Week 5 Flashcards
Beta-minus decay
a neutron breaks apart into a proton and a high energy beta- particle (an e-)
(n -> p + e)
beta particle on products side
electron capture
not often
inner shell electron is captured by a proton to form a neutron (p+e- -> n)
beta particle on reactants side
alpha decay
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
fission
unstable nucleus breaks apart into two smaller nuclides when hit by neutron bombardment
not natural, MUST BE HUMAN INDUCES
Which isotopes are produced by decay of long-lived radionuclides from supernovae or Big Bang (e.g., U and Th series isotopes)?
Natural isotopes
Which radionuclides are produces by interaction of cosmic rays with atmospheric or Earth surface materials?
cosmogenic radionuclides
how can radionuclides be artificially produced?
nuclear reactors and weapons testing
When were thermonuclear weapons exploded?
Late 1950s and early 1960s
Primary productivity = how many mol O2/m^2/yr?
10 mol O2/m^2/yr
______ is small with respect to gas exchange
primary production
Rough estimate of deep ocean O2 consumption?
0.42 mol O2/m^2/yr
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
respiration
0.3
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…
respired (remineralized)
respiration
________ POC (Particulate Organic Matter) flux: >99.9% of OC is _____ before burial, ___% in the surface ocean
Martin et al. (1987)
respired
90% in the surface ocean
Wyrtki (1962) hypothesis: O2 min is determined by a _____________
balance between respiration and resupply by physical processes
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.
continental margins
Where is respiration the highest?
Surface ocean
O2 minimum results from a balance between O2 removal via ____ and O2 supply via physics near poles
respiration
____ is both of organic matter settling through the water column (vertically) and respiration occurring in continental margin sediments (horizontally)
respiration
When O2 is low, what other oxidants can bacteria use?
What are the various oxidants called?
NO3 -, SO4 2-, MnO2, FeOOH, and fermentation
The various oxidants are called terminal electron acceptors
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
less than or zero
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?
photosynthesis produces much less
Where in the surface ocean are concentrations of oxygen gas NOT supersaturated with respect to atmospheric oxygen?
equatorial zones and areas of high upwelling, such as off the west coast of North America
The oxygen minimum zone occurs between __ to ___ m depth
700 to 1500
