Environmental Engineering Reference
In-Depth Information
• 1 point: CO
2
is a greenhouse gas that helps trap heat in the atmosphere. An increase in the concen-
tration of CO
2
will lead to an increase in the Earth's temperature over time, and a decrease in the
concentration will result in lower temperatures over time.
C. Describe two natural processes that occur in the carbon cycle. (2 points maximum)
• 1 point: In photosynthesis, energy is used to combine CO
2
with H
2
O to form glucose (C
6
H
12
O
6
)
and oxygen.
• 1 point: In cellular respiration, glucose (C
6
H
12
O
6
) in the presence of oxygen is burned to release
CO
2
and H
2
O and energy.
• 1 point: During the decomposition of dead organisms, CO
2
is released.
• 1 point: CO
2
exists in equilibrium between the water and atmosphere. Increasing CO
2
in the atmo-
sphere increases CO
2
in aquatic systems.
D. Describe two ways in which humans affect the carbon cycle. (2 points maximum)
• 1 point: As humans burn fossil fuels and biomass for energy, CO
2
is being released at an increasing
rate. This increases the amount of CO
2
in the atmosphere, which causes the concentration of CO
2
in
the oceans to increase. Carbon dioxide in the oceans forms carbonic acid, so with an increasing
amount of CO
2
in the oceans, more carbonic acid is formed, lowering the pH of the oceans.
• 1 point: The increase in CO
2
in the atmosphere may be leading to an increase in photosynthesis, in-
creasing plant life and, therefore, the concentration of oxygen in the atmosphere.
• 1 point: Burning of fossil fuels increases the amount of CO
2
concentrations in the atmosphere. CO
2
is considered a greenhouse gas, and greenhouse gases contribute to climate change.
• 1 point: Deforestation is causing an increase in CO
2
concentrations in the atmosphere because trees
and vegetation hold large amounts of CO
2
. As forests are cleared, CO
2
is released into the atmo-
sphere. CO
2
is considered a greenhouse gas, and greenhouse gases contribute to climate change.
E. Describe two ways humans impact other biogeochemical cycles. (2 points maximum)
• 1 point: In the phosphorus cycle, an increase in phosphorus into an aquatic system may result in an
increase in plant growth. This may lead to algae blooms, eutrophication, and potentially hypoxia.
• 1 point: Phosphorus can be introduced into an ecosystem through runoff containing detergents, raw
sewage, and fertilizers.
• 1 point: In the oxygen cycle, chlorine-containing compounds may cleave an oxygen molecule from
ozone, ultimately depleting the ozone layer. This can increase the amount of UV radiation reaching
Earth's surface, harming humans, animals, and plants.
• 1 point: Humans have altered the nitrogen cycle by artificially fixing nitrogen through the use of fer-
tilizers. This process, called the Haber-Bosch process, has almost doubled the amount of nitrogen
fixation that occurs.
• 1 point: The sulfur cycle has been altered in large part by the burning of coal, which emits SO
2
and
H
2
SO
4
. When they chemically react with components in the atmosphere, acid rain, pollution, and
smog can form.
4.
This question is worth a maximum of 10 points, as follows:
A. Explain how hydrogen is attained for use as an energy source. (2 points maximum)
• 1 point: Hydrogen gas needs to be isolated, as it does not exist on its own naturally.
• 1 point for one of the following methods:
