PDS APES 5th Period 2009-10

Today in class, we continued talking about the secondary effects of car exhaust and coal burning.  Today we spent the day talking about the formation/affects of acid rain in particular.

Acid rain in a problem in the troposphere, and is therefore a regional problem.  Even though acid rain has always been referred to as “rain,” a more appropriate term is Acid Deposition, or, to deposit acid.  This is because not all acid comes from rain.  There are two types of acid: Wet Acid and Dry Acid.  Wet acid comes from any form of precipitation that involves water, be it snow, rain, sleet, or fog.  Dry acid is the deposit of particles of acid (dusts or salts).  Whether the acid coming from the sky is wet or dry, it is always considered acid when it is more acidic than natural rain water (has a lower pH than 5.6).

Acid Rain is created (indirectly) when sulfur dioxide and nitrogen oxides are emitted into the atmosphere.  These gases can be emitted through the burning of coal, and from the use of gasoline-burning cars.  After the gases are emitted into the atmosphere, they react with the water droplets in clouds and in the air, creating a series of different reactions.  Here are three naturally occuring reactions that form acid rain: SO2+H2O=H2SO3; SO3+H2O=H2SO4; and 2NO2+H2O=HNO3+HNO2.  After reactions occur, acid falls from the sky in either the form of wet or dry acid deposition.  Here is a visual of the acid rain process:

http://www.odec.ca/projects/2008/shar8a3/AcidRain_drawing.gif

The effects of acid rain are detrimental.  Acid rain directly affects plant and animal tissue, dissolving away protective membranes.  It also directly affects monuments and buildings by breaking them down and dissolving them quicker than the natural decomposition rate.  Acid rain also lowers the pH of lakes and streams.  Indirectly, acid rain leaches soil of its vitamins and minerals, leading to lack of nutrition for plants.  It also “frees” heavy metals, and mobilizes them, which leads to fish suffocation when the heavy metals enter a pond or stream.  A final indirect affect of acid rain is the decay of the waxy membrane coating the surface of leaves on plants.  This leaves the plant more susceptible to freeze, dry up, or get killed by insects.  Here is an affect of acid rain:

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http://www.solcomhouse.com/images/800px-Acid_rain_woods1.jpg

There are two major solutions for acid rain: Prevention and Clean Up. Acid rain can by prevented by burning low sulfur coal, washing and treating coal before use, using scrubber technology on power plants, using the cap and trade industry, and by using and burning less sulfur in gas.  Clean up of acidic rain is much more expensive, and one of the main ideas is to add lime to lakes, in order to make the lake less acidic.

I hope this helped!

Today in class, we discussed the properties of Uranium, as well as how it is used in nuclear power plants.

Of all the naturally occurring atoms on Earth, Uranium is the largest in size.  Because of its large size, Uranium is very unstable, and very reactive.  In order to stabilize itself, Uranium (and any other large, unstable atoms) must release matter and/or energy.  There are two types of matter an atom can release: alpha and beta.  Alpha Decay occurs when an atom releases a proton or neutron to stabilize itself, and Beta Decay occurs it releases electrons.  An atom can also release energy, or Gamma Rays.  Unstable atoms naturally release one, two, or all of these three, causing the atom to decay over time.  Given time, Uranium will naturally decay until it becomes the stable lead atom.  An atom is considered radioactive when it constantly releases matter or energy.

A Half Life of an atom is the time period that it takes for half a sample of that atom to decay into a nonradioactive, or stable state.  Uranium 235 has a half life is 710 million years.

Because Uranium is the largest atom, and therefore the most likely to decay, it is also the most radioactive of all the atoms.  This comes in handy with nuclear power plants, which use Nuclear Reactors to create energy from Uranium.

When finding the Uranium to use in nuclear reactors, the only isotope of Uranium that can be used is Uranium-235.  An Isotope is an atom that has the same number of protons, but a different number of neutrons.  The number that follows the atom name (235) is the number of neutrons that the particular isotope has.  Although Uranium-235 is the main source of fuel used, it is also one of the smallest Uranium amounts found in nature (less than 1%).

Nuclear Fission is the atomic process that powers nuclear reactors.  Nuclear fission occurs when the nuclei of a large atom is hit by a neutron, and therefore split, producing a split atom and another free neutron.   A Nuclear Fission Chain Reaction occurs when the neutron that was produced by the original nuclear fission hits another atom’s nucleus, producing more free neutrons, and therefore the chain continues.

The Chain Reaction produces a LOT of heat, which is used to power the nuclear reactors.  In nuclear reactors, Fuel Rods (Uranium) and Control Rods (neutron control) are placed in a containment building.  The fuel rods are placed in a huge vat of water, and when the chain reaction occurs (the speed of which can be controlled by the control rods, which absorb or release neutrons) the water is heated.  The water in the vat then boils, turning into steam.  The steam is sent through Steam Pipes/Heat Exchangers, which use the steam to spin a Turbine, creating energy.  All the steam then travels to the cooling tower, where excess heat is vented through steam stacks.  There are no pollutants released from nuclear Power plants. Here is a cite explaining nuclear reactors in more detail:  http://www.howstuffworks.com/nuclear-power.htm

http://electricalandelectronics.org/wp-content/uploads/2008/10/nuclear-power-plant.jpg

After fuel rods are used, they are still very radioactive, and must be placed securely in storage for hundreds of years.  If not placed in storage, radioactivity can be very harmful to human health.  Released alpha particles are not strong enough to get past the outer layer of human skin, but can cause skin cancer.  Beta particles are a little stronger, and can pass to the epidermal, or inner layer of skin.  Gamma Rays are nasty, and can pass through any type of tissue, bone included.  This is useful for treating diseases like cancer, but harmful in any other way.

I hope this helps!

So, I was reading through the book and got to the section that talked about China’s population/population control.  It said that China’s fertility rate had decreased to 1.6 children per mother by 2007, but that the population wasn’t expected to level off until around 2050.  How does that happen? I thought that the replacement rate was 2.1, and if China is way under it, shouldn’t their population level off and start declining now?  Is it  just immigration?

So this is pretty random, but I was looking through the study guides and got to the question that asked about the difference between mass and background extinction.  In my answer I had that background extinction is basically happening all the time and that there have been five mass extinctions in Earth’s history, but I was wondering, if you’re alive during a mass extinction, would you know it,seeing as they take place over millions of years? I don’t mean to sound morbid or anything, but I remembered that during the mass extinction video, scientist were wondering whether or not we are in a sixth mass extinction phase, and I didn’t know if we would know if we were or not.

Today in class,  we talked more about ecological niches.  Like Emily said, a niche  is an organism’s “role” or “job” in an ecosystem.  Niches can be formed  by looking at an organism’s trophic level, role in the food web, role in energy flow, its interaction with other organisms, and its use of resources.

Like Emily also mentioned, there is a Competitive Exclusion Principle that causes adaption of on organism’s niche.  This principle states that if two species live in the same ecosystem and the same niche, once will be excluded.  Or as Bobbie Hinson says, the species will have to “adapt, migrate, or die.”  This principle forces specialized species, and splits the niches into fundamental niches and realized niches.

The two major types of niches that we talked about  today, Fundamental Niche and Realized Niche.

A Fundamental Niche is the whole range under which an organism can exist in a niche without the presence of competition.  For instance, a sea gull can easily survive on a beach, and is adapted to flying and hunting fish from the air, and is also adapted to feeding off crabs and clams on the beach.  The seagull’s fundamental niche, therefore, is the beach, because it can survive in a wide range of condition.  Typically, the terms Fundamental Niche and Generalist Species go hand in hand.  A Generalist Species is one that can easily live pretty much anywhere, or is adapted to survive in the most common environments.  In the sea gull scenario, the sea gull is the generalist species  in a fundamental niche.  Other common generalist species are pigeons, crows, and cockroaches, because they can easily survive in many different places.

A Realized Niche is a forced niche, where an organism is forced to live due to competition.  Usually, species that live in realized niches are specialized to live in just that area, and have adapted specially to decrease competition.  For example, a plover is a bird that lives on sandy beaches.  It has a short beak, long legs (compared to its body size), and amazing vision because, unlike the other sea birds, the plover hunts through sight, then runs to its prey.  It doesn’t need a long beak because it doesn’t dig around in the sand looking for food, it simply sees it from the surface.  The plover is specially adapted to fit its realized niche, which is a sea shore.  In this scenario, the plover is a Specialist Species, or a species that has adapted especially for a particular environment.  A Realized Niche and a Specialist Species typically go together.

The sea gull has a wide range of adaptions while the plover has distinct, specialized adaptations.

Other Niche Descriptors include Keystone Species, Foundation Species, and Indicator Species

Keystone Species are species that have more of an impact on the ecosystem then they do abundance.  In other words, although there may be a limited number of individuals of each keystone species (they are usually in higher trophic levels) they affect multiple other species in their ecosystem, and provide biodiversity.  Examples include sea stars, kangaroo rats, sea otters, and pollenators.

Foundation Species are typically dominant photosynthesizers in an ecosystem.  They provide food and shelter for many different organisms.  Examples include kelp and oak trees.

Indicator Species are species that are sensitive to changes in the environment, and indicate the environmental change my migrating or dying.  For instance, trout numbers indicate the dissolved oxygen in water, amphibian health indicates water quality, and bird migrations indicate the quality of air.

The last thing we talked about today was whether a species is Native or Non-Native.  Pretty self-explanatory, native species are species that are from, or originally adapted to the environment it is living in (synonyms include indigenous species and endemic species).  Non-native species are new species, because they either migrated or were moved to a new environment (synonyms include alien, invasive, exotic, foreign, and if they are moved to a new place because humans put them in the new place, they are called introduced species).

Thats what we covered in class in a nutshell, if anything was confusing, wrong, or I missed anything feel free to comment

I’m looking over a worksheet that we received in class that has a chart of the four layers of the atmosphere and the temperatures of each layer. I understand why the temperature decreases in the troposphere as you go higher, but why does it vary, increasing and decreasing as it does, the higher you travel in the atmosphere?

Alright, I know that we didn’t go over the hydrologic cycle in class just because it’s been covered so many other times, but looking over question 23 in the study guide and the section in the book explaining the water cycle, I’m still not sure what infiltration and percolation are.  Is it the process of water soaking into the soil then slowly traveling to the aquifers?  If so then what is the difference between the two?

I read Emily’s question about natural income vs capital, but even with Michael’s answer I’m still not completely sure what natural income is. Is it the same thing as renewable resources?