Smog And Acid Rain

Smog is the visible gaseous and particular matter concentrating near the earth's surface particularly in the cities due to SO2, CO2, factory and traffic emission and meteorological conditions. Acid rain may be defined as any precipitation such as rain, fog, mist or snow which is more acidic than the normal i.e. having a lower pH than that of normal rain water. The term acid rain was first referred by Robert Angus in 1872.Acid rain is due to presences of various pollutants like oxides of nitrogen, carbon, sulphur, and halogens radicals or molecules in the atmosphere have become the serious problem in most industrialized countries.

Summary

Smog is the visible gaseous and particular matter concentrating near the earth's surface particularly in the cities due to SO2, CO2, factory and traffic emission and meteorological conditions. Acid rain may be defined as any precipitation such as rain, fog, mist or snow which is more acidic than the normal i.e. having a lower pH than that of normal rain water. The term acid rain was first referred by Robert Angus in 1872.Acid rain is due to presences of various pollutants like oxides of nitrogen, carbon, sulphur, and halogens radicals or molecules in the atmosphere have become the serious problem in most industrialized countries.

Things to Remember

 

  • Smog is the visible gaseous and particular matter concentrating near the earth's surface particularly in the cities due to SO2, CO2, factory and traffic emission and meteorological conditions.
  • Photochemical smog is characterized by the brown misty haze which irritates the eyes and lungs,lead to the cracking of rubber and extensive damage to plant life.
  • Two types of Photochemical smog:- 
    i. Sulphurous Smog
    ii. Los Angeles smog

    • The presences of ozone, PANs and aldehydes in smog leads to eyes irritations and affects respiratory tracts and throts.
    • The presences of PANs in smog causes extensive agricultural and forestry damage, such as damage to leaves and stomatal tissues.

 

MCQs

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Subjective Questions

Q1:

Explain the Mechanism of menstruation or menstrual cycle ?


Type: Long Difficulty: Easy

Show/Hide Answer
Answer: <p><strong>Mechanism of menstruation or menstrual cycle</strong></p>
<p>The cyclic process of menstruation is known as menstrual cycle, which is the preparation for a pregnancy whenever pregnancy does not occur, the endometrium degenerate and the cycle recommeces . It occurs normally every 28-30 days but sometines everu 21-42 days.</p>
<p>&nbsp;</p>
<p>There are 3 main organs involved in this cycle. Each organ has its own cycle for completion of a menstrual cycle.</p>
<ol>
<li>Pituitary gland</li>
<li>The ovary and</li>
<li>The uterus</li>
</ol>
<p>&nbsp;</p>
<ol>
<li><strong> The pituitary gland</strong></li>
</ol>
<p>The hypothalamus secrets luteinizing hormones releasing hormone. This stimulate the anterior pituitary gland to secrete :</p>
<ol>
<li>Follicle stimulating hormones ( FSH ), which promote the maturation of ovarian follicles and the secretion of estrogen, leading to ovulation. It increase until ovulation and then it is gradually declined.</li>
<li>Luteinizing hormone ( LH), which stimulates the development of corpus luteum and secretion of progesterone. The hormone made thick, vascular and spongy to the endometrium.</li>
</ol>
<p>&nbsp;</p>
<p>The secretion of FHS and LH stimulates by changes in the blood concentration of hotmones. Hormones secreted in the cycle are regulated by negative feedback mechanism.</p>
<p>&nbsp;</p>
<ol start="2">
<li><strong> The ovarian cycle</strong></li>
</ol>
<p>From hormonal stimulation , one or more ovum to be discharged at a time under influence of FHS. The ovary produce estrogen and progestwwhich made the endometrium thick, vascular and spongy, which is shed during menstruation. Each ovary ovulates at two monthly intervals. The remaining membranes granulose cells proliferate under the influence of LH.</p>
<p>&nbsp;</p>
<ol start="3">
<li><strong> The uterine cycle or menstrual cycle</strong></li>
</ol>
<p>The interval between first menstruation to next menstruation is known the menstrual cycle. The menstrual cycle involves a series of events which occur at regular interval over a period of about 28 days involving three distinct phases ;</p>
<ol>
<li>The proliferative phase - 10 days</li>
<li>The secretory phase - 14 days</li>
</ol>
<p>iii. The menstrual phase - 4 days</p>
<p>&nbsp;</p>
<ol>
<li><strong> The proliferative phase</strong></li>
</ol>
<p>This phase begins at the end of menstruation. During this phase, the anterior lobe of the pituitary gland secretes the FSH . This hormone develop and mature primordial follicle into graafian follicle. During this period usually only one ovum grows develop and matures but sometimes two or more may do so.</p>
<p>&nbsp;</p>
<p>During this period ovary secrete a hormone estrogen. This hormones passes directly into the blood stream and has its effect upon the endometrium, stimulating the columnar cells to reproduce the endometrium more rapidly forming a thicker lining and increasing the number of glands and blood capillaries cause more vascular and spongy. This phase lasts up to 10 days from 4th days of previous menstruation. By the end of this phase the endometrium becomes 2-3 mm thick.</p>
<p>&nbsp;</p>
<p>When ovum is mature, the high level of luteinizing hormone cause the follicle rupture and the ovum is come out into the peritoneal cavity. The release of the ovum from the follicle is termed as ovulation. This phase ends when ovulation occurs and secretary phase begins.</p>
<p>&nbsp;</p>
<ol>
<li><strong> The secretary phase</strong></li>
</ol>
<p>The phase begins after ovulation and last for about 2 weeks or 14 days. Immediately after ovulation, the pituitary glands starts to secret the second gonadotrophin, the luteinizing hormone.</p>
<p>&nbsp;</p>
<p>This hormone stimulates the remaining cells of the ovarian follicles to form corpus luteum or yellow body. The corpus luteum under the influence of the luteinizing hormone start to secrete the second ovarian hormone progesterone.</p>
<p>&nbsp;</p>
<p>Progesterone is directly absorbed into the blood stream and has an effect on the endometrium augmenting the action of estrogen. It causes further thickening of the lining, the endometrial glands becomes larger and more tortuous, store large amount of glycogen increasing blood capillaries and begins secretory activity. The gland increase their secretion which is released into the uterine cavity.</p>
<p>&nbsp;</p>
<p>The endometrium is now thick, soft , moist , vascular and rich in blood capillaries and is prepared to receive fertilized ovum . The endometrium has a thickness of 4-6 mm.</p>
<p>&nbsp;</p>
<p>If the ovum is ferilized, there is no break down of the endometrium and no menstrual flow. Thus endometrium is now called decidua. The fertilized ovum embeds itself within the endometrium and produce a hormone called human chorionic gonadotrophin hormone which keeps the corpus luteum intact and thus allows it to continue secreting progesterone.</p>
<p>&nbsp;</p>
<p>If the ovum is not fertilized, then menstrual bleeding begins.</p>
<p>&nbsp;</p>
<p><strong>iii. The menstrual phase</strong></p>
<p>If the ovum is not fertilized, the high level of progesterone in the blood inhibit the activity of the pituitary gland and the production of LH is considerably reduced. The withdrawal of this hormone cause shrink and degeneration of the corpus luteum and thus progesterone production is decreased. This cause degeneration and disintegration of inner lining of uterus cause menstrual bleeding. It contains blood, inner lining cell, unfertilized ovum. This lasts for about 4-6 days. The normal amount of blood flow at each cycle is approximately 60-90 ml.</p>
<p>&nbsp;</p>
<p>When the progesterone level in the blood falls to a certain level the pituitary gland again starts to secrete the follicle stimulating hormone . Another ovarian follicle is stimulated and the cycle starts again</p>

Videos

Ovulation & the menstrual cycle
The Menstrual Cycle
Smog And Acid Rain

Smog And Acid Rain

Smog

Smog is the visible gaseous and particular matter concentrating near the earth's surface particularly in the cities due to SO2, CO2, factory and traffic emission and meteorological conditions. When different gases like SO2, NO2, N2O, NO2, unburnt hydrocarbons etc. are released into the atmosphere, they form photochemical smog ( smoke + fog) which become harmful pollutant.

The important constituents of smog are oxides of nitrogen and sulphur, carbon monoxides, hydrogen peroxide, peroxy acetyl nitrate (PAN) , peroxy benzoyl nitrate (PBN) ,peracetic acid hydroperoxide etc. These chemical are released into the air by smoke coming out of industries, from automobile exhaust, fossil burning etc. In addition, hydrocarbons discharged from automobiles react with nascent oxygen or ozone to produces aldehydes, ketones or organic peroxies which are also present in smog.

Photochemical smog is characterized by the brown misty haze which irritates the eyes and lungs,lead to the cracking of rubber and extensive damage to plant life. In plants, prolonged exposures damage chloroplasts, disturb electron transport system and adversely affects a number of enzymes which play a vital role in photosynthesis.

There are various types of photochemical smog. For example :-

  1. Sulphurous Smog

It is the mixture of fog , smoke and sulphur dioxide (SO2) gas. This type of smog was marked in London in 1952 where the smog prevailed for fice days killing few thousands. The pollution was caused due to sulphur dioxide and smoke during a temperature inversion. The effects were more severe in morning hours and became deadly after sunrise because of photochemical oxidation. The smog caused bronchitis, pneumonia, respiratory, distress, and eye diseases.

S + O2→ SO2

SO2+ O→ SO3

SO2+ H2O → H2SO3

H2SO3+ O→H2SO4

H2SO4+ NH3→ (NH4)2SO4

  1. Los Angeles Smog

Such type of smog was recorded for the first time at Los Angeles in 1944 and there after it is known as Los Angeles smog. The smog contains different times of a day. In the morning, when nitric oxide (NO) is discharged from automobile exhausts build up and react with oxygen to form nitrogen dioxide which is a yellowish brown gas with pungent and chocking odour. Since NO2gas produces a characteristic brown haze, the cities where this type of smog predominates, are called brown air cities. As the sunrises, the UV-rays cause a rapid conversion of NO2to NO and the nascent oxygen atom. The nascent oxygen atoms react with oxygen molecules of air to give ozone (O3). The other highly reactive chemical forms are hydrogen peroxide (H2O2) , hydroxy radicals (OH) etc.
NO2→ NO + O
NO + O2→ NO2+ O
NO2→ PAN + O2
O2+ O→ O3

The molecules like PAN, ozone , NOxetc. are the major components of smog. Nitrogen combines with oxygen to produce a mixture of oxides . In the morning, the concentration of NO is maximum and after the sunshine , NO2becomes higher.

N2+ 2O2→ 2NO2

2NO + O2→ 2NO2

NO + O→ NO

2NO2+ O→ N2O5

O3+ 2NO2→ N2O5+ O2

Effects of smog

The formation of smog is highly destructive and influences both the physiological and metabolic activities of living organisms. Some important effects of smog are given below:

  1. The presences of ozone, PANs and aldehydes in smog leads to eyes irritations and affects respiratory tracts and throts.
  2. The presences of PANs in smog causes extensive agricultural and forestry damage, such as damage to leaves and stomatal tissues.
  3. The presences of NO2in smog causes nose and eye irritation and chronic diseases in lungs and heart.
  4. PANs cause dizziness and headache in man.
  5. Ozone decolourises the paintings.
  6. Smog damages metals, paper, rubber and fabrics.
  7. The particulate matters in smog induce lung cancer.
  8. Smoke cause early maturity of plants and reduces the rate of photosynthesis.

Control of smog

  1. The production of nitrogen oxide (NOx) and hydrocarbon should be controlled which checks the production of ozone and PANs.
  2. The process like incineration, absorption, and condensation should be employed to reduce the different harmful constituents of smog such as oxides of sulphur and nitrogen, hydrogen carbon, carbon-monoxides, dust etc.

Acid Rain

Acid rain is one of the major environmental pollutions of these days. Acid rain may be defined as any precipitation such as rain, fog, mist or snow which is more acidic than the normal i.e. having a lower pH than that of normal rain water. The normal rain water is also slightly acidic having pH approximately 5.6. When the acid content becomes high and pH falls down to 5.4 or even up to 2.0,we call it acid rain.

The term acid rain was first referred by Robert Angus in 1872 and it has became a serious problem in most of the industrialized countries. Acid rain is due to presences of various pollutants like oxides of nitrogen, carbon, sulphur, and halogens radicals or molecules in the atmosphere.This pollutants are discharged into the atmosphere by several natural processes like volcanic eruptions, forest fires, lightning, burning of fossils fuels, decomposition of organic matters etc and human activities like automobile exhausts burning of fuels, thermal power plants, petroleum refinery etc.

The conversion of the pollutant into their corresponding acids are shown in the equations given below:

N2+ O2→ 2NO (nitric oxide)

NO + O3→ NO2+ O2

2NO2+ O3→ N2O3+ 2O2

2NO + O→ N2O5(nitrogen pentoxide)

N2O5+ H2O→ 2HNO3(Nitric Acid)

N2O3+ H2O → 2HNO2(Nitrous Acid)

S + O2 → SO2(sulphur dioxide)

2SO2 + O2→ 2SO3( sulphur trioxide)

SO3+ H2O→ H2SO4(sulphuric acid)

SO2+ H2O→ H2SO3(sulphurous acid)

C + O2→ CO2

CaCO3→ Cao + CO2

CO2 +H2O→ H2CO3 (carbonic acid)

Cl2→ Cl• + Cl•

H2→ H• + H•

H• + Cl• → HCL (hydrochloric acid)

The concentrations of these acids, as well as the quality of water in which the acids are dissolved, determine the pH of rain water. Heavy rains are usually less acidic as there is relatively more water. On the other hand, fogs and mists are more acidic as the acid molecules are dissolved in relatively little water.

Effects of Acid rain

The damage caused by acid precipitation (acid rain) are of a very diverse nature and can be sammed up as follows :

  1. The corrosive action of the acid content in these rains damages buildings, monuments, statues, bridges, fences, wood, cement, concrete structure, railings etc.
    CaCO3 + H2SO4→ CaSO4 + CO2 + H2O
  2. Acid rain increases the soil acidity affecting land flora and fauna.
  3. Diseases caused by bacteria and pathogens can be spread by acid rain water.
  4. Acid rain may cause respiratory and skin diseases.
  5. It leaches various metals such as aluminium, zinc, copper, manganese, cadmium, lead etc. from the soil into aquatic bodies. When the concentration of these metals increases beyond the safe limit, it affects development and leads to the death of many aquatic organisms in general and fishes in particular.
  6. It affects the drinking water storage sources.
  7. It causes acidification of aquatic bodies, which leads to the killing of aquatic plants and animals.The increase in acidity also affects the metabolism, growths and development of aquatic organisms.
  8. Plants and animals addicts by the acid rains are easy attacked by pathogens.

Control Measures

Acid rain can only be controlled by managing the sources of the pollution. Some important control measures are given below:

  1. The fuels, devoid of sulphur or having low sulphur amounts should be used to minimise the amount of sulphur dioxide gas in the atmosphere.
  2. The vehicular exhaust should be minimised by using control values in the outlet of the exhaust pipeline of the automobiles.
  3. The aquatic bodies and farmlands should be periodically limed to neutralise the acidity due to acid rain.
  4. The leakage of chlorine or it's discharge should be stopped.
  5. The scrubbers should be used to reduce the emission of SO2 during coal burning.
  6. SO2gas released is sprayed with water containing lime, which precipitates SO2as calcium sulphite ( CaSO3).
    Ca(OH)2 + SO2→ CaSO3+ H2O
  7. General public awareness should be created regarding the ill effects of environmental pollution and consequences of acid rain.

References

Adhikari, N.R.Plus two practical chemistry.Nepal: Ed-mark Academic Enterprises Pvt. Ltd, 2004.

Jain, S.K.Conceptual Chemistry,.Vol. I and II. S. Chand & Company Ltd., n.d.

Khatri, S.S.Elementary Principles of General Chemistry.TU Kathmandu: Curriculum Development Centre , 1997.

Wagley, Dr. P.Compressive Chemistry.Nepal: WorldWide Publication Pvt. Ltd, 2014.

Lesson

Environmental Pollution

Subject

Chemistry

Grade

Grade 11

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