If you've ever gotten a nasty sunburn, you've experienced the singeing effects of ultraviolet radiation from the sun. In fact, you probably made a personal vow to forever apply (and reapply) sunscreen on sunny days. Luckily, the earth shades us from the vast majority of intense ultraviolet light with its own sunscreen -- the ozonelayer. Without the ozone layer, we wouldn't just sunburn, there's a chance we'd go extinct. The sheer intensity of unadulterated ultraviolet sunlight would threaten most species that live on the surface of the earth.
The ozone layer gets its name from ozonegas, an allotrope, or form, of the element oxygen. Ozone gas has become so synonymous with the ozone layer that people now refer to the layer as "the ozone." However, ozone gas doesn't just coat our earth's stratosphere. It can be found on the earth's surface as well -- used for such things as bleaching, sterilizing water, and removing unpleasant smells from products.
Despite its name, the ozone layer isn't just ozone gas. Oxygen gas, another allotrope of oxygen, is abundant in the ozone layer, as well. Oxygen gas is essential for the creation of ozone gas, and it absorbs ultraviolet light, preventing that light from reaching the earth's surface. The ozone layer forms naturally in the stratosphere, where ozone and oxygen gas are always converting into each other -- continually "reapplying" the earth's sunscreen.
Scientists study the ozone layer to grasp its patterns of change and to determine how humans affect this change. If the ozone is suffering, how are we to blame? First, let's investigate what this layer really is.
Distance Makes the Heart Grow Fonder
It's pretty confusing when we hear about the dangers of ozone depletion one day and the need to reduce ozone the next. Ozone gas is extremely helpful -- but only when it's miles away from us in the ozone layer. When car exhaust and other things cause the production of ozone gas near the surface of the earth, it pollutes the air and causes health problems.
Coal is the dirtiest of all fossil fuels. When burned, it produces emissions that contribute to global warming, create acid rain and pollute water. With all of the hoopla surrounding nuclear energy, hydropower and biofuels, you might be forgiven for thinking that grimy coal is finally on its way out.
But coal is no sooty remnant of the Industrial Revolution -- it generates half of the electricity in the United States and will likely continue to do so as long as it's cheap and plentiful [source: Energy Information Administration]. Clean coal technology seeks to reduce harsh environmental effects by using multiple technologies to clean coal and contain its emissions.
Coal is a fossil fuel composed primarily of carbons and hydrocarbons. Its ingredients help make plastics, tar and fertilizers. A coal derivative, a solidified carbon called coke, melts iron ore and reduces it to create steel. But most coal -- 92 percent of the U.S. supply -- goes into power production [source: Energy Information Administration]. Electric companies and businesses with power plants burn coal to make the steam that turns turbines and generates electricity.
When coal burns, it releases carbon dioxide and other emissions in flue gas, the billowing clouds you see pouring out of smoke stacks. Some clean coal technologies purify the coal before it burns. One type of coal preparation, coal washing, removes unwanted minerals by mixing crushed coal with a liquid and allowing the impurities to separate and settle.
Other systems control the coal burn to minimize emissions of sulfur dioxide, nitrogen oxides and particulates. Wet scrubbers, or flue gas desulfurization systems, remove sulfur dioxide, a major cause of acid rain, by spraying flue gas with limestone and water. The mixture reacts with the sulfur dioxide to form synthetic gypsum, a component of drywall. Low-NOx (nitrogen oxide) burners reduce the creation of nitrogen oxides, a cause of ground-level ozone, by restricting oxygen and manipulating the combustion process. Electrostatic precipitators remove particulates that aggravate asthma and cause respiratory ailments by charging particles with an electrical field and then capturing them on collection plates.
Gasification avoids burning coal altogether. With integrated gasification combined cycle (IGCC) systems, steam and hot pressurized air or oxygen combine with coal in a reaction that forces carbon molecules apart. The resulting syngas, a mixture of carbon monoxide and hydrogen, is then cleaned and burned in a gas turbine to make electricity. The heat energy from the gas turbine also powers a steam turbine. Since IGCC power plants create two forms of energy, they have the potential to reach a fuel efficiency of 50 percent [source: U.S. Department of Energy].
Next, we'll learn about the most ambitious of all clean coal technologies and what needs to happen before clean coal can become commercially feasible.
We'll start by figuring out how much energy in kilowatt-hours the light bulb uses per year. We multiply how much power it uses in kilowatts, by the number of hours in a year. That gives 0.1 kW x 8,760 hours or 876 kWh.
The thermal energy content of coal is 6,150 kWh/ton. Although coal fired power generators are very efficient, they are still limited by the laws of thermodynamics. Only about 40 percent of the thermal energy in coal is converted to electricity. So the electricity generated per ton of coal is 0.4 x 6,150 kWh or 2,460 kWh/ton.
To find out how many tons of coal were burned for our light bulb we divide 876 kWh by 2,460 kWh/ton. That equals 0.357 tons. Multiplying by 2,000 pounds/ton we get 714 pounds (325 kg) of coal. That is a pretty big pile of coal, but let's look at what else was produced to power that light bulb.
A typical 500 megawatt coal power plant produces 3.5 billion kWh per year. That is enough energy for 4 million of our light bulbs to operate year round. To produce this amount of electrical energy, the plant burns 1.43 million tons of coal. It also produces:
Pollutant
Total for Power Plant
One Light Bulb-Year's Worth
Sulfur Dioxide - Main cause of acid rain
10,000 Tons
5 pounds
Nitrogen Oxides - Causes smog and acid rain
10,200 Tons
5.1 pounds
Carbon Dioxide - Greenhouse gas suspected of causing global warming
3,700,000 Tons
1852 pounds
It also produces smaller amounts of just about every element on the periodic table, including the radioactive ones. In fact, a coal-burning power plant emits more radiation than a (properly functioning) nuclear power plant!
In 1960, U.S. Secretary of the Interior Fred Seaton set aside 8.9 million acres (3.6 million hectares) in Alaska's northeast corner, calling it the Arctic National Wildlife Range. Seaton did this to protect the region's "unique wildlife, wilderness and recreational values" [source: U.S. Fish and Wildlife Service].
The famed refuge is home to many species of wildlife, including caribou, bears, musk oxen, sheep, wolves, moose and many others. Although the area appears to be a barren frozen wasteland during half of the year, it's often described as the "American Serengeti." Little did Seaton know that this wildlife refuge would fuel a heated controversy that remains unresolved to this day.
The controversy began in 1968 with the discovery of the largest oil field in North America in nearby Prudhoe Bay. Prudhoe Bay was developed as an oil-producing region, and the Trans-Alaska Pipeline was built to transport this oil down the length of Alaska from Prudhoe Bay all the way to Valdez, Alaska. Reserves of oil also were thought to exist within the Arctic National Wildlife Range at the time.
In 1980, President Carter signed the Alaska National Interest Lands Conservation Act (ANILCA), which doubled the size of the Arctic National Wildlife Range and renamed it the Arctic National Wildlife Refuge (ANWR). This act designated most of ANWR as wilderness and, therefore, protected it from oil and gas exploration. However, one small area remained a remote possibility. Dubbed Area 1002 (after section 1002 of the act), the region was open to exploration only if Congress were to authorize it.
Since 1980, many interested parties have been very curious about that authorization, especially since the U.S. Geological Survey estimated in 1998 that the area could contain as many as 16 billion barrels of oil [source: U.S. DOE]. Not surprisingly, Congress has faced numerous calls to authorize oil exploration and development in Area 1002.
Pro-energy groups say that drilling for oil in ANWR will help alleviate America's dependence on foreign oil. Environmental groups oppose disturbing this wilderness. This controversy has landed in the center of several presidential and congressional elections. Even Sen. John McCain and Gov. Sarah Palin disagreed on the issue during their 2008 bid for the U.S. presidency and vice presidency.
In this article, we'll explore ANWR's Area 1002, its potential oil reserves and its wildlife. We'll also look at how oil development in ANWR could affect world oil production and U.S. consumption. First, let's get a better picture of this disputed region.
Saturday, May 2, 2009
Chemistry: chemical reaction:
It is a process that always results in the interconversion of chemical substances.[1] The substance or substances initially involved in a chemical reaction are called reactants. Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions.
Different chemical reactions are used in combination in chemical synthesis in order to get a desired product. In biochemistry, series of chemical reactions catalyzed by enzymes form metabolic pathways, by which syntheses and decompositions ordinarily impossible in conditions within a cell are performed.
Types Of Chemical Reactions:
1)Combination Reaction:
It is a cChemical Reaction in which 2 or more substances combine to form a single substance.
It is a reaction in which a compound is decomposed into smaller compounds or elements:Eg: 2 H2O → 2 H2 + O2
3)Displacement Reaction:
It is characterized by an element being displaced out of a compound by a more reactive element:Eg: 2 Na(s) + 2 HCl(aq) → 2 NaCl(aq) + H2(g)
4)Double Displacement Reaction:
It is a reaction in which two compounds exchange ions or bonds to form different compounds:Eg: NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s)
5)Redox Reaction:
It is a reaction in which oxidation and redution takes place simontaneously.
Eg: 2 S2O32−(aq) + I2(aq) → S4O62−(aq) + 2 I−(aq)
6)Neutralization Reaction:
It is a reaction in which acid reacts with base to form salt and water.
Eg: NaoH+Hcl→Nacl+H2O.
7)Isomerisation Reaction:
It is a reaction in which a chemical compound undergoes a structural rearrangement without any change in its net atomic composition; see stereoisomerism
Biology:
Our Environment:
Environment- natural surroundings and external conditions of an organism, which
include all living and non-living factors that affect the organism
Organism- is the basic unit of an ecological hierarchy, can be unicellular such as
Amoeba and paramecium or multicellular such as humans
Population- a group of individuals of the same species inhabiting a given
geographical area at a particular time and functioning as a unit
Community- includes all individuals of different species living within a certain
geographical area Ecosystem- includes both living and non-living components of an area
Components of an ecosystem Abiotic factors- light, temperature, water, air etc.
Biotic factors- living organisms
Autotrophs- organisms that can manufacture their own food from inorganic
raw materials, also known as producers
Heterpotrophs- cannot synthesize their own food, are dependent on other
organisms
Herbivores- feed only on plants e.g., deer, horse, sheep etc.
Carnivores- eat other animals e.g., frog, cat, spider etc
Omnivores- feed on both plants and animals e.g. bear, monkey, man etc.
Decomposers- obtain nutrients by breaking down remains of dead plants and
animals, includes some bacteria and fungi
Functions of an ecosystem:
productivity- rate of production of organic matter (food) by producers
decomposition- breakdown of organic matter or biomass with the help of decomposers
Energy flow through an ecosystem
Trophic level - level of species in an ecosystem on the basis of the source of
nutrition
Producers- form the first trophic level, they manufacture food
trophic levels are connected through food chains
Food chain- a linear sequence of organisms in which each organism is eaten by
the next member in the sequence e.g.,
plants grasshopper frog snake eagle
Food web- interconnected network of food chains
10% law of energy transfer- only 10% energy is transferred from a lower
trophic level to a higher trophic level, which means that energy keeps on
decreasing as one moves up different trophic levels
Biomagnification- increase in the concentration of pollutants or harmful
chemicals with each step up in the food chain
Human influence on the environment:
Global warming- increase in the average temperature of the Earth’s surface
Greenhouse gases- CO2, CH4, O3, CFCs etc.
Ozone layer- present in the stratosphere, absorbs ultraviolet radiations
Ozone layer is getting depleted due to an increased concentration of chlorine
in the atmosphere- 3 2 Cl O ClO O Biodegradable wastes- produced mainly from plant and animal sources,
which can be broken down by living organisms
Non-biodegradable wastes- includes wastes such as plastic, metals etc.,
which cannot be broken down by living organisms BY PASS SURGERY (STENT) :
