Answer

Environmental chemistry is the scientific study of the chemical and biochemical phenomena that occur in natural places. It involves understanding how chemical substances interact with the environment, including the air,water,soil, and living organisms. This field of chemistry focuses on the source,reaction,transport,effect, and fate of chemical species in the environment. It often involves the study of pollution and the solution to environmental problems, such as the development of more environmentally friendly chemical process and products.

Answer

Tropospheric pollution refers to the presence of harmful substance in the Earth’s lowest atmospheric layer, the troposphere. Key pollutants include nitrogen oxides, sulfur dioxide, carbon monoxide, volatile organic compounds, and particulate matter. These pollutants primarily originate from humans activites like industrial process, vehicle emissions, and burning fossil fuels. Tropospheric pollution leads to the formation of ground-level ozone and smog, which can harm human health, damage vegetation, and contribute to climate change. Natural sources, such as wildfires and volcanic eruptions, also contribute. Managing tropospheric pollution involves regulating emission, promoting cleaner technologies, and enhancing air quality monitoring.

Answer

Carbon dioxide $(CO_2)$ and carbon monoxide $(CO)$ gases are emitted during the combustion of various fuels. Carbon monoxide is poisonous, whereas carbon-dioxide is non-toxic in nature.

Carbon monoxide is poisonous because it is capable of forming a complex with haemoglobin (carboxyhaemoglobin), which is more stable than the oxygen-haemoglobin complex. The concentration range of $3-4 $ % of carboxyhaemoglobin decreases the oxygen-carrying capacity of blood. This results in headaches, weak eyesight, nervousness, and cardiovascular disorders. A more increased concentration may even lead to death.

Carbon dioxide is not poisonous. It proves harmful only at very high concentrations.

Answer

The major greenhouse gases are:

1. Carbon dioxide $(CO_2)$
2. Methane $(CH_4)$
3. Water $(H_2 O)$
4. Nitrous oxide $(N_2O)$
5. Ozone $(O_3)$
6. Chlorofluorocarbons $(CFCs)$

Answer

Acid rain is a byproduct of various human activities that leads to the emission of oxides of sulphur and nitrogen in the atmosphere. These oxides undergo oxidation and then react with water vapour to form acids.

$ \begin{aligned} & 2 SO _{2}(g)+O _{2}(g)+2 H_2 O {(l)} \longrightarrow 2 H_2 SO _{4}(a q) \\ & 4 NO _{2}(g)+O _{2}(g)+2 H_2 O {(l)} \longrightarrow 4 HNO _{3}(a q) \end{aligned} $

Acid rain causes damage to buildings and structures made of stone and metal. In India, limestone is a major stone used in the construction of various monuments and statues, including the Taj Mahal.

Acid rain reacts with limestone as:

$CaCO_3+H_2 SO_4 \longrightarrow CaSO_4+H_2 O+CO_2$

This results in the loss of lustre and colour of monuments, leading to their disfiguration.

Answer

Smog is a type of air pollution. It is a blend of smoke and fog. Smog is classified into classical smog and photochemical smog.

Classical smog occurs in a cool, humid climate. Its components include smoke, fog and sulphur dioxide. It is reducing in nature.

Photochemical smog occurs in a dry, sunny climate. Its components are PAN, acrolein, ozone, formaldehyde, nitric oxide. It is oxidizing in nature.

Answer

Formation of Nitric oxide and Nascent Oxygen:

The first reaction involves nitrogen dioxide $\left(\mathrm{NO}_2\right)$ reacting under sunlight.

The equation for this reaction is:

$ \mathrm{NO}_2(g)+\text { sunlight } \rightarrow \mathrm{NO}(g)+\mathrm{O}(\text { nascent }) $

In this reaction, nitrogen dioxide is converted into nitric oxide $(\mathrm{NO})$ and nascent oxygen ( O ).

Formation of Ozone:

The nascent oxygen produced in the first step reacts with molecular oxygen $\left(\mathrm{O}_2\right)$ to form ozone $\left(\mathrm{O}_3\right)$.

The equation for this reaction is:

$ \mathrm{O}(\text { nascent })+\mathrm{O}_2(\mathrm{~g}) \rightarrow \mathrm{O}_3(\mathrm{~g}) $

This reaction is reversible, meaning ozone can also decompose back into nascent oxygen and molecular oxygen.

Reaction of Ozone with Nitric Oxide:

Ozone then reacts with nitric oxide to regenerate nitrogen dioxide and produce more oxygen.

The equation for this reaction is:

$ \mathrm{O}_3(\mathrm{~g})+\mathrm{NO}(\mathrm{~g}) \rightarrow \mathrm{NO}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) $

Formation of Formaldehyde:

Ozone can also react with hydrocarbons, such as methane $\left(\mathrm{CH}_4\right)$, to produce formaldehyde $(\mathrm{HCHO})$ and water $\left(\mathrm{H}_2 \mathrm{O}\right)$.

The equation for this reaction is:

$ \mathrm{O}_3(\mathrm{~g})+\mathrm{CH}_4(\mathrm{~g}) \rightarrow \mathrm{HCHO}(\mathrm{~g})+\mathrm{H}_2 \mathrm{O}(\mathrm{~g}) $

Answer

Harmful effects of photochemical smog:

(i) It corrode metals, stones, rubber and painted surface.

(ii) It causes serious health problems to senior citizens, children and people with heart and lung problems which lead to emphysema, bronchitis, asthma.

(iii) It causes pneumonia, inflammation of pulmonary tissues, fatigue, heart palpitations, premature aging of lungs and death.

Control measures:

(i) The release of $\mathrm{NO}_2$ and hydrocarbons in the atmosphere can be prevented by using catalytic converters.

(ii) Switching over to other types of fuels, desulfurization of fuel gases from coal fired power plants, expansion of public rail transport.

(iii) Since plants can metabolize $\mathrm{NO}_2$, Pinus, Juniparur, Quercus, Pyrus and Vitis should be planted.

Answer

UV radiations act on dioxygen to form ozone.

$\mathrm{O}_{2} (\mathrm{g}) \xrightarrow{\mathrm{uv}} \mathrm{O}{(\mathrm{g})}+\mathrm{O}{(\mathrm{g})}$

There is dynamic equilibrium between the production and decomposition of ozone.

$\mathrm{O}{2}(\mathrm{g})+\mathrm{O}{(\mathrm{g})} \stackrel{\mathrm{uv}}{\longleftrightarrow} \mathrm{O}{3}(\mathrm{~g})$

The disturbance of this equilibrium results in ozone depletion. Chlorofluorocarbons mix with atmospheric gases and reach the stratosphere, where they are decomposed by UV rays to produce chlorine free radicals.

$\mathrm{CF}2 \mathrm{Cl}{2}(\mathrm{g}) \xrightarrow{\mathrm{uv}} \dot{\mathrm{C}} \mathrm{I}{(\mathrm{g})}+\dot{\mathrm{C}} \mathrm{F}_2 \mathrm{Cl}{(g)}$

These chlorine free radicals react with ozone to form oxygen and ClO• free radicals which react with atomic O to produce more chlorine free radicals.

$\dot{\mathrm{C}} \mathrm{I}{(g)}+\mathrm{O}{3}(\mathrm{~g}) \longrightarrow \mathrm{Cl} \dot{\mathrm{O}}{(g)}+\mathrm{O}{2} (g)$

This results in continuous breakdown of ozone present in the stratosphere damaging the ozone layer.

$\mathrm{Cl} \dot{\mathrm{O}}{(\mathrm{g})}+\mathrm{O}{(\mathrm{g})} \longrightarrow \dot{\mathrm{Cl}}{(\mathrm{g})}+\mathrm{O}_{2}(g)$

Answer

The “Ozone hole " refers to the significant depletion of the ozone layer in the Earth’s stratosphere, Particularly over Antarctica. This phenomenon is primarily caused by human-made chemicals called Chloroflorocarbons (CFCs) and other Ozone-depleting substances. These chemicals release Chlorine and bromine atoms in the stratosphere, which then break down ozone molecules.

Consequences of the Ozone Hole:

Increase UV radiation:

More harmful ultraviolet (UV) radiation reaches the Earth’s surface, leading to higher risks of skin cancer, cataracts, and other health issues.

Ecosystem damage:

Increased UV levels can affect marine ecosystem, particularly plankton,which form the base of oceanic food chains.

Agriculture impact:

Crops and other plants life can suffer from increased UV exposure, affecting growth and yield.

Answer

Industrial waste:

Industries produce large amount of waste materials such as toxic chemicals and pollutants such as lead, mercury, sulphur, asbestos, nitrates and many other harmful chemicals.

Improper waste management system and the disposal of waste into the fresh water causes water pollution.

Sewage and waste water:

The sewage water produced by each household carries harmful bacteria known as pathogens which causes deadly diseases.

Accidental Oil leakage:

Oil spills poses a great threat to the marine wildlife as large amount of oil does not dissolve with water.

Chemical fertilizers and pesticides:

Chemical fertilizers and pesticides used by farmers to protect crops from pests are useful for the plants growth.

But when it rains, these chemicals mixes up with rainwater and flows down into rivers and canals which pose serious damages for aquatic animals.

Radioactive waste:

The element used in production of nuclear energy is Uranium which is a highly toxic chemical.

The nuclear waste produced by the radioactive material can have serious environmental hazards if not disposed off properly.

Leakage from the landfills:

Landfills are huge piles of garbage seen across the city that produces awful smell.

During rainy season, the landfills may leak that can pollute the underground water with large variety of contaminants.

Answer

Water pollution arises as a result of various human activities. This includes discharges from wastewater treatment plants, run-off from agricultural fields, storm-water drainage, etc. Pollutants from these sources enter the water bodies, thereby contaminating the water and rendering it impure.

Industries and chemical factories discharge toxic, heavy metals such as $Fe, Mn, Al$, etc., along with organic wastes into water. Domestic sewage and animal excreta are also responsible for pathogenic contamination of water. These pollutants make water unfit for drinking.

Therefore, all industrial and chemical discharges should be made free from toxic metals before allowing them to enter a water body. The concentration of these pollutants should be checked regularly. Compost should be preferred over chemical fertilizers in gardens and agricultural fields to avoid harmful chemicals from entering ground water.

Answer

Biochemical oxygen demand is the amount of oxygen required by bacteria to decompose organic matter in a certain volume of sample of water. Clean water would have a BOD value of less than $5 ppm$, whereas highly polluted water has a BOD value of 17 ppm or more.

Answer

Yes, we can easily observe the soil pollution in our neighborhood which is mainly carried out by the industrial wastes and agricultural pollutants like pesticides and fertilisers. It can be controlled by the following methods:

• Excessive use of insecticides and pesticides should be avoided.

• Insecticides like DDT are insoluble in water. Due to which, they remain in soil for a long time, contaminating the root crops.

• The use of polythenes should be avoided.

• Non-biodegradable waste should be recycled rather than burying in the soil or burning.

• Household waste, biological waste and chemical waste is often incinerated. Incineration greatly reduces waste volume.

Answer

A mixture of two or more substances used for killing pests are called pesticides. pests include insects, plant pathogens, weeds, mollusks, etc, that destroy the plant crop and spread diseases. Aldrin and dieldrin are the names of some common pesticides.

Herbicides are pesticides specially meant for killing weeds. Examples include sodium chlroride $\left(\mathrm{NaClO}_3\right)$, sodium arsenite $\left(\mathrm{Na}_3 \mathrm{AsO}_3\right)$ etc.

Answer

Green chemistry is a production process that aims at using the existing knowledge and principles of chemistry for developing and implementing chemical products and processes to reduce the use and generation of substances hazardous to the environment.

The release of different harmful chemicals (particulates, gases, organic and inorganic wastes) causes environmental pollution. In green chemistry, the reactants to be used in chemical reactions are chosen in such a way that the yield of the end products is up to $100 %$. This prevents or limits chemical pollutants from being introduced into the environment. Through the efforts of green chemists, $H_2 O_2$ has replaced tetrachlorethane and chlorine gas in drying and bleaching of paper.

Answer

Earth’s most abundant greenhouse gases are $CO_2, CH_4, O_3, CFCs$, and water vapour. These gases are present near the Earth’s surface. They absorb solar energy that is radiated back from the surface of the Earth. The absorption of radiation results in the heating up of the atmosphere. Hence, greenhouse gases are essential for maintaining the temperature of the Earth for the sustenance of life.

In the absence of greenhouse gases, the average temperature of the Earth will decrease drastically, making it uninhabitable. As a result, life on Earth would be impossible.

Answer

The amount of dissolved oxygen present in water is limited. The abundance of phytoplanktons causes depletion of this dissolved oxygen. This is because, phytoplanktons are degraded by bacteria present in water. For their decomposition, they require a large amount of oxygen. Hence, they consume the oxygen dissolved in water. As a result, the BOD level of water drops below 6 ppm, inhibiting the growth of fish and causing excessive fish-kill.

Answer

Depending upon the nature of the waste, domestic waste can be segregated into two categories i.e., biodegradable and non-biodegradable.

Biodegradable waste such as leaves, rotten food, etc. should be deposited in land fills, where they get decomposed aerobically and anaerobically into manure.

Non-biodegradable waste (which cannot be degraded) such as plastic, glass, metal scraps etc. should be sent for recycling.

Answer

It is essential to take proper care of the compost producing pit in order to protect ourselves from bad odour and flies. It should be kept covered to minimize bad odour and prevent flies from entering it.

The recyclable waste should not be dumped in the compost producing pit. It should be sent to the industries through vendors for recycling.