污染是在我们的环境中的不受欢迎的变化对植物，动物和人类产生有害影响的影响。这种情况发生时，只有短期的生态效益，在长期的生态效益为人类的成本。在过去的几十年里，我们已经污染了我们的空气、水和土地，生命本身就取决于各种各样的废物。
从生态角度来看，污染物可分为可降解或非持久性污染物可迅速分解的自然process.eg：生活污水、废弃的蔬菜等，或是缓慢降解持久性有机污染物的污染物留在环境中许多年不变的条件和需要几十年或更长的时间才能降解。例如：DDT（农药）和大多数塑料。不可降解的污染物不能通过自然过程退化。一旦被释放到他们的环境很难根除，继续accumulate.eg：有毒元素如铅、汞和核废物。
Pollution is the effect of undesirable changes in our surroundings that have harmful effects on plants, animals and human beings. This occurs when only short term ecological gains are made at the cost of long term ecological benefits for humanity. During the last few decades we have polluted our air, water and land on which life itself depends with a variety of waste products.
From an ecological point of view, pollutants can be classified as degradable or non-persistent pollutants which can be rapidly broken down by natural process.eg: domestic sewage, discarded vegetables etc., Slowly-degradable or persistent pollutants are pollutants that remain in the environment for many years in an unchanged condition and take decades or longer to degrade.eg:DDT(pesticides) and most plastics. Non-degradable pollutants cannot be degraded by natural processes. Once they are released into the environment they are difficult to eradicate and continue to accumulate.eg: toxic elements like lead or mercury and nuclear wastes.
Pollution is a very wide topic. This thesis focuses on two major pollutions- air and water, and explains in detail the causes, effects and control measures.
Air pollution occurs due to the presence of undesirable solid or gaseous particles in the air in quantities that are harmful to human health and the environment. The air may become polluted by natural causes such as volcanoes, which release ash, dust, sulphur and other gases, or by forest fires that are occasionally caused by lightening. However, unlike pollutants from human activity, naturally-occuring pollutants tend to remain in the atmosphere for a short time and do not lead to permanent atmospheric change.
Air pollution began to increase in the beginning of the twentieth century with the development of transportation systems and large-scale use of petrol and diesel. These severe air quality problems due to the formation of petrochemical smog from the combustion residues of diesel and petrol engines were felt for the first time in Los Angeles. Pollution due to auto- exhaust remains a serious environmental issue in many developed and developing countries, including, India.
The air pollution control act in India was passed in 1981 and the motor vehicle act for controlling air pollution was passed very recently. These laws are intended to prevent the air from becoming over polluted.
The greatest industrial disaster leading to serious air pollution took place in Bhopal, where the extremely poisonous methyl isocyanides gas was accidently released from the Union Carbide’s pesticide manufacturing plant, on the night of December 2, 1984. The effects of this disaster on human health and the soil are felt even today.
Lead is a major air pollutant that remains largely unmonitored and is emitted by vehicles. High lead levels have been reported in the ambient air in metropolitan cities. Leaded petrol is the primary source of air-borne lead emissions in Indian cities. The use of unleaded petrol is one way of reducing this pollutant. Pollutants are also found indoors from the infiltration of polluted outside air and from various chemicals used or produced inside buildings.
The effects of air pollution on living organisms are adverse. Cigarette smoking is responsible for the greatest exposure to carbon monoxide. Exposure to air containing even 0.001% of carbon monoxide for several hours can cause coma and even death. Sulphur dioxide irritates the respiratory tissues; chronic exposure to it causes a condition similar to bronchitis. The acids can become attached to particles which, when inhaled, are very corrosive to the lungs.
The widely talked changes in the ozone layer have serious implications for mankind. The effects on human health due to increased UV radiation are sunburn, cataract, aging of the skin and skin cancer. It weakens the immune system by suppressing the body’s resistance to certain infections like measles, chickenpox and other viral diseases that elicit rash and parasitic diseases like malaria introduced through the skin.
UV rays also affect the ability of plants to capture light energy during the process of photosynthesis. This reduces the nutrient content and the growth of plants. This is seen especially in the case of legumes and cabbage.
Air pollution can be controlled by two fundamental approaches: preventive techniques and effluent control. One of the effective means of controlling air pollution is to have proper equipment in place. This includes devices for removal of pollutants from the flue gases through scrubbers, closed-collection recovery systems, and the use of dry and wet collectors, filters, electrostatic precipitators and so on. Building higher smoke-stacks facilitates the discharge of pollutants as far away from the ground as possible. Industries should be carefully located so as to minimize the effects of pollution after considering the topography and the wind directions. The substitution of raw materials that cause more pollution with those that cause less pollution will also help.
Water pollution is when the quality or composition of water changes directly or indirectly as a result of man’s activities such that it becomes unfit for any purpose it is said to be polluted. Point sources of pollution are when a source of pollution can be readily identified because it has a definite source and place where it enters the water it is said to come from a point source. E.g.: municipal and industrial discharge pipes. Non-point sources of pollution are when a source of pollution cannot be readily identified, such as agricultural runoff, acid rain etc.,
There are several classes of common water pollutants. These are disease – causing agents which include bacteria, viruses, protozoa and parasitic worms that enter water from domestic sewage and untreated human and animal wastes. Large amounts of human waste in water increases the number of these bacteria, which cause gastrointestinal diseases. Other potentially harmful bacteria from human wastes may also be present in smaller numbers. Thus, the greater the amount of wastes in the water, the greater is the chance of contracting diseases.
The third class of pollutants is inorganic plant nutrients. These are water -soluble nitrates and phosphates that cause the excessive growth of algae and other aquatic plants. The quantity of fertilizers applied in a field is often many times more than actually required by plants. The chemicals in fertilizers and pesticides pollute both soil and water.
A fourth class of water pollutants is water- soluble inorganic chemicals, which are acids, salts and compounds of toxic metals such as mercury and lead. High levels of these chemicals can make the water unfit to drink, harm fish and other aquatic life, reduce crop yields and accelerate the corrosion of equipment that is in contact with this water.
Another cause of water pollution is a variety of organic chemicals, which includes oil, gasoline, plastics, pesticides, cleaning solvents, detergents and many other chemicals. These are harmful to aquatic and human health. They enter the water directly from industrial activity, either from improper handling of chemicals in industries and usually from the improper and illegal disposal of chemical wastes.
The foremost necessity of controlling water pollution is prevention. On the other hand, setting up effluent treatment plants to treat wastes can reduce the pollution load in the recipient water. The treated effluent can be reused for either gardening or cooling purposes, wherever possible. A few years ago a new technology, called the Root Zone Process has been developed by Thermax. This system involves running contaminated water through root zones of specially-designed reed beds.
To conclude, the responsibility to prevent pollution lies in the hands of every individual. Some concepts that help individuals contribute towards a better quality of our environment and human life are:
Try to plant trees wherever you can and more importantly take care of them. They reduce air pollution.
From the mail you receive reuse as many envelopes as you can.
Use pesticides in your home only when absolutely necessary and use them in small amounts. Some insect species help to keep a check on the populations of pest species.
Reduce the use of fossil fuels by either walking short distances or using a car pool, sharing a bike or using public transport. This reduces air pollution.
Shut off the lights and fans when not needed.
Do not use aerosol spray products and commercial air-fresheners. They damage the ozone layer.
Do not pour pesticides, paints, solvents, oil or other products containing harmful chemicals down the drain or onto the ground.
Buy consumer goods in refillable glass containers instead of cans or throwaway bottles.
Try to avoid asking for plastic carry bags when you buy groceries or vegetables or any other items. Use your own cloth bag instead.
Set up a compost bit in your garden to produce manure and reduce use of fertilizers.