Environmental Engineering Reference
In-Depth Information
phosphorous, through its use in fertilizers and detergents and its presence in untreated sewage; sulfur, in
coal combustion and industrial processes; and nitrogen, through extensive use of fertilizers, the com-
bustion of fossil fuels, and massive production of animal waste.
4.
B
Aquifers recharge slowly if there is inconsistent rainfall. Water percolates from the soil surface down
through soil and sediment, ultimately reaching the aquifer. With limited rainfall, this process is slow
and limits the amount of water that reaches the aquifer.
5.
B
Because fossil fuels are stored in the sediment of the Earth, when they are removed and then combus-
ted for energy, the carbon is emitted into the atmosphere. Deforestation and the removal of vegetation
also release carbon into the atmosphere in the form of carbon dioxide. Deforestation releases carbon di-
oxide into the atmosphere because trees act as carbon sinks, storing carbon. Once they are cut down, the
stored carbon is re-released. Conversion of carbon dioxide back into vegetation and eventually sedi-
ment is not happening at the same rate at which carbon is being removed, leading to a shift in the bal-
ance of carbon from sediment to atmosphere, and resulting in the current climate change.
6.
D
The ozone layer is located in the stratosphere, where it creates a shield against much of the harmful
ultraviolet radiation from the sun. Ozone emitted into or formed in the troposphere contributes to cli-
mate change.
7.
A
Soil porosity is the amount of space between soil particles and is expressed as the ratio of void space
to total volume. Water, air, and other gases fill these pore spaces. More pore space means a high water-
holding capacity.
8.
A
Radon and asbestos are both naturally occurring substances but can become indoor air pollutants.
Radon is a radioactive gas that can seep into basements from the surrounding bedrock. Because it is ra-
dioactive, chronic exposure can lead to negative health effects, including lung cancer. Asbestos is a
mineral with a fibrous crystal that is mined from the lithosphere. When inhaled, these fibers can lodge
in the alveoli of the lungs. The body then produces acids to fight the invasive particles, sometimes lead-
ing to diseases including mesothelioma and asbestosis.
9.
B
The Earth absorbs and slowly releases solar energy, warming air near its surface. This warm air is less
dense that cool air above, so the warm air rises. As it rises, it cools, thereby becoming denser and sink-
ing back toward the Earth's surface. This continual rising and falling creates convection currents.
10.
B
To calculate the doubling time of a population, use the equation 70 ÷ annual growth rate (in which
"percent" is removed from the growth rate). Therefore, if a population is growing at a rate of 1.4 per-
cent annually, the answer is found as follows: 70 ÷ 1.4 = 50. This means that the population will double
in 50 years.
11.
B
Populations of K-selected species usually stay near carrying capacity, competing for limited re-
sources. Fewer resources lead to a diminished carrying capacity. Although climate change may contrib-
ute to lack of food and water, it is this lack and not climate change itself that diminishes carrying capa-
city.
12.
C
Negative feedback loops are the most common in nature, as the inputs and outputs into a system sta-
bilize each other and create equilibrium. (For example, more of something "turns off" its production.)
Within positive feedback loops, a system moves in one direction, toward an extreme, and one reaction
causes another, which causes another, creating instability (like a snowball picking up more snow). Pos-
itive feedback loops in nature are usually due to human involvement. Examples include the changing
climate, melting of polar ice, erosion, and human population growth.
