Download 5th Period Biogeochem Cycles

5th
Sulfur
1. Sulfur is found in the organic compounds of SO42- (from sea spray) H2S (from volcanoes)
and SOx
2. The two largest storage areas for sulfur are sedimentary rocks and the ocean.
3. One major human activity influencing the sulfur cycle is the burning of sulfur-containing coal
and oil in power plants, factories, and motor vehicles. These actions typically all add sulfur
dioxide back into the atmosphere, which will once again be released into the biotic environment.
Another major human activity influencing the sulfur cycle is the smelting (extraction of metal) of
sulfur-containing ores.
Nitrogen
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4.
Nitrogen is found in both nucleic and amino acids.
Nitrogen is fixed biologically and from human activity, such as industrial processes.
The following are the processes of the nitrogen cycle:
Nitrogen fixation is the conversion of gaseous nitrogen to ammonia (NH3) due to specialized,
nitrogen-fixing bacteria, such as cyanobacteria. These bacteria use an enzyme called nitrogenase
to split the nitrogen in order to combine it with hydrogen.
Nitrification is the conversion of ammonia or ammonium (NH4+) to nitrate (NO3-) by soil
bacteria. Different types of this bacteria convert ammonia/ammonium into nitrite (NO2-), and
then subsequently convert the product to nitrate. This process allows the bacteria to gain energy.
Ammonification is the process of nitrogen-containing waste products, such as urea or uric acids,
being broken down by ammonifying bacteria. This decomposition releases nitrogen as ammonia
back into the cycle.
Denitrification is the reduction of nitrate to gaseous nitrogen by denitrifying bacteria in low
oxygen or oxygen-free zones. These bacteria reverse the process of nitrogen-fixing bacteria, and
complete the nitrogen cycle by freeing up gaseous nitrogen to be used again for fixation.
One way humans influence the nitrogen cycle is through their use of commercial inorganic
fertilizer. The large quantities of nitrous oxide released not only affect the balance in the
atmosphere and nitrogen cycle, but also depletes the ozone layer and warms the troposphere.
Another anthropogenic intervention in the nitrogen cycle is made by burning fossil fuels. These
energy sources release large amounts of nitric acid into the atmosphere, and can also contribute
to the cause of acid rain.
Hydrological Cycle
1. The processes of evaporation, transpiration, condensation, precipitation, runoff, infiltration
and percolation occur in the hydrologic cycle. During evaporation, liquid water changes to a gas,
due to the heat in oceans and land. In transpiration, water that is taken from plants by
evaporation and is added back to the atmosphere. Condensation then changes water vapor to
liquid water. Condensation is responsible for the formation of clouds in the hydrologic cycle.
Precipitation occurs when water is released from clouds in the form of rain, snow, sleet or hail.
Precipitation provides the most water to Earth from the atmosphere. Runoff in the hydrologic
cycle has to do with the movement of land water to oceans, rivers, lakes, and streams. Runoff
consists of water that is not evaporated, transpired or water that goes under the surface and
becomes groundwater. Infiltration in the hydrologic cycle is when the water soaks into the
ground and moves into rocks through cracks and pore spaces. Lastly, percolation is when water
filters down through aerated soil due to gravity.
2. The two driving forces behind the water cycle is the sun's energy, which causes heat, and
wind, which moves runoff and water vapor in the water cycle.
3. Groundwater in the water cycle is water held underground in the soil, or in pores and crevices
in rocks. Aquifers are large underground water reservoirs that store water. Finally, the water
table is the level below which the ground is saturated with water. It’s located above the zone of
saturation and below the zone of aeration.
4. One significant anthropogenic intervention in the hydrologic cycle is irrigation using the
water for crops. Another is runoff from urbanization, this is building on land and using
cement causing more runoff. Lastly wetland drainage, this is getting rid of the wetlands so
now the water can’t be absorbed as much and it will cause more runoff.
Carbon Cycle
1. What 4 Organic compounds is carbon found in? Proteins, carbohydrates, lipids and nucleic
acids.
2. Carbon dioxide comprises approximately what percent of tropospheric gases? 0.04%
3. How is the relative amount (%) of CO2 significant in contributing to the Earth’s “natural
thermostat”? If the carbon cycle removes too much CO2 from the atmosphere, the
atmosphere will cool. If it generates too much, the atmosphere will get warmer.
4. Identify the two processes which have the greatest influence on tropospheric concentrations of
CO2 on a monthly or yearly basis. Photosynthesis and cellular respiration.
5. Name the two largest sinks (storage areas) for carbon. Sedimentary rocks and fossil fuels
6. Discuss how oceans play a major role in regulating CO2 levels in the troposphere. Some of the
atmosphere’s CO2 dissolves in the ocean and some photosynthesizing producers remove
some. Also, ocean water can put CO2 back in the atmosphere by warming the waters.
7. Describe the two major anthropogenic interventions in the carbon cycle. 1) Humans deplete
trees faster than they can reproduce 2) Adding CO2 into the atmosphere by burning fossil
fuels and wood.