PDS AP Environmental Science 8th Period 2010-11

I do not understand how nitrogen can produce both primary and secondary pollutants.
Also, how in depth do you think we should know the process of  scrubbers?

Good luck studying for the last test!

China began planning to build the Three Gorges Dam along the Yangzi River in 1919 by Sun Yatsen. Although planning took decades, this monumental dam (the world’s largest hydroelectric dam) is finished with most construction, and hopefully it will be in maximum use within a couple of years.

China's Three Gorges Dam

In a hydroelectric dam, the flow of water is used to turn turbines to create electricity. The Three Gorges Dam is an example of a storage system because water is stored in reservoirs formed by a dam.

The Three Gorges Dam is a mile and a half wide and more than 600 feet high. The reservoir created is 400 miles long and hundreds of feet deep. For half a year, this reservoir allows 10,000 ton freighters to sail to China’s interior. The electricity produced also equals 18 nuclear power plants! This is a form of renewable energy. It is hoped that this dam will benefit both international trade and the increasing need for electricity.

Here is a general information video.

This all sounds great doesn’t it? Well there are many serious consequences of building this hydroelectric dam. The negative impacts range from environmental to social.

Some negative effects include:

• Toxic materials leach into reservoir
• Destruction of landscape
• Destruction of homes (more than 100 towns)
• 1.2 million people relocated
• Destruction of archeological sites (around 1,300 sites)
• Loss of farm land
• Silt accumulation

There are even questions about how efficiently the hydroelectric energy will be used. It is stated by government officials that as much as 1/9 of China’s electricity could come from the Three Gorges Dam-the 26 hydropower turbines will produce 18.2 million kilowatts.

To watch a video of the negative impacts, click here.

It is now up to you to decide how beneficial you think this dam will really be for China.

You can read more information from CNN.

So I have a couple questions overall and then one for Mr. Willard…

Mr. Willard:
How much should we know about the different aquatic life zones between the two chapters? The study guide said that we would get a review sheet for them but I don’t think I have one.

Sorry for so many questions! Good luck studying!

I am having some trouble seeing the difference between the LD50 and the LC50. I believe what we actually did in class was a LC50 lab. Is the only difference the way the toxin was taken in by the body? Also, what is the difference between the threshold dose and the TDLO? Thanks!

How can you tell if a country might be sliding back to stage 1 or is in stage 3. Both populations seem to be staying fairly constant for age groups under 20 or so. Is the difference that a “sliding” country would have more population at a younger age that is constant than the decreasing older generations (this kinda looks like a trouble game piece) and a stage 3 country would have less people at the younger ages but still with a constant growth rate(this would make a shape like a mushroom)?

In the paradox of enrichment, why does this only happen when the growing season is longer (or does it)? When we ran the short growing season, the population sizes dropped significantly but did not go extinct. Why? If there was a decrease in the food supplies, then wouldn’t there be less food for both prey and predator, leading to both populations going extinct? Thanks for all the help!

I think I understand how aquifers work, and how they contain groundwater. But is the aquifer/groundwater the lithospheric stage for the water cycle? I know how water travels between the other three spheres but I am not sure how it can really be in the lithosphere and in rock. Thanks for the help!

What is the difference between an arctic grassland tundra and an alpine tundra? The textbook briefly mentions alpine and does  not specially mention arctic grassland. They seem to be grouped together for nearly everything. Is the alpine higher than the arctic grassland? There are abiotic and biotic factors nearly the same (as it would appear to me)? Lastly, is alpine the only one on the very top of a mountain?

Today in class we began our discussion on Earth’s atmosphere. Earth’s atmosphere is mainly comprised of nitrogen gas at 78%. N₂ is an inert gas (a gas that is non-reactive under normal situations) that does not natural affect humans. Decomposers put nitrogen gas into a useable form through the 3 reactions in the nitrogen cycle: nitrogen fixation, nitrification, and denitrification. The next gas that is in the atmosphere is oxygen, which makes up 21% of our air. O₂ is very different compared to N₂, because oxgyen is highly reactive. O₂ can be split by sunlight to make ozone, which is crucial for people on Earth. The last 1% of the atmosphere is made up primarily of Argon, and there are many other permanent gases (Ne, He, H₂, Xe) and variable gases (H2O, CO₂, CH₄, O₃) that can be found in very small percentages. The percentage of water vapor can vary between 0-4% depending on where it is (the desert would be closer to 0%, while the rainforest would be closer to 4%).

(top picture) http://www.asc-csa.gc.ca/eng/educators/resources/spacesuit/composition.asp

(bottom picture) http://www.aerospaceweb.org/question/atmosphere/atmosphere/layers.gif

The Earth’s atmosphere can be divided into 4 layers, but we will mainly focus on the troposphere and the stratosphere. The atmospheric layers are only about 1/100th of the Earth’s diameter. The first, bottommost layer is the troposphere; this is where weather and human life occur. A nickname for the troposphere is the “weather maker.” The tropopause marks the boundary between the troposphere and the stratosphere. The temperature also starts to raise again after this point until you reach the stratopause. The next layer, the stratosphere, is primarily made up of the ozone layer. The reason that the temperature begins to raise after the tropopause and until it reaches the stratopause, is because in the ozone layer scatters UV rays. Without the ozone layer scattering UV radiation, human life would cease to exist. A nickname for the ozone layer is  ”global sunscreen.”

As you go further up in the atmosphere, pressure decreases because there is less gravity to pull down the air molecules. The concentration of air molecules will increase as the altitude decreases. This is crucial when climbing mountains; if a person climbs too high, the air will get thinner, with less air molecules to breathe. If you were to climb to the top of  Mount Everest, you would be above 2/3 of the air molecules. 99% of the air molecules are below 50% of the atmospheric layers. The atmospheric pressure is 14.7 lb/in² at sea level.

Relative humidity is the ratio of the amount of water vapor actually in the air to the maximum amount of vapor required for saturation at the particular temperature. The relative humidity would be higher on a tropical island than at the desert. High humidity feels hotter to our bodies because it affects the ability of the air to evaporate our sweat. When the humidity is higher, there is more water vapor in the air. This means that it will take longer to evaporate sweat, which we need in order to cool our bodies.

http://en.wikivisual.com/index.php/Air