Question

which of the following is the best explanation for why there is such a small amount of phosphorus that moves into aquatic systems?
a phosphorus is highly stable in the atmosphere and remains there for long periods of time.
b the amount of phosphorus in the cycle has been greatly reduced because of the use of catalytic converters in automobiles.
c there is not a gaseous phase of the phosphorus cycle, and therefore the movement of phosphorus into oceanic reservoirs is very slow.
d the phosphorus cycle occurs so rapidly that it does not exist in any one reservoir for a very long time.

Explanation:

• Option A: Phosphorus is not highly stable in the atmosphere. In fact, it has no significant gaseous phase in its cycle, so this option is incorrect.
• Option B: Catalytic converters in automobiles are related to reducing pollutants like nitrogen oxides and carbon monoxide, not phosphorus. This option is not relevant to the phosphorus cycle in aquatic systems.
• Option C: The phosphorus cycle is a sedimentary cycle. There is no gaseous phase of phosphorus. Phosphorus mainly moves from land (through weathering of rocks) to water (aquatic systems) at a slow rate as it has to go through processes like runoff and sedimentation. This explains the small amount of phosphorus moving into aquatic systems.
• Option D: The phosphorus cycle is relatively slow - it is a sedimentary cycle with long - term storage in rocks and sediments. So, the claim that it occurs rapidly is wrong.

Answer:

C. There is not a gaseous phase of the phosphorus cycle, and therefore the movement of phosphorus into oceanic reservoirs is very slow.