Lifelong Learning Programme

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Chemistry is all around us
Copyright 2014
This project has been funded with
support from the European Commission

Educational Packages

Chemistry and Environment

Environmental chemistry, chemistry in environment and the human role

Introduction

A large number of people seem to regard chemical industry products as environmental pollutants. Over the last few decades more and more environmentally friendly materials and products have been realsed with considerably lower impact on environment as such. The relationship between industrial processes and environment has been more clearly defined which in turn calls for invention of novel chemical engineering technologies that are less harmful to natural environment.Another evident ecological demand is for updating relevant legislature on national and international level- a process that should go hand in hand with investments in science and technology.

1. Environmental components
The three components of environment are hydrosphere, atmosphere and lithosphere.

1.1. Hydrosphere ( from Greek hydro meaning “water”) comprises all waters contained on the Earth including oceans , seas, rivers ,lakes, dam lakes, swamps glaciers, underground waters and water in the atmosphere. Earth is the only planet in the Solar system on which there is water in liquid state. This water covers 71 % of Earth’s surface (97,5 % of water being saline and 2,5 % — freshwater). About 67,8 % of all fresh water is contained in the glaciers.

1.2. Atmosphere is the gaseous wrapping of our planet’s globe. This term is of Greek origin “atmos” meaning vapour and “sphere” meaning ball. Its function is to protect living organisms by preventing a large portion of ultraviolet rays from falling on them. The gaseous wrapping of the Eareth is called “air” and about 99 % of gasses are nitrogen and oxygen. Atmosphere can be regarded as being made up of five major layers called “spheres”: troposphere, stratosphere, mesosphere, thermosphere and exosphere; their designations being closely related to their location.

Earth’s atmosphere is 20000 km in height and at this altitude atmospheric air density equals the density of gases which fill up interplanetary space however, 90 % of its total mass is concentrated within the 15 kilometer overground layer. Atmosphere gradually dissolves in space.

With regard to its physical properties atmosphere is not homogeneous and uniform both in vertical and horizontal direction. With greater altitudes its content changes along with some other propereties and parameters.

Air which forms earth’s atmosphere is a mechanical mixture of different gases which do not interact with each other. Air content which is closer to earth’s surface is accurately determined. Apart from the major gases such as nitrogen, oxygen and argon there are some other gaseous admixtures of lower concentration. Nitrogen and oxygen are prevalent within the latitude of 800km. At an altitude above 400 km the content of lighter gasses starts to increase; helium being in the beginning, followed by hydrogen. Above altitude of 800km atmosphere contains mainly hydrogen.

1.3. Lithosphere. Soil. Lithosphere is another term of Greek origin meaning “stone” and “ball”. Lithosphere makes up the uppermost hard cover of our planet. It includes earth’s crust plus the upper layers of the mantle which are located above the asthenosphere. With regard to its physical-mechanical properties, lithosphere is strong, brittle and elastic layer which is able to withstand enourmous pressure up to 1 kbar.

Its thickness varies between 50-120 km reaching 300km at certain places. Lithosphere is severed at narrow elongated zones which, given the present day relief, correspond to the main active tectonic zones. The rest of its substance is unbroken and makes up separate thin blocks some of which are of gigantic dimensions and are referred to as plates. Laterally, and with regard to their physical and mechanical properties these plates are of extreme hardness, they are brittle and posses great strength against shear forces.

The uppermost layer of lithosphere is referred to as “soil”. It is a complex multiphase structural system at the surface of weatherized crust which posses the property of fertility. Soil is a mixture of minerals, organic matter and water of various content and ratio. It is capable of supporting life of plants on the earth surface. Soil is one of the key components of the chemical cycles occurring in the environment.One of the major cycles taking place in the soil is the ion exchange whereby a number of chemical elements such as K, Ca, Mg and others can reach plants. This property of soil determines its acidity – one of the most important factors behind the development of plants and micro-organisms.

2. Chemistry and environmental protection
The entire biosphere contains substances in concentrations which are variable. Poluution is available whenever these substances exceed predetermined permissible levels of concentration. The Environmental Protection Act defines “environmental pollution” as intrinsic change of its quality due to the impact of physical, chemical and biological factors caused by natural or human agent.

2.1. Air pollution. Atmosphere is regarded as polluted when it contains harmful gases, vapours, liquid or solid particles, including radioactive ones, which have a negative impact on living organisms and plants, bring about changes in climate, decrease visibility and incur material losses.

Pollution is a consequence of burning fossil fuels. Exhaust pollutants interact with moisture in atmosphere and form the so called acid rains. Raindrops are slightly acid due to the carbon dioxide in atmosphere, however nitrogen and sulphuric oxides proiduce stronger acids which have an unfavorable impact on plants and animals alike. The greater harm caused by carbon dioxide is seen in global warming, the so called green house effect which is said to be the reason for higher average temperatures on the planet. Another headache is the thinning of ozone layer which allows larger amounts of ultraviolet rays to reach the Earth.

2.2. Water pollution. Waste and sewer waters are the primary source of water pollution. Since the dawn of industrial revolution factories have been dumping their waste products in the water bodies which is detrimental to the development and growth of local flora and fauna. Households appear to be another big source of pollution as well as agriculture. Fertilizers which boost crops yield and pesticides used in prevention of vermines penetrate from soil into underground waters . Fresh water shortage is on the rise and one third of the world’s population suffer from such shortage

2.3. Soil pollution. The ecological functions of soil cover are found in its capacity to accumulate water supplies, nutrient elements, active organic substance and the chemical energy related to it; provide life support for plants and micro-organisms; regulate the chemical content of atmosphere, overground and underground waters and sustain geoecosystems.

Soil degradation includes: erosion, dehumification, acidization, salinification, secondary repacking of soils, seasonal overmoisturing, destroyed land surfaces; technogene contamination appears to be one of the major soil damages whereas the other degradation processes are related to different elements of environment. Degradation occurs as a consequence to burning, spraying with pesticides and dumping of industrial and household wastes and watering with polluted waters.

3. Global ecological effects produced by chemical processes in environment

3.1. Global warming (greenhose effect). Global warming is the unusually rapid increase in Earth’s average surface temperature over the past century primarily due to the greenhouse gases released by people burning fossil fuels. Greenhouse effect is a process whereby the infrared radiation of some atmospheric gases warms earth’s surface. Without this effect average temperature would have been -18°C (255 K) instead of 15°C (288 K). Such temperature makes it impossible for water to exist in liquid state hence there would be no oceans on Earth. Greenhouse effect is determined by atmospheric transparency in the visible and infrared zone.

The generic term “greenhouse gases” concerns all gases that cause the warming of Earth and the lower layers of atmosphere. Carbon dioxide allows sunrays to reach the surface of the planet but withholds the return of warmth. Other gases which act in the very same way are methane, nitrogen oxide, small quantities of which are obtained in burning fossil fuels and as product of agricultural activity; and freons which are used in sprayers and in air conditioning equipment.

3.2. Nuclear winter. This term designates a hypothetical state of global climate caused in the wake of a nuclear war .it is supposed that due to a large quantity of smoke and soot in the startosphere caused by the explosion of a great number of nuclear war heads, the temperature of our planet will sharply drop to arctic values since sunrays will be reflected by the upper layer of the atmosphere.

3.3. Smog. Smog is the mixture of smoke and fog. Initially, it was mainly a result from burning of enormous quantities of coal which caused oversaturation of air with smoke particles and sulphuric dioxide. Today smog is largely the product of automobile and industrial emissions which interact with sunrays in the atmosphere until the formation of secondary pollutants which in turn remix with the primary pollutants thus forming photochemical smog. Photochemical smog was first described in the 50s of the last century. It is the chemical reaction of sunlight with the oxides of nitrogen and various organic substances. The resultant mixture contains:
  • Nitrogen oxides
  • Tropospheric ozone
  • Volatile organic substances such as petrol vapours, pesticides
  • CH3COOONO2
  • aldehides


3.4. Acid rain. Energy production based on chemical fuels, mainly coal, is the top polluter of atmosphere. This is due to the fact that all chemical fuels contain sulfur. It is found mostly in coal as a remnant of organic matter or is of organic origin. In the organic matter it is found in the form of organic compounds containing sulphur. Hydrogen bisulphide is a product of organic matter decomposition which amounts to 100 million tons

Sulphur is also contained in crude oil. In atmosphere sulphur is found in the form of compounds such as hydrogen bisulphide, sulphur dioxide, sulphur trioxide. This gas is dissolved in cloud water drops and forms sulfuric acid. That is how acid rains are produced. Nitrous oxides formed by the impact of high temperature in internal combustion engines are constituent part of smoke gases and produce itrous acid which appears to be other components of rains.

Sulphur dioxide directly impacts plants penetrating through the sheath of the leaves and their pores. It is dissolved in the sap thus producing sulphates which are detrimental to living matter. Leaves lose their moisture then their chlorophyll, wither and die. More sensitive to SO2 are vegetables, cotton, alfalfa because their cell structure is directly destroyed and they die. In addition acid rains impair a number of other objects such as cultural assets made of marble and limestone aswell as steel structures.

3.5. Destruction of ozone layer. This is a depletion of steady and sustainable drop by 4% of overall ozone amount in the stratosphere every 10 years which started in the late 70s. It is accompanied by a larger, however seasonal, depletion of ozone in stratosphere over the poles regions. The latter phenomenon is known as ozone hole.

In the Antarctic region winter begins in March. Atmosphere gets cooler and the winds blowing at great altitudes commence their circulation around the continent whereby a barrier is built which does not allow air from northern latitudes to mix with the air from south latitudes. As a result clouds are formed which contain ozone and substances that are the product of human activity and destroy ozone. When south spring comes solar energy begins to warm atmosphere. This causes a chemical reaction between substances and the ozone molecules which is the cause for the destruction of the ozone layer. When Antarctic summer is on, the winds forming the barrier around the continent begin to abate and the air which is rich in ozone is transferred to the other side of Antarctica to fill up the depleted ozone layer. In this way the ozone hole usually disappears during November or December. Chlorfluorocarbones are found in aerozoles and coolants used in the manufacture of refrigerators and automobile radiators. During the mid 70s of the last century scientists discovered that CFCs are the main cause for ozone layer depletion; moreover CFCs are transferred by air stream thus reaching startosphere.

The full spectrum of UV-B, mainly type UV-B, could harm animal skin including human skin. Sunburn is the most evident and well known result from over-exposure to UV radiation. The latter may cause decolorization of skin, wrinkles and red brownish spots. UV rays type B may even kill the plant by interfering with the photo-synthetic processes. The cause is found in the mutation of important plant cells, interference with respiratory processes and the ability of the plant to absorb СО2 and produce О2.