Chapter 13 - N, P, and Biogeochemistry

Question 1

What causes N and P to enter water bodies?

Answer 1

Runoff

Question 2

Atmospheric nitrogen is converted to…? By what?

Answer 2

Nitrate by lightning

Question 3

Atmospheric N can be fixed as…? By what?

Answer 3

Organic N by bacteria and blue-green algae

Question 4

What greatly alters N cycle?

Answer 4

agricultural activity and fossil fuel burning

Question 4

Nitrate is returning to the atmosphere as what?

Answer 4

N2 gas

Question 5

N cycle in terrestrial system

Answer 5

Nitrification: Atmospheric nitrogen gets fixed by nitrogen-fixing bacteria of root nodules of legumes or nitrogen-fixing bacteria in the soil. Then, converted to ammonium (also produced from decomposers)
Denitrification: Ammonium is converted to nitrites via nitrifying bacteria. Nitrites are converted to nitrates by same bacteria. Nitrates are either taken up by plants or converted back to atmospheric nitrogen via denitrifying bacteria.

Question 6

Nitrogen speciation and their relationship to pH

Answer 6

NH3: lower pH = no NH3
NH4+: lower pH = lots of NH4+

Question 7

Adverse effects of ammonia

Answer 7

NH3 is a major excretory product of aquatic animals. If there are high concentrations of it already in the water, then it is difficult for the aquatic animals to excrete NH3. This could damage their gills, elevate their blood pH, and disrupt their enzyme and membrane systems

Question 8

Adverse effects of nitrite

Answer 8

Nitrite is more lethal than ammonia. Symptoms: Fish gasp for air at water surface, fish stay passive and limp near water outlets, brown gills and faster gill movement

Question 9

What is the most important nutrient?

Answer 9

Phosphorus

Question 10

Phosphorus characterisitics

Answer 10

Highly reactive and mostly found combined with other elements.

Question 11

Phosphorus cycle

Answer 11

P comes from (for example) phosphate extraction from mines (or fertilizer or erosion from phosphate rocks) and becomes apart of the runoff from river and streams. In the large body of water, P becomes dissolved phosphates. This is consumed excessively by algae and other photosynthetic organisms. Hypoxia’s story begins

Question 12

Mitigation strategies for eutrophication

Answer 12

Diversion of excess nutrients, altering nutrient ratios, physical mixing, and shading water bodies with opaque lining or water based stains