Tuesday, May 31, 2011

PCB (Poly Chlorinated Biphenyl) Pollution


                PCBs or in other words, polychlorinated biphenyls are widely used as organic compounds and as dielectric fluids in transformers and capacitors. PCBs are organic compounds that contain 1-10 chlorine atoms attaché to biphenyl group (C12H10-xClx) and they are formed by electrophilic chlorination of biphenyl with chlorine gas. PCBs or Polychlorinated biphenyls were first commercially used in 1929 as a “safer” cooling and as an insulating fluid in electrical industry.

                These PCBs are not only used as coolants and insulating fluid but they are also used as components in early light fittings and in electrical transformers. Besides all these usages, PCBs are also used as plasticizers in paint and cement, as stabilizing additives in flexible PVC coating, in electrical wiring and in electronic components. Since PCBs have high viscosity, high flashing point and high thermal conductivity they can be used for cutting oils, as reactive flame retardants, lubricant oils, hydraulic fluids and sealants. And PCBs are organic compounds that contain Chlorine in it and therefore can also be used as pesticide.

Tuesday, May 24, 2011

Greenhouse effect and Global warming

Global warming is one of the worst environmental problems that the modern world is facing due to several unfavorable human behaviors. According to scientists and scientific research, global warming increases the average temperature of the earth’s near surface, air and the ocean. As a result of global warming unwonted environmental effects take place, such as the rise of sea level which causes several problems to small islands like Maldives islands.  Because of the global warming, there can be changes in the amount of precipitation, extreme weather conditions like droughts and heat waves.  And also global warming can affect the biodiversity of the world by eliminating animal and plant species due to the shifting of the temperature.
For this worst environmental effect, the main reason is the human activities. For instance, after the industrial revolution, people started to use more fossil fuels which gave rise to greenhouse gases. These greenhouse gases lead to a natural phenomena called greenhouse effect, which helps us live in a warmer place or on the other hand which warms the earth beyond its effective temperature. Without greenhouse effect the earth surface will be much cooler than what we are experiencing today.

Saturday, May 21, 2011

Climatic Changes



            Climate basically includes changes in temperature, humidity, atmospheric pressure, wind, precipitation of that place from a long period of time, whereas weather is the present condition of these elements.  And we all know that climate is changing from place to place, since climate is affected by the latitude, terrain, altitude and the nearby water bodies. Therefore, we can say that climate is a prediction made by observing the weather of a place for a long period of time; these predictions of climate, are very important to human life because the distribution of natural resources like forest/ vegetation depends on the climatic factors. Therefore, even a slight change in the climate can influence human life at a greater degree.
             Climatic changes are long term changes in the statistical distribution of weather patterns over period of time that range from decades to millions of years. The United Nations framework conversion on climatic changes defines climatic changes as “A change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”.  Climatic changes occur mainly due to the human behaviors that destroy the environment. Other than that, variation of solar radiation, deviation in the earth orbit, mountain building and continental drift contribute to the present undesirable climatic changes like extreme weather conditions.