Expected impacts of global warming:

Expected impacts of global warming – would certainly be very harmful and dangerous:

A large body of scientific studies, exhaustively reviewed, has produced a long list of possibilities of impacts of global warming. Nobody can say that any of the items on the list are certain to happen. But most of the climate experts agree that the impacts listed below are more likely to happen. The exact timings, for them, are difficult to predict, but they are in the opinion that, if humanity manages to begin restraining its emissions within the next few decades, so that greenhouse gases do not rise beyond twice the pre-industrial level (we are already 35% above it and rising each year, at an accelerating rate) the consequences would certainly be very dangerous - probably including a radical reorganization and impoverishment of many of the ecosystems that sustain our civilization. Expected impacts are:

(1) Most places will continue to get warmer, especially at night and in winter. The temperature change will benefit some regions, at least for a time, while harming others like, patterns of tourism will shift. The warmer winters will benefit health in some areas, but globally, mortality will rise due to summer heat waves and other effects.

(2) Sea levels will continue to rise for many centuries. The last time the planet was 3°C warmer than now, the sea level was roughly 5 meters higher. That submerged coastlines where many millions of people now live. Also, storm surges will cause emergencies.

(3) Weather patterns will keep changing, probably toward an intensified water cycle with stronger floods and droughts. Most regions that are now subject to droughts are expected to get drier (because of warming as well as less precipitation), and most wet regions will get wetter. Changes in extreme weather events are hard to predict, but in some regions storms with more intense rainfall are liable to bring worse floods. Mountain glaciers and winter snowcap will shrink, jeopardizing many water supply systems. Each of these changes has already begun to happen in some regions.

(4) Ecosystems will be stressed, although some managed agricultural and forestry systems will benefit, at least in the early decades of warming. Uncounted valuable species, especially in the Arctic, mountain areas, and tropical seas, must shift their ranges. Many that cannot will face extinction. A variety of pests and tropical diseases are expected to spread to warmed regions. Each of these problems has already been observed in numerous places.

(5) Increased carbon dioxide levels will affect biological systems independent of climate change. Some crops will be fertilized, as will some invasive weeds (the balance of benefit vs. harm is uncertain). The oceans will continue to become markedly more acidic, gravely endangering coral reefs, and probably harming fisheries and other marine life.

(6) There will be significant unforeseen impacts. Most of these will probably be harmful, since human and natural systems are well adapted to the present climate.

Water pollution, its prevention and control:

Water pollution, its prevention and control:

Water is a key resource for our quality of life. It also provides natural habitats and eco-systems for plant and animal species. Access to clean water for drinking and sanitary purposes is a precondition for human health and well-being. Clean unpolluted water is essential for our ecosystems. Plants and animals in lakes, rivers and seas react to changes in their environment caused by changes in chemical water quality and physical disturbance of their habitat.

Water pollution is a human-induced change in the chemical, physical, biological, and radiological quality of water that is injurious to its existing, intended, or potential uses such as boating, waterskiing, swimming, the consumption of fish, and the health of aquatic organisms and ecosystems. Thus, the discharge of toxic chemicals from a pipe or the release of livestock waste into a nearby water body is considered pollution. The contamination of ground water, rivers, lakes, wetlands, estuaries, and oceans can threaten the health of humans and aquatic life.

Contaminants have a significant impact on aquatic ecosystems. for example, enrichment of water bodies with nutrients (principally nitrogen and phosphorus) can result in the growth of algae and other aquatic plants that shade or clog streams. Direct exposures to toxic chemicals such as pesticides, is also a health concern for individual aquatic plants and animals. Without healthy water for drinking, cooking, fishing, and farming, the human race would perish. Clean water is also necessary for recreational interests such as swimming, boating, and water skiing.

A. Sources of Water Pollution: Sources of water pollution are generally divided into two categories. The first is point-source pollution, in which contaminants are discharged from a discrete location. Sewage outfalls and oil spills are examples of point-source pollution. The second category is non-point-source or diffuses pollution, referring to all of the other discharges that deliver contaminants to water bodies.

Numerous manufacturing plants pour off undiluted corrosives, poisons, and other noxious byproducts to water streams. The construction industry discharges slurries of gypsum, cement, abrasives, metals, and poisonous solvents. The mining industry also presents persistent water pollution problems. In yet another instance of pollution, hot water discharged by factories and power plants causes so-called ‘thermal pollution’ by increasing water temperatures. Such increases change the level of oxygen dissolved in a body of water, thereby disrupting the water's ecological balance, killing off some plant and animal species while encouraging the overgrowth of others. Towns and municipalities are also major sources of water pollution.

In many public water systems, pollution exceeds safe levels. One reason for this is that much groundwater has been contaminated by wastes pumped underground for disposal or by seepage from surface water. When contamination reaches underground water tables, it is difficult to correct and spreads over wide areas. Discharge of untreated or only partially treated sewage into the waterways threatens the health of their own and neighboring populations as well. Along with domestic wastes, sewage carries industrial contaminants and a growing tonnage of paper and plastic refuse. Although thorough sewage treatment would destroy most disease-causing bacteria, the problem of the spread of viruses and viral illness remains. Additionally, most sewage treatment does not remove phosphorus compounds, contributed principally by detergents.

B. Dangers of Water Pollution: Virtually all water pollutants are hazardous to humans as well as lesser species; sodium is implicated in cardiovascular disease, nitrates in blood disorders. Mercury and lead can cause nervous disorders. Some contaminants are carcinogens. DDT is toxic to humans and can alter chromosomes. Along many shores, shellfish can no longer be taken because of contamination by DDT, sewage, or industrial wastes.

C. Prevention and Control of Water Pollution: Sewage should be treated before it is discharged into the river or ocean. This is possible through modern techniques.

Sewage is first passed through a grinding mechanism. This is then passed through several settling chambers and neutralized with lime. Up to this stage, the process is called primary treatment. The sewage still contains a large number of pathogenic and non-pathogenic organisms, and also sufficient quantity of organic matter. The neutralized effluents are sent to UASB (up-flow anaerobic sludge blanket). It is a reactor. In this, the anaerobic bacteria degrade the biodegradable material present in the waste water. This removes foul odor and releases methane, which can be used elsewhere. In this system, the pollution load is reduced upto 85 percent. After this, water is sent to aeration tanks where it is mixed with air and bacteria. Bacteria digest the organic waste material. This is called biological or secondary treatment. Even after the treatment, water is not yet fit for drinking. The harmful microorganisms need to be killed. The final step (tertiary treatment) is, therefore, a disinfection process, to remove final traces of organics, bacteria, dissolved inorganic solids, etc. For tertiary treatment, methods, such as chlorination, evaporation, and exchange absorption may be employed. These depend upon the required quality of the final treatment.

Apart from the above, you should also adopt the following practices:

(i) Waste food material, paper, decaying vegetables and plastics should not be thrown into open drains.

(ii) Effluents from distilleries, and solid wastes containing organic matter should be sent to biogas plants for generation of energy.

(iii) Oil slicks should be skimmed off from the surface with suction device. Sawdust may

be spread over oil slicks to absorb the oil components.