Explain the cause and effects of ozone depletion, global warming and acid rain. State the role of individual in overcoming these problems.
Ozone depletion refers to a lowered
concentration of ozone in the upper atmosphere. Evidence has been found that air
pollutants, leading to the formation of “holes”, can damage the ozone layer. Today,
scientists have discovered holes in the ozone layer over the
Recent studies show that the ozone hole has been formed due to chemical effects. Since ozone is formed and broken down continuously in natural processes, the rate of breakdown can be speeded up by the presence of ozone depletion pollutants such as chlorofluorocarbon compounds, halons and bromine. CFC compounds may drift up to the upper atmosphere and are involved in chlorine-releasing reactions. The chlorine radical is released from CFC compounds and reacts with an ozone molecule in the presence of sunlight. As a result, the ozone molecule is destroyed and forms a chlorine monoxide radical. When CIO reacts with a free oxygen radical, another CI radical is released. this CI radical can then attack another ozone molecule.
The destruction of the ozone layer results in a significant increase in ultraviolet radiation reaching the Earth’s surface. It may induce various adverse effects on humans. It has direct fects on DNA. It can modify the genetic information in body cells. It will increase the incidence of skin cancer, cataract and lung diseases, as well as a reduction in the function of the immune system. Also it will reduce the yields of crop and disrupt the ecological balance of food webs. Photochemical smog will increase because of the increase in ultraviolet radiation.
Global
warming refers to the gradual increase in the average temperature in the
atmosphere as a result of the accumulation of greenhouse gases. The increase in
concentration of greenhouse gases in the atmosphere slows down the heat loss
from the earth to the space. As a result, the atmosphere is warming up. This
leads to changes in climate and other subsequent effects on the earth.
The warming effect of carbon dioxide, water vapour and other gases has been named the greenhouse effect. There is more water in the atmosphere than carbon dioxide, so most of the greenhouse heating of the earth's surface is due to water vapour. However, there is a gap in the absorption by water vapour (i.e, certain wavelength of infrared radiation cannot be absorbed by water vapour), which is partly plugged by carbon dioxide. If the amount of carbon dioxide increase, more heat will be trapped, and the earth will be warmed up more. This overheating problem is known as global warming. The water vapour content in the atmosphere, on the whole, is kept into a roughly constant level, while the carbon dioxide content in the atmosphere of the earth has been raising since the Industrial Revolution in Europe. Before the Industrial Revolution, the carbon dioxide concentration was about 280-90 part per million; in 1990, it was about 340 part per million. The warming up of the earth is not only due to the increase in the amount of carbon dioxide in the atmosphere, but also due to other gases. Since carbon dioxide's influence contribute most to this global warming, so, when we talking about Greenhouse effect, we will mainly discuss about carbon dioxide. Though the concentration of other greenhouse gases are present in a much lower level than carbon dioxide, they are much more efficient at absorbing infrared radiation, and have a potentially greater influence on the greenhouse effect.
Apart from warming up the earth, it may also cause flooding to the low-lying land. Although greenhouse effect may cause flooding, without its influence, the earth's surface will at an average of -18°C rather then 15°C .
Global
warming will cause rising global temperatures are expected to raise sea level,
and change precipitation and other local climate conditions. Changing regional
climate could alter forests, crop yields, and water supplies. It could also
affect human health, animals, and many types of ecosystems. Deserts may expand
into existing rangelands, and features of some of our National Parks may be
permanently altered.
Most of the United States is expected to warm,
although sulfates may limit warming in some areas. Scientists currently are
unable to determine which parts of the United States will become wetter or
drier, but there is likely to be an overall trend toward increased
precipitation and evaporation, more intense rainstorms, and drier soils.
Unfortunately, many of the potentially
most important impacts depend upon whether rainfall increases or decreases,
which can not be reliably projected for specific areas
Individuals
should recognize that collectively they could make a difference. Think back to
the days before recycling became popular – when everyone threw everything out
in the trash. In less than 20 years, most households have gone from recycling
little to nothing to recycling newspapers, plastics, glass and metal. Many
businesses recycle paper and buy recycled products and many industries practice
source reduction in their packaging efforts. An entire mindset has changed in
one generation!
Taking action on global warming (or
climate change) is similar. In some cases, it only takes a little change in
lifestyle and behavior to make some big changes in greenhouse gas reductions.
For other types of actions, the changes are more significant. When the 270
million people in the U.S. or the 6 billion people worldwide multiply that
action, the savings are significant.
"Acid rain" is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry. Wet deposition refers to acidic rain, fog, and snow. As this acidic water flows over and through the ground, it affects a variety of plants and animals. The strength of the effects depend on many factors, including how acidic the water is, the chemistry and buffering capacity of the soils involved, and the types of fish, trees, and other living things that rely on the water. Dry deposition refers to acidic gases and particles. About half of the acidity in the atmosphere falls back to earth through dry deposition. The wind blows these acidic particles and gases onto buildings, cars, homes, and trees. Dry deposited gases and particles can also be washed from trees and other surfaces by rainstorms. When that happens, the runoff water adds those acids to the acid rain, making the combination more acidic than the falling rain alone.
Prevailing winds blow the compounds
that cause both wet and dry acid deposition across state and national borders,
and sometimes over hundreds of miles.
Scientists discovered, and have confirmed, that sulfur dioxide (SO2) and
nitrogen oxides (NOx) are the primary causes of acid
rain. In the US, About 2/3 of all SO2 and 1/4 of all NOx
comes from electric power generation that relies on burning fossil fuels like
coal.
Acid rain occurs when these gases
react in the atmosphere with water, oxygen, and other chemicals to form various
acidic compounds. Sunlight increases the rate of most of these reactions. The
result is a mild solution of sulfuric acid and nitric acid.
Individuals can contribute directly by conserving energy, since energy
production causes the largest portion of the acid deposition problem. For
example, you can turn off lights, computers, and other appliances when you are
not using them. Use energy efficient appliances: lighting, air conditioners,
heaters, refrigerators, washing machines, etc. Only use electric appliances
when you need them. Keep your
thermostat at 68 F in the winter and 72 F in the summer. You can
turn it even lower in the winter and higher in the summer when you are away
from home. Insulate your home as best you can. Carpool, use public
transportation, or better yet, walk or bicycle whenever possible
Buy vehicles with low NOx emissions, and maintain all vehicles well.
Be well informed.
To make the Earth cleaner and make us healthier, we are responsible to do these actions to protect our world.