1.2 Water, Air And Land

WATER, AIR & LAND INTER RELATIONSHIPS & SUB COMPONENTS     

Water Air Land Inter relationship between Components Sub Components

This is an interesting topic. In this topic, you are supposed to understand air, water and land as components of environment (elaborate on these three components as essays, if required). An elementary knowledge of water, air and land mainly their basics, sources, status and role in earth should be acquired. We shall be studying technical details of these components in UNIT 2.

WATER In this topic, we need to have a basic knowledge of water in the perspective that it is an environment component. We will cover the following for the environment component “water” •

Facts about Water

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Special Properties of Water

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Forms of Water

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Water as an Environment Component

FACTS ABOUT WATER: Most of you should know already and some of you should be startled to know the following facts related to water. (1) 70% of the human body is water. (2) Life on earth probably originated in water. (3) More than half of the world's animal and plant species live in the water. (4) Almost 75% of the earth is covered in water. (5) The human body needs 2 litres of water a day in our climate; we can last only a few days without water. (6) Most of our food is water: tomatoes (95%), spinach (91%), milk (90%), apples (85%), potatoes (80%), beef (61%).

Water is such an environment component and is the most viable and cherished environment component on comparison with land and air. Normally, water is a liquid substance made of molecules containing one atom of oxygen and two atoms of hydrogen (H2O). Pure water has no colour, no taste, no smell, turns to a solid at 0°C and a vapour at 100°C. Its density is 1 gram per cubic centimetre (1 g/cm3), and it is an extremely good solvent. SPECIAL PROPERTIES OF WATER: There are a few unique properties of water that make it so unique and necessary for living things. They are pondered upon in this section. Water exists in three forms: Water can and only water can exist on our planet in three physical states (i.e. state of matter) under them ambient conditions that normally occur. Water can be a liquid (water), a gas vapor (clouds), or a solid (ice). Water has the best thermal properties: Off all fluids, solids and gases, water has remarkable thermal properties like high latent heat of vaporization, heat absorption capacity etc. Water has the highest heat capacity of any liquid or solid, and can absorb a tremendous amount of heat. For this reason, the oceans of the world tend to vary in temperature much less than land. The average range of temperatures in the ocean is from -2 degrees to 35 degrees C. On land, temperatures may vary anywhere from -70 degrees to 57 degrees C. Compare also the moon, which has no water. Temperatures here range from -155 degrees to 135 degrees C.Thus, water acts like a heat buffer for the globe. Its ability to absorb heat at one location and transport it to another locations is extremely important in moderating the climate of our globe. Water has a neutral pH: pH is a measure of the acidity or alkalinity of a substance. For our purposes, you just need to know that some liquids are acidic (having more hydrogen ions) and some are basic (having more hydroxyls, or OH ions). The pH scale ranges from 0 to 14. The lower the pH the greater is the acidity. Conversely, the higher the pH, the more alkaline is a substance. Pure water has a pH of 7, which is neutral. This is once again a unique property of water. Water’s Density Pressure/Temperature Relationship: The density of liquids and gases can change depending on the temperature. Increases in temperature

usually decrease the density of substances, i.e. the spaces between the molecules in the substance expand. Decreases in temperature typically cause the density to increase, that is, the molecules in the substance get closer together, i.e. they contract. Variations in density also occur as a function of pressure. As pressure on a substance increases, its density increases. Where decreases in pressure occur, substances expand and become less dense. As the temperature of water decreases, water becomes denser, as expected. However, at temperatures below 4 degrees C, a very unusual thing happens to water -- it begins to expand. In other words, the density of water reaches a maximum at 4 degrees C; below and above this temperature, the density of water decreases. This unusual property of water is what allows ice to float. Because water freezes below 4 degrees C, i.e. at 0 degrees C, ice is less dense than water. The reason for this apparent anomaly is that at 4 degrees C, water molecules are packed as tight as they will go. Any attempt to push them closer together, such as by lowering the temperature, only makes the water molecules push back harder, i.e. they repel each other. Water molecules at the freezing point form a crystal lattice structure, like ice and snow, that is significantly less dense that liquid water. Water is a polar molecule : Water's unique properties are largely a result of its simple composition and structure. As mentioned above, water is composed of two hydrogen atoms bound to one oxygen atom. As shown in the diagram, the two hydrogen atoms are smaller (the smallest atom there is, in fact) and they rest on both sides of the larger oxygen atom at an angle of 105°. When the hydrogen atoms combine with oxygen, they each give away their single electron and form what is known as a covalent bond. Because electrons are more attracted to the positively charged oxygen atom, the two hydrogens become slightly positively charged (they give away their negative charge) and the oxygen atom becomes negatively charged. This separation between negative and positive charges creates what is known as a polar molecule, meaning a molecule that has an electrical charge on its surface somewhere. Although the water molecule as a whole has no charge, the parts of it, the hydrogen wings and the oxygen body, do exhibit individual charges.

Water dissolves almost anything: More substances dissolve in water than in any other liquid. For this reason, water is often called the "Universal Solvent." The reason for water's excellent dissolving capability relates to its polarity; water offers positive and negative charges to which other atoms of molecules can attach. Note how water molecules can surround the positive sodium ion or the negative chloride ion, the common components of table salt. Water surrounds positive atoms (or the positive end of a polar molecule) with the negative charge of the oxygen atom. Around negatively charged atoms or molecules, water places the positive hydrogen atoms first. Look at the difference in the spacing between water and positive or negative atoms. Around the sodium atom, the positive hydrogen atoms are still free to bind with other atoms. However, in the case of chlorine, the packing of the atoms is tighter. The arrangement of water molecules around any other atom or molecule leads to differences in water's ability to dissolve a substance. Hence, some things are easier to dissolve in water than others. Thanks to this property, water is termed as the universal solvent. It is due to these special properties that water is an indispensable and inevitable need of the planet. FORMS OF WATER: Water occurs in various forms such as lakes, groundwater, clouds etc. With water taking such diverse forms, it is essential to understand systematically the various forms of water

WATER

SURFACE

Fresh Water (L) Marine Water (L) Glaciers (S)

G- Gas, L – Liquid, S- Solid

SUB - SURFACE

Aquifers (L) Aquicludes (L) Aquifuges (L)

ATMOSPHERIC

Clouds (G) Precipitation (L)

WATER AS AN ENVIRONMENTAL COMPONENT: Water is an important environment component and performs the following functions 1. Source of nutrition and energy to all living organisms 2. Maintains temperature throughout the globe 3. It is a medium for living and movement of organisms

AIR In this topic, we need to have a basic knowledge of air in the perspective that it is an environment component. We will cover the following for the environment component “water” •

Air and Atmosphere

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Air Composition

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Layers of Atmosphere

•

Air as an Environment Component

AIR AND ATMOSPHERE: Air is a homogeneous mixture of gases present all over the earth that is essential for breathing, maintains heat balance of earth and stabilizes climate. The cover of air or layer that envelops the earth is known as atmosphere. AIR COMPOSITION: Air is a mixture of 18 gases which can be listed as below in terms of % in volume of air. S.No. GAS % by Volume 1 Nitrogen 78.09 2 Oxygen 20.95 3 Argon 0.93 4 Carbon di oxide (NO2) 0.032 5 Neon 0.0018 6 Helium 0.00052 7 Methane 0.00015 8 Krypton 0.00010 9 Hydrogen 0.000052 10 Nitrogen two oxide (N2O) 0.000021 11 Carbon monoxide (CO) 0.000011 12 Xenon 0.000008 13 Ozone 0.000002 14 Ammonia 0.0000006 15 Nitrogen di oxide (NO2) 0.0000001

16 17 18

Nitric Oxide (NO) Sulphur di oxide (SO2) Hydrogen Sulphide (H2S)

0.00000006 0.00000002 0.00000002

It would be a tough task for you to memorise all these components with their percentages. The student is expected to have a fair knowledge by understanding the composition and able to put forth a minimum the five major gas with percentage. LAYERS OF ATMOSPHERE: The atmosphere is divided into several distinct spherical layers, or strata, separated by narrow transition zones. The study of these layers is called aeronomy. The temperature structure of the atmosphere of the planet behaves in a manner dependent upon the balance between heating from the sun's incoming radiation, heating from the surface below, and properties inherent to the gases of the atmosphere itself. Each atmospheric layer is characterized by differences in chemical composition that produce variations in temperature. The upper boundary at which gases disperse into space extends to several hundred kilometers above sea level. The layers are depicted in the following diagram.

The troposphere is the atmospheric layer closest to the planet and contains the largest percentage of mass of the total atmosphere. It is characterized by the density of its air and

an average vertical temperature change of approximately 6 degrees Celsius per kilometer. In this layer temperature and water vapour composition decrease rapidly with altitude. Water vapour is important in regulating air temperature because it absorbs solar energy and thermal radiation from the planet's surface. The upper boundary of the troposphere ranges in height from 8 km in high latitudes, to 18 km above the equator. Its height also varies with seasonal changes; it is highest in the summer and lowest in the winter. A narrow zone called the tropopause separates the troposphere from the next highest layer called the stratosphere. Air temperature within the tropopause remains constant with increasing altitude. The stratosphere is the second major layer of air in the atmosphere. It resides between 10 and 50 km above the planet's surface. The air temperature in the stratosphere remains constant up to an altitude of 25 km. It then increases gradually to 200-220 degrees Kelvin at the lower boundary of the stratopause, which is marked by a decrease in temperature. Air temperatures increase with altitude in the stratosphere, which has a stabilizing effect on atmospheric conditions. Ozone plays the major role in regulating temperature. Temperatures increase as the ozone concentration increases. Solar energy is converted to kinetic energy when ozone molecules absorb ultraviolet radiation in heating the stratosphere. The mesosphere extends from approximately 50 km to 80 km. It is characterized by decreasing temperatures, which register at about 190-180 K and at an altitude of 80 km. Because there are decreased concentrations of ozone and water vapor, the temperature is lower than in the troposphere or stratosphere. The thermosphere is located right above the mesosphere, separated by the mesopause. The temperature in the thermosphere increases with altitudes up to 1000-1500 K. The increase in temperature is due to the absorption of intense solar radiation by the remaining molecules of oxygen. The exosphere is the most distant atmospheric layer. It extends to about 9601000 km. It is a transitional zone between earth's atmosphere and interplanetary space. AIR AS AN ENVIRONMENTAL COMPONENT: As an environmental component, air performs the following functions.

(i) (ii) (iii) (iv)

It is a store house/carrier of oxygen and enables respiration. It is a medium for sound and light propagation It absorbs the harmful radiations of the sun It stabilizes weather and climate

LAND Land (or) Lithosphere refers to the solid layers of rock material on the earth’s surface, both on the continents and ocean floors. The lithosphere is composed of the crust, mantle and upper/inner layers. The average thickness of lithosphere is about 100 km. The crust is thicker in the continents than on the ocean floors. The crustal layer is of lighter density compared to the interior layers. As the crustal layer comprises of rocks rich in silica and aluminium, it is called the sial layer. Below the sial layer lies the mantle which consists of (a) Inner silicate or sima layer having materials rich in silica and magnesium, and (b) transitional zone of mixed metals and silicates. The core of the earth consists of metals in liquid or plastic state because of high temperature and pressure. The core of the earth has a radius of about 3400 km. As nickel and iron are dominant in the core, it is called Nife. This accounts for earth’s magnetism. In case of land, two things are of utmost importance and they determine the value of thal land. They are (1) rocks that are found above the land level and (2) soil that is below the ground level Rock can be defined as a hard material on the earths crust often exposed on the sources which contains minerals within them. There are three types of rocks. Igneous Rocks: These rocks are formed by colling of molten magma. Quartz, Felspar and mica are few examples Sedimentary Rocks: This type of rock is formed by deposition of weathered minerals which are derived from igneous rocks. Clay, quartz, iron oxides, calcium carbonate are some examples. Metamorphic Rocks: This type of rock is formed by heat and pressure. Quartz, clay, calcite etc are of this type.

Soils are a mixture of inorganic and organic minerals; the soils are derived from some parent material. The inorganic part of the soil is formed from rock by fragmentation or weathering, while organic components of soil are formed by decomposition and other natural processes.

ROLE OF LAND (1) It is the platform that enables the establishment and movement of living organisms (2) It is the source to minerals, elements and food production

INTER RELATIONSHIP BETWEEN COMPONENTS Air, water and land interact and the vice versa is essential and is the essence of all activities that take place. In other words, the four spheres – atmosphere, lithosphere, hydrosphere and biosphere – interact among themselves. This can be depicted by the following diagram. There are two kinds of interactions: 1. Interaction between man and environment

2. Interaction between other organisms and environment There is a vital difference between these two interactions. The organisms adapt themselves to the environments while man modifies environments to suit themselves. It would be binding to restrict our study to the relationship between man and environment. Man is a part of the biosphere. In the early periods of human history, human beings were just like any other animal being entirely dependent on the environment. Food gathering, hunting and fishing could not sustain a large population. With the development of agriculture food was available in abundance and permanent settlements came into existence. Mining of coal, iron and other minerals heralded the Industrial Revolution. These led to the increased production from fields and factories, and the colonization of new landmasses. With the tools at his command, man became a master of the environment. Man’s activities were aimed at satisfying his increasing needs from the environment. With rapid increase in human population during the last 100 years, his needs have increased enormously leading to an adverse impact on the physical and biological environment. Environmental pollution has taken place on a large scale in industrial and urban areas. These environmental changes pose a threat to survival of man on the earth. Raw materials and energy are derived from the environment and useful products are obtained by using “technology”. This process leads to production of wastes which are returned to nature causing pollution. A key aspect of environmental science is the “interrelatedness” of things, the influence that one thing, action, or change may have on another living organisms and the aspects of the environment pertaining directly to them are called biotic, and other portions of the environment are abiotic. There are strong interactions among living organisms and the various spheres of the abiotic environment. To a large extent these are best described by cycles of matter that involve biological, chemical, and geological processes and phenomena. Such cycles are called biogeochemical cycles. Ecology is the science that deals with the relationships between living organisms with their physical environment and with each other3. Ecology can be approached from the viewpoints of (I) the environment and the demands it places

on the organisms in it or (2) organisms and how they adapt to their environmental conditions. An ecosystem consists of an assembly of mutually interacting organisms and their environment in which materials are interchanged in a largely cyclical manner. An ecosystem has physical, chemical, and biological components along with energy sources and pathways of energy and materials interchange. Thus an understanding of ecology and ecosystem is essential in the management of modern industrialized societies in ways that are compatible with environmental preservation and enhancement. This aspect is addressed in the forthcoming chapters. SUBCOMPONENTS There is widespread confusion over the terms sub components of environment. While some people interpret the following sub components as additional components to air, water and land, there are a few people who say that it is a term that refers to the sub divisions of the components air, water and land. As per the first school of thought, the following are sub components of environment 1. Light 2. Temperature 3. Sound Going by sub components (sub divisions) of water, air and land we have the following Sub Components of Water Rivers Lakes Rain Glaciers Seas Oceans Ground Water Sub Components of Land Mantle

Crust Inner Layer Outer Layer Sub Components of Air Tropospheric Air Stratospheric Air Mesospheric Air Exospheric Air

From the study of former question papers, it is established that the University subscribes to the sub components of water, sub components of air and sub components of land. Therefore the students are requested to follow that school of thought.