, etc.

H₂₂O (liq) + CO2 (gas) -> H₂₂Coз (aq) There can be several sources that result in acid rain, but it mostly occurs because of the burning of fossil fuels. This contains highly toxic nitrogenous or sulfur matter like coal, petrol, or diesel that produces sulphur dioxide or nitrogen oxides.

Acid Rain When the highly acidic compounds in the atmosphere react with rainwater, they increase the acidic level of water and result in acid rain. The pH level of rainwater is 5.6, which is acidic due to the presence of the H+ ions formed by the reaction of acidic compounds present in the atmosphere.

The SO2 and NO₂ chemicals, after the oxidation reaction with water, resulting in acid rain. This polluted water contains a number of particulate matters that catalyze the oxidation reactions.

What Causes Acid Rain? Acid rain is the rain that has been acidified, with a pH less than 5.6. Excessive amounts of sulfur. and nitrogen released by cars and industrial processes get mixed with rain and result in precipitation that is highly acidic. Sulfur and Nitrogen particles may be released in the atmosphere due to anthropogenic causes or by natural causes. Anthropogenic causes include industrial emissions, burning of fossil fuels such as diesel and coal, incineration of garbage, production of paper. Natural causes could be release of sulfur during volcanic eruptions or nitrogen ions released in the atmosphere during a lightning strike. The chemical reaction occurs in the presence of lightning to form the nitric oxide. This further reacts with oxygen to form nitrogen dioxide. Furthermore, ozone, some other organic acids like formic and acetic acids also contribute to 5-20% acidity in total acid rain.

Effects of Acid Rain In this section, we talk about the impact of acid rain on the environment as well as infrastructure. Acid rains damage standing crops and forests. It has adverse impact on freshwater life, other aquatic life forms, insects etc. Acid rain can cause the ocean's pH to fall. This phenomenon is known as 'ocean acidification'. Though acid rain does not have huge impacts on oceans, they significantly affect shallower coastal waters. Excess nitrogen inputs from the atmosphere in the oceans promote increased growth of marine plants and phytoplankton which may result in more frequent harmful algal blooms and eutrophication. Limestone skeleton in Corals is sensitive to decrease in pH levels, as calcium carbonate the core component of the limestone skeleton dissolves in low pH/acidic solutions. Some microbes in the soil cannot tolerate changes to low pH and get killed. The enzymes of these microbes are denatured by the acid.

It corrodes structures as well as buildings. Example: Acid rains have turned the Taj Mahal's marble yellow. Acid rain also causes the corrosion of water pipes which further results in leaching of heavy metals such as iron, lead and copper into drinking water. Acid rain does not harm humans immediately. The sulfur dioxide creates various health problems. It can cause lung inflammation including asthma, bronchitis and emphysema. Controlling the anthropogenic causes of acid rain by keeping a check on industrial and vehicular emissions is one of the most significant steps in reducing acid rains. Policy interventions to reduce such emissions is the need of the hour. Additionally, renewable sources of energy through fewer emissions can help reduce acid rain.

Effects of Acid Rain Acid rain is very harmful to agriculture, plants, and animals. It washes away all nutrients which are required for the growth and survival of plants. Acid rain affects agriculture by the way it alters the composition of the soil. Acid rain effect on plants It causes respiratory issues in animals and humans. When acid rain falls down and flows into the rivers and ponds it affects the aquatic ecosystem. It alters the chemical composition of the water, to a form which is actually harmful to the aquatic ecosystem to survive and causes water pollution. Acid rain also causes the corrosion of water pipes, which further results in leaching of heavy metals such as iron, lead and copper into drinking water. It damages the buildings and monuments made up of stones and metals

CHAPTER 5

THE GREENHOUSE EFFECT More than 70% of the solar energy entering the ecosystem of the Earth is absorbed by the Earth's surface, which results in an increase in temperature. The remaining heat and solar energy radiate back to the Earth's atmosphere. Some traces of the heat remain trapped by gases like methane, carbon dioxide, ozone, water vapor, or chlorofluorocarbon compounds. This further increases the temperature of the atmosphere and causes global warming. Greenhouse gases are one of the factors behind the increase in the Earth's temperature and melting polar ice caps. Ultimately it results in the consequential submerging of the coastal landmass. The greenhouse. gases are carbon dioxide, ozone, methane, chlorofluorocarbons, water vapor, etc.

Altogether they increase the Earth's temperature and the possibilities of the spread of infectious diseases, Which gases cause the greenhouse effect? The contribution that a greenhouse gas makes to the greenhouse effect depends on how much heat it absorbs, how much it re-radiates and how much of it is in the atmosphere. In descending order, the gases that contribute most to the Earth's greenhouse effect are:  water vapor (H2O) 

carbon dioxide (CO2)

 nitrous oxide(N20) 

methane (CH4)

 ozone (03)

In terms of the amount of heat these gases can absorb and re-radiate (known as their global warming potential or GWP), CH4 is 23 times more effective and N20 is 296 times more effective than CO2. However, there is much more CO2 in the Earth's atmosphere than there is CH4 or N2O. Not all the greenhouse gas that we emit to the atmosphere remains there Indefinitely. For example, the amount of CO2 in the atmosphere and the amount of CO2 dissolved in surface waters of the oceans stay in equilibrium, because the air and water mix well at the sea surface. When we add more CO2 to the atmosphere, a proportion of it dissolves into the oceans Anthropogenic greenhouse The "greenhouse effect" of the atmosphere is named by analogy to greenhouses which become warmer in sunlight. However, a greenhouse is not primarily warmed by the "greenhouse effect".

"Greenhouse effect" is actually a misnomer since heating in the usual greenhouse is due to the reduction of convection, while the "greenhouse effect" works by preventing absorbed heat from leaving the structure through radiative transfer. A greenhouse is built of any material that passes sunlight: usually glass or plastic. The sun warms the ground and contents inside just like the outside, and these then warm the air. Outside, the warm air near the surface rises and mixes with cooler air aloft, keeping the temperature lower than inside, where the air continues to heat up because it is confined within the greenhouse. This can be demonstrated by opening a small window near the roof of greenhouse: the a temperature will drop considerably. It demonstrated experimentally (R. W. Wood, 1909) that a (not heated) "greenhouse" with a cover of rock salt (which is was 20 transparent to infrared) heats up an enclosure similarly to one with a glass cover.

Thus greenhouses work primarily by preventing convective cooling. Heated greenhouses are yet another matter: as they have an internal source of heating. it is desirable to minimize the amount of heat leaking out by radiative cooling. This can be done through the use of adequate glazing. It is possible in theory to build a greenhouse that lowers its thermal emissivity during dark hours; such a greenhouse would trap heat by two different physical mechanisms, combining multiple greenhouse effects, one of which more closely resembles the atmospheric mechanism, rendering the misnomer debate moot.

CHAPTER 6

STRATOSPHERIC POLLUTION At high altitudes to the atmosphere consists of a layer of ozone (03) which acts as an umbrella or shield for harmful UV radiations. It protects us from harmful effect such as skin cancer. UV radiation can convert molecular oxygen into ozone as shown in the following reaction. Ozone gas thermodynamically unstable and readily decomposes to molecular oxygen. Depletion of Ozone Layer (Ozone hole) In recent years, a gradual depletion of this protective ozone layer has been reported. Nitric oxide and CFC are found to be most responsible for depletion of ozone layer. Generally substances that cause depletion of ozone or make it thinner are called Ozone Depletion Substances abbreviated as ODS.

The loss of ozone molecules in the upper atmosphere is termed as depletion of stratospheric ozone.

Oxides of Nitrogen Nitrogen oxides introduced directly into the stratosphere by the supersonic jet aircraft engines in the form of exhaust gases. These oxides are also released released by combustion of fossil fuels and nitrogen fertilizers. Inert nitrous oxidein the stratosphere is photo chemically converted into more reactive nitric oxide. Oxides of nitrogen catalyze the decomposition of ozone and are themselves regenerated. Ozone gets depleted as shown above.

They slowly pass from troposphere to stratosphere. They stay for very longer period of 50- 100 years. In the presence of uv radiation, CFC's break up into chlorine free radical. Chlorine radical is regenerated in the course of reaction. Due to this continuous attack of CI thinning of ozone layer takes place which leads to formation of ozone hole it is estimated that for every reactive chlorine atom generated in the stratosphere 1,00,000 molecules of ozone are depleted.

Thus NO is regenerated in the chain reaction Environmental Impact of Ozone Depletion Chloro Fluoro Carbons (CFC) Freons The chloro fluoro derivatives of methane and ethane are referred by trade name Freons. These Chlora Fluoro Carbon compounds stable, non- noncorrosive and inflammable, are toxic, non- easily liquefiable and are used in refrigerators, air- conditioners and in the production of plastic foams. CFC's are the exhaust of supersonic air craft's and jumbo jets flying in the upper atmosphere.

The formation and destruction of ozone is a regular natural process, which never disturbs the equilibrium level of ozone in the stratosphere. Any change in the equilibrium level of the ozone in the atmosphere will adversely affect life in the biosphere in the following ways.

Depletion of ozone layer will allow more UV rays to reach the earth surface and layer would cause skin cancer and also decrease the immunity level in human beings. UV radiation affects plant proteins which leads to harmful mutation of cells. UV radiation affects the growth of phytoplankton, as a result ocean food chain is disturbed and even damages the fish productivity.