Week 5

Question 1

Beta-minus decay

Answer 1

a neutron breaks apart into a proton and a high energy beta- particle (an e-)
(n -> p + e)
beta particle on products side

Question 2

electron capture

Answer 2

not often
inner shell electron is captured by a proton to form a neutron (p+e- -> n)
beta particle on reactants side

Question 3

alpha decay

Answer 3

unstable nucleus ejects an a-particle that consists of 2 protons and 2 neutrons
common among high mass elements
result is 4 mass units less and 2 atomic numbers lower

Question 4

fission

Answer 4

unstable nucleus breaks apart into two smaller nuclides when hit by neutron bombardment
not natural, MUST BE HUMAN INDUCES

Question 5

Which isotopes are produced by decay of long-lived radionuclides from supernovae or Big Bang (e.g., U and Th series isotopes)?

Answer 5

Natural isotopes

Question 6

Which radionuclides are produces by interaction of cosmic rays with atmospheric or Earth surface materials?

Answer 6

cosmogenic radionuclides

Question 7

how can radionuclides be artificially produced?

Answer 7

nuclear reactors and weapons testing

Question 8

When were thermonuclear weapons exploded?

Answer 8

Late 1950s and early 1960s

Question 9

Primary productivity = how many mol O2/m^2/yr?

Answer 9

10 mol O2/m^2/yr

Question 10

______ is small with respect to gas exchange

Answer 10

primary production

Question 11

Rough estimate of deep ocean O2 consumption?

Answer 11

0.42 mol O2/m^2/yr

Question 12

Jahnk (1996) estimated total deep ocean (>1000m) ______ using enclosed incubation chambers deployed on the seafloor. On a per area basis, Jahnke found ____ mol O2/m^2/yr

Answer 12

respiration
0.3

Question 13

Because little org-C is buried in sediment, most of it is ________ in the water column. This indicated that only a small percentage of the _______ occurs in the deep ocean…

Answer 13

respired (remineralized)
respiration

Question 14

________ POC (Particulate Organic Matter) flux: >99.9% of OC is _____ before burial, ___% in the surface ocean

Answer 14

Martin et al. (1987)
respired
90% in the surface ocean

Question 15

Wyrtki (1962) hypothesis: O2 min is determined by a _____________

Answer 15

balance between respiration and resupply by physical processes

Question 16

Wyrtiki’s Other Model
Alternative hypothesis: Low O2 waters formed along ______ where productivity (and hence bottom O2 respiration) is high. These low O2 waters are then advected horizontally throughout the ocean along isopycnals.

Answer 16

continental margins

Question 17

Where is respiration the highest?

Answer 17

Surface ocean

Question 18

O2 minimum results from a balance between O2 removal via ____ and O2 supply via physics near poles

Answer 18

respiration

Question 19

____ is both of organic matter settling through the water column (vertically) and respiration occurring in continental margin sediments (horizontally)

Answer 19

respiration

Question 20

When O2 is low, what other oxidants can bacteria use?
What are the various oxidants called?

Answer 20

NO3 -, SO4 2-, MnO2, FeOOH, and fermentation
The various oxidants are called terminal electron acceptors

Question 21

The Feq (flux, in mol/m^2/yr) of O2 into the ocean at -10 degrees celsius is _______ compared to the Feq of O2 into the ocean at 10 degrees celsius

Answer 21

less than or zero

Question 22

The flux of O2 into the surface ocean is approximately 440 mol/m^2/year. How does this compare to the rate of O2 produced by photosynthesis by plants in the surface ocean?

Answer 22

photosynthesis produces much less

Question 23

Where in the surface ocean are concentrations of oxygen gas NOT supersaturated with respect to atmospheric oxygen?

Answer 23

equatorial zones and areas of high upwelling, such as off the west coast of North America

Question 24

The oxygen minimum zone occurs between __ to ___ m depth

Answer 24

700 to 1500

Question 25

what produces oxygen in the surface ocean?

Answer 25

photosynthesis

Question 26

how much oxygen is in equatorial surface waters?

Answer 26

not a lot; low

Question 27

What is the zone of largest temperature change?

Answer 27

thermocline

Question 28

where is the highest deep water oxygen found?

Answer 28

North Atlantic

Question 29

What is the process that uses up oxygen?

Answer 29

Respiration

Question 30

oxygen ___ in deep waters during its trip from Atlantic to Pacific

Answer 30

decreases