L15 - Biogeochemistry

Question 1

What is biogeochemistry?

Answer 1

Refers to the cycling of chemical elements through living and dead parts of the Earth system. Can be global or local in scale, and cycles are connected.

Question 2

which boundaries are still in safe operation?

Answer 2

Stratospheric ozone depletion, ocean acidification and atmosphere aerosol loading

Question 3

In which biome is most carbon stored?

Answer 3

Tropical/subtropical forests, followed by boreal and temperate forests

Question 4

Nitrogen fixation

Answer 4

process by which N2 is converted into biologically available N (occurs via bacteria/archaea or lightning which breaks the triple bond)

Question 5

Nitrification (ammonium oxidation)

Answer 5

microbial process by which ammonia is sequentially oxidised to nitrite (NO2-)and nitrate (NO3-).

Question 6

Nitrogen mineralisation (ammonification)

Answer 6

where microbes break N compounds from organic material into simple substances such as ammonia

Question 7

Denitrification

Answer 7

conversion of nitrate to nitrogen gas by bacteria under anaerobic conditions (but nitrate formed in aerobic conditions)

Question 8

When is denitrification unwanted?

Answer 8

Agriculture as loss of nitrate in fertiliser is detrimental and costly

Question 9

When is denitrification wanted?

Answer 9

During water treatment to remove unwanted nitrates from wastewater effluent

Question 10

Why is there P limitation in the tropics?

Answer 10

• Because Fe and Al rich soils bind strongly to P (monodentate or bidentate bonding) to form inner sphere complexes, thus P is not available for use. Occurs on goethite surface
• Also due to high soil erosion and leaching which washes P out of soil profile